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2026-06-05T20:26:46Z

2024-10-03T10:05:34Z

Admin:

== Translate ==
[[File:vex_offset_position.gif | 340px | right]]

Offset the position of geometry

[[:File:vex_offset_position.hiplc|vex_offset_position.hiplc]]
<syntaxhighlight lang='C'>
@P += {1, 0, 0};
</syntaxhighlight>

== Taper ==
[[File:taper_vex_001.gif | 340px | right]]

Reduces the circumference by scaling along the XZ plane based on the height of the geometry.

[[:File:taper_vex_001.hiplc|taper_vex_001.hiplc]]

<syntaxhighlight lang='C'>
float taper = relbbox(0,@P).y;
// Remap the taper range
taper = fit01(taper, 1, fit01(sin(@Time*PI/5)*0.5+0.5, 2.5, .5));
// Apply the taper by scaling along the X and Y axis
@P *= set(taper,1,taper);
</syntaxhighlight>

== Boxify ==
[[File:vex_boxify_001.gif | 340px | right]]

Distorts the geometry, morphing it into a box shape

[[:File:vex_boxify_001.hiplc|vex_boxify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, @P+clamp(normalize(@P)*1.75,vector(-1),vector(1)) * (1.0-length(max(abs(@P)))), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Spherify ==
[[File:vex_spherify_001.gif | 340px | right]]
Distorts the geometry into a sphere shape

[[:File:vex_spherify_001.hiplc|vex_spherify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, normalize(@P), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Stretch ==
[[File:vex_stretch_001.gif | 340px | right]]
Stretch the geometry across it's X axis

Add one component of position to itself to stretch the geometry away from it's center. You can control the amount of stretching by multiplying the position before adding it to itself.

[[:File:vex_stretch_001.hiplc|vex_stretch_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
@P -= centroid;
@P.x += @P.x*chf('amt');
@P += centroid;
</syntaxhighlight>

== Shape Blending ==
[[File:vex_position_blend.gif | 340px | right]]
Blend between point attributes to produce a morph effect

[[:File:vex_position_blend.hiplc|vex_position_blend.hiplc]]
<syntaxhighlight lang='C'>
@P = lerp(@P, @opinput1_P, chf('blend'));
@N = lerp(@N, @opinput1_N, chf('blend'));
</syntaxhighlight>

== Snap to Grid ==

[[File:vex_snap_to_grid.gif | 340px | right]]
Snap ([https://en.wikipedia.org/wiki/Quantization_(signal_processing) quantize]) point positions to a grid for a downres effect

[[:File:vex_snap_to_grid.hiplc|File:vex_snap_to_grid.hiplc]]
<syntaxhighlight lang='C'>
float grid_scale = chf('grid_scale');
@P = rint(@P*grid_scale)/grid_scale;
</syntaxhighlight>

== Make 2D ==
[[File:vex_setcomp.gif | 340px | right]]

You can use the setcomp function to zero out a component of a vector, resulting in a two dimensional surface.

[[:File:vex_setcomp.hiplc|vex_setcomp.hiplc]]
<syntaxhighlight lang='C'>
// Set the X component to zero, planar 2D in YZ
setcomp(@P, 0, 0);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Y component to zero, planar 2D in XZ
setcomp(@P, 0, 1);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Z component to zero, planar 2D in XY
setcomp(@P, 0, 2);
</syntaxhighlight>

== Swizzle Coordinate System ==
[[File:vex_swizzle_vector_components.gif | 340px | right]]

Shuffle the components of a vector using [https://www.sidefx.com/docs/houdini/vex/lang.html#dot-operator swizzle]

[[:File:vex_swizzle_vector_components.hiplc|vex_swizzle_vector_components.hiplc]]
<syntaxhighlight lang='C'>
@P = @P.zyx;
</syntaxhighlight>


== Twirl ==
[[File:vex_twirl.gif | 340px | right]]
Twirl the geometry around the Y axis

[[:File:vex_twirl.hiplc|vex_twirl.hiplc]]

<syntaxhighlight lang='C'>
float a = chf('angle') * length(@P * {1, 0, 1});
float u = atan2(@P.x, @P.z);
float r = length(@P * {1, 0, 1});
@P = set(sin(u-a), @P.y, cos(u-a)) * set(r,1,r);
</syntaxhighlight>



== Peak ==
[[File:vex_push_surface_along_normals.gif | 340px | right]]
Move the surface along it's normals, producing an inflation effect

[[:File:vex_push_surface_along_normals.hip|vex_push_surface_along_normals.hip]]

<syntaxhighlight lang='C'>
@P += normalize(@P) * chf('scale');
</syntaxhighlight>

== Exploded View ==
[[File:vex_exploded_view.gif | 340px | right]]
Moves each packed piece outward from the geometry centroid

[[:File:vex_exploded_view.hiplc|vex_exploded_view.hiplc]]

<syntaxhighlight lang='C'>
@P += (@P - getbbox_center(0)) * chf('scale');
</syntaxhighlight>

== Point Jitter ==
[[File:vex_point_jitter.gif | 340px | right]]
Move each point in a random direction with a spherical distribution

[[:File:vex_point_jitter.hip|vex_point_jitter.hip]]

<syntaxhighlight lang='C'>
@P += sample_sphere_uniform(rand(@elemnum+chf('seed'))) * chf('scale');
</syntaxhighlight>

== Plexus Effect ==
[[File:vex_plexus.gif | 340px | right]]
Connect nearby points

[[:File:vex_plexus.hiplc|vex_plexus.hiplc]]
<syntaxhighlight lang='C'>
foreach(int pt; nearpoints(0, @P, 0.15, 10)) {
if(pt > @ptnum)
addprim(0, 'polyline', @ptnum, pt);
}
</syntaxhighlight>

== Connect to Nearest Point ==
Draw a line to the closest point of the second input
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, vector(point(1,'P',nearpoint(1,@P)))) );
</syntaxhighlight>

== Connect to Closest Surface Position ==
Draw a line to the closest surface position
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, minpos(1,@P) );
</syntaxhighlight>

== Randomize the Rotation of Packed Primitives ==
Update the transform intrinsic to a random orientation
<syntaxhighlight lang='C'>
vector r = sample_direction_uniform(rand(@primnum));
matrix3 x = primintrinsic(0,'transform',i@primnum);
rotate(x, PI*pow(rand(@primnum-666),0.5), r);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Randomize the Scale of Packed Primitives ==
Update the transform intrinsic to a apply a random scale
<syntaxhighlight lang='C'>
vector s = rand(i@primnum);
s = s.yyy; // Uniform Scale
matrix3 x = primintrinsic(0,'transform',i@primnum);
scale(x, s);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Random Color from Normal Direction ==
[[File:vex_rand_color_from_normal_direction.gif | 340px | right]]
Generate random colors based on the surface normal, adjust the multiplier to control the amount of colors

[[:File:vex_rand_color_from_normal_direction.hiplc|vex_rand_color_from_normal_direction.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = rand(rint(@N*2));
</syntaxhighlight>

== Group Unshared Edges ==
<syntaxhighlight lang='C'>
int isBorderEdge(int pt0, pt1) { // test border using half edges
int hedge = pointhedge(0, pt0, pt1); // try finding hedge
if (hedge == -1 ) {
hedge = pointhedge(0, pt1, pt0); // try reversed hedge
if (hedge == -1 ) return -1; // invalid hedge
}
return hedge_equivcount(0, hedge) == 1; // 1 if border edge
}

int pps[] = primpoints(0,@primnum); // current primitive's points
for(int i = 0; i<len(pps); i++) {
int pt0 = pps[i]; // current pt
int pt1 = pps[(i-1)%len(pps)]; // next point
if( isBorderEdge(pt0, pt1) ) { setpointgroup(0, 'border', pps[i], 1); }
}
</syntaxhighlight>

== Iterative Face Insetting ==
Recursive divide and inset edges, [https://twitter.com/d_gfx/status/1452718124579520512 via @d_gfx], excellent use of [https://www.sidefx.com/docs/houdini/vex/arrays.html arrays]
<syntaxhighlight lang='C'>
int pts[] = primpoints(0,@primnum); vector pos[];
int edge_div_pts[]; vector edge_div_pos[];
foreach( int pt; pts )
append(pos, vector(point(0,'P',pt)));
for( int i = 0; i < chi('iterations'); i++ ) {
resize(edge_div_pts,0); // empty
resize(edge_div_pos,0); // empty
for( int j = 0; j < len(pts); j++ ) {
append(edge_div_pos, lerp( pos[j], pos[(j+1)%len(pts)], chf('div_ratio') ));
append(edge_div_pts, addpoint(0, edge_div_pos[-1])); // [-1] grabs the last item from an array
}
for (int k = 0; k < len(pts); k++ ) {
addprim(0, 'poly', pts[k], edge_div_pts[k], edge_div_pts[(k+2)%len(pts)]);
}
pts = edge_div_pts;
pos = edge_div_pos;
}
addprim(0, 'poly', edge_div_pts);
removeprim(0,@primnum,1); // Remove the input prim and any points belonging to it
</syntaxhighlight>

== Iridescent Color Function ==
[[File:vex_iridescent.gif | 340px | right]]

Produce an iridescent color ramp from any varying value, [https://www.shadertoy.com/view/XlcBR7 from shadertoy]

[[:File:vex_iridescent.hiplc|vex_iridescent.hiplc]]

<syntaxhighlight lang='C'>
float amt = dot(@N, set(0,1,0))*0.5+0.5;
v@Cd = (0.5 + 0.5 * cos( PI*2*( amt + set(0,1,2)/3) ) );
</syntaxhighlight>

== Rainbow Colors from HSV Colorspace ==
[[File:vex_hsvtorgb_rainbow_001.gif | 340px | right]]

You can easily control the hue, while keeping the saturation and value the same using the [https://www.sidefx.com/docs/houdini/vex/functions/hsvtorgb.html hsvtorgb] function.

This allows you to easily create rainbows, gradients, perform hue rotations and produce complimentary colors.

[[:File:vex_hsvtorgb_rainbow_001.hiplc|vex_hsvtorgb_rainbow_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb( set(relbbox(0,@P).z - @Time/5 + dot(@N,set(0,1,0))/2, 1, 1));
</syntaxhighlight>

== Rainbow Cycle with frac function ==
[[File:rainbow_cycle_w_frac_VEX.gif | 340px | right]]

Using the [https://www.sidefx.com/docs/houdini/vex/functions/frac.html frac] function, you can cycle through a rainbow over a desired amount of elements.

This is then offset by adding the current time to the fractional value, which produces the scrolling effect.

[[:File:vex_frac_rainbow_cycle_001.hiplc|vex_frac_rainbow_cycle_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb(set(frac(@elemnum/8.0)+@Time/10, 1, 1));
</syntaxhighlight>

== Loop Over All Attributes ==
<syntaxhighlight lang='C'>
string pt_attrs[] = detailintrinsic(1,'pointattributes');
foreach( string pt_attr; pt_attrs ) {
if( pt_attr ~= 'attr_name*' ) {
setpointgroup(0, pt_attr, @ptnum, 1);
}
}
</syntaxhighlight>

== Remove Faces Across Bounding Box ==
<syntaxhighlight lang='C'>
if( relbbox(0,@P).x < rand(@primnum) )
removeprim(0,@primnum,1);
</syntaxhighlight>

== Torus Knot ==
[[File:vex_torus_knot_001.gif | 340px | right]]

[https://prideout.net/knotgl/ Online Knot Viewer]

[[:File:vex_torus_knot_001.hiplc|vex_torus_knot_001.hiplc]]
<syntaxhighlight lang='C'>
float u = float(@ptnum)/(@numpt-1);
u += @Time/10.0;
u %= 1.0;
u *= PI * 2;
float r = 2.0;
float q = 2;
float p = 3;
f@u = u;
@P.x += cos(u*q) * (cos(u*p)+r);
@P.y += sin(u*q) * (cos(u*p)+r);
@P.z += sin(u*p);
</syntaxhighlight>

== Remap Grid to Circle ==

[[File:vex_map_grid_to_circle.gif | 340px | right]]

Working with polar coordinates to map a square onto a circle.

[[:File:vex_map_grid_to_circle.hiplc|vex_map_grid_to_circle.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float theta = @P.x;
float radius = @P.y/2;
@P = 0;
@P.x = sin(theta*PI*2 ) * radius;
@P.y = cos(theta*PI*2 ) * radius;
</syntaxhighlight>

== Remap Grid to Sphere ==

[[File:vex_map_grid_to_sphere.gif | 340px | right]]

Working with polar coordinates to map a square onto a sphere.

[[:File:vex_map_grid_to_sphere.hiplc|vex_map_grid_to_sphere.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float phi = @P.x;
float theta = 1.0-@P.y;
@P.x = sin(theta*PI*1 ) * cos(phi*PI*2 )/2;
@P.z = sin(theta*PI*1 ) * sin(phi*PI*2 )/2;
@P.y = cos(theta*PI*1 )/2;
</syntaxhighlight>

== Make a Quad ==
<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(0,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,1)) );
addvertex(0,prim,addpoint(0,set(0,0,1)) );
</syntaxhighlight>

== Make a Grid ==
<syntaxhighlight lang='C'>
for(int i = 0; i<8; i++) {
for(int j = 0; j<8; j++) {
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(i,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j+1)) );
addvertex(0,prim,addpoint(0,set(i,0,j+1)) );
}
}
</syntaxhighlight>

== Make a Circle ==
[[File:vex_make_circle.gif | 300px | right]]

This example shows how you can generate a circle or N sided polygon using a for loop, sin and cos.

Run the code in detail mode with an attribute wrangle.

This is essentially the same idea as the [https://www.sidefx.com/docs/houdini/nodes/sop/circle.html circle] node but hopefully a beneficial example to see how this type of geometry is generated via VEX.

[[:File:vex_make_circle_001.hiplc|vex_make_circle_001.hiplc]]

<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
int seg = chi('segments');
for( int i = 0; i<seg; i++ ) {
float u = float(i)/seg * 2*PI;
addvertex(0, prim, addpoint(0, set(sin(u),0,cos(u))) );
}
</syntaxhighlight>

== Groups to Attribute ==
[https://zybrand.xyz/groups-to-attribute-with-vex From zybrand]
<syntaxhighlight lang='C'>
//convert numbered groups to a numbered attribute
string groups[] = detailintrinsic(0, "primitivegroups");
int prim = @primnum;
string elemnum;

foreach(string i; groups)
{
//if the current primitive is in group i
if(inprimgroup(0,i,prim) == 1)
{
elemnum = re_find(r"\d{3,6}",i);
}
}
s@number = elemnum;
</syntaxhighlight>

== Looping Curl Noise ==
[[File:2022_12_11_looping_curl_noise.gif | 340px | right]]

It's possible to achieve seamless looping animation from curl noise by blending between two noises.

In this example one noise function is evaluated at the current time, and a second noise function is evaluated at the time shifted back by the desired loop duration.

The result of these two noise functions are blended from one to the other over the duration.

[[:File:vex_looping_noises.hiplc|vex_looping_noises.hiplc]]

<syntaxhighlight lang='C'>
// Position x Frequency
vector p = @P*0.5;
// Speed
float s = 0.5;
// Loop Length (in seconds)
float l = 5;
// Time % duration
float t = (@Time%l);
// Blending
vector v0 = curlgxnoise(p + set(0,0,0,t*s));
vector v1 = curlgxnoise(p + set(0,0,0,(t-l)*s));
@P += lerp(v0,v1,frac(@Time/l)) * 0.35;
</syntaxhighlight>

File:vex rand color from normal direction.hiplc

2024-10-03T10:04:06Z

Admin:

2024-09-01T11:21:53Z

Admin: /* Torus Knot */

== Translate ==
[[File:vex_offset_position.gif | 340px | right]]

Offset the position of geometry

[[:File:vex_offset_position.hiplc|vex_offset_position.hiplc]]
<syntaxhighlight lang='C'>
@P += {1, 0, 0};
</syntaxhighlight>

== Taper ==
[[File:taper_vex_001.gif | 340px | right]]

Reduces the circumference by scaling along the XZ plane based on the height of the geometry.

[[:File:taper_vex_001.hiplc|taper_vex_001.hiplc]]

<syntaxhighlight lang='C'>
float taper = relbbox(0,@P).y;
// Remap the taper range
taper = fit01(taper, 1, fit01(sin(@Time*PI/5)*0.5+0.5, 2.5, .5));
// Apply the taper by scaling along the X and Y axis
@P *= set(taper,1,taper);
</syntaxhighlight>

== Boxify ==
[[File:vex_boxify_001.gif | 340px | right]]

Distorts the geometry, morphing it into a box shape

[[:File:vex_boxify_001.hiplc|vex_boxify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, @P+clamp(normalize(@P)*1.75,vector(-1),vector(1)) * (1.0-length(max(abs(@P)))), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Spherify ==
[[File:vex_spherify_001.gif | 340px | right]]
Distorts the geometry into a sphere shape

[[:File:vex_spherify_001.hiplc|vex_spherify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, normalize(@P), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Stretch ==
[[File:vex_stretch_001.gif | 340px | right]]
Stretch the geometry across it's X axis

Add one component of position to itself to stretch the geometry away from it's center. You can control the amount of stretching by multiplying the position before adding it to itself.

[[:File:vex_stretch_001.hiplc|vex_stretch_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
@P -= centroid;
@P.x += @P.x*chf('amt');
@P += centroid;
</syntaxhighlight>

== Shape Blending ==
[[File:vex_position_blend.gif | 340px | right]]
Blend between point attributes to produce a morph effect

[[:File:vex_position_blend.hiplc|vex_position_blend.hiplc]]
<syntaxhighlight lang='C'>
@P = lerp(@P, @opinput1_P, chf('blend'));
@N = lerp(@N, @opinput1_N, chf('blend'));
</syntaxhighlight>

== Snap to Grid ==

[[File:vex_snap_to_grid.gif | 340px | right]]
Snap ([https://en.wikipedia.org/wiki/Quantization_(signal_processing) quantize]) point positions to a grid for a downres effect

[[:File:vex_snap_to_grid.hiplc|File:vex_snap_to_grid.hiplc]]
<syntaxhighlight lang='C'>
float grid_scale = chf('grid_scale');
@P = rint(@P*grid_scale)/grid_scale;
</syntaxhighlight>

== Make 2D ==
[[File:vex_setcomp.gif | 340px | right]]

You can use the setcomp function to zero out a component of a vector, resulting in a two dimensional surface.

[[:File:vex_setcomp.hiplc|vex_setcomp.hiplc]]
<syntaxhighlight lang='C'>
// Set the X component to zero, planar 2D in YZ
setcomp(@P, 0, 0);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Y component to zero, planar 2D in XZ
setcomp(@P, 0, 1);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Z component to zero, planar 2D in XY
setcomp(@P, 0, 2);
</syntaxhighlight>

== Swizzle Coordinate System ==
[[File:vex_swizzle_vector_components.gif | 340px | right]]

Shuffle the components of a vector using [https://www.sidefx.com/docs/houdini/vex/lang.html#dot-operator swizzle]

[[:File:vex_swizzle_vector_components.hiplc|vex_swizzle_vector_components.hiplc]]
<syntaxhighlight lang='C'>
@P = @P.zyx;
</syntaxhighlight>


== Twirl ==
[[File:vex_twirl.gif | 340px | right]]
Twirl the geometry around the Y axis

[[:File:vex_twirl.hiplc|vex_twirl.hiplc]]

<syntaxhighlight lang='C'>
float a = chf('angle') * length(@P * {1, 0, 1});
float u = atan2(@P.x, @P.z);
float r = length(@P * {1, 0, 1});
@P = set(sin(u-a), @P.y, cos(u-a)) * set(r,1,r);
</syntaxhighlight>



== Peak ==
[[File:vex_push_surface_along_normals.gif | 340px | right]]
Move the surface along it's normals, producing an inflation effect

[[:File:vex_push_surface_along_normals.hip|vex_push_surface_along_normals.hip]]

<syntaxhighlight lang='C'>
@P += normalize(@P) * chf('scale');
</syntaxhighlight>

== Exploded View ==
[[File:vex_exploded_view.gif | 340px | right]]
Moves each packed piece outward from the geometry centroid

[[:File:vex_exploded_view.hiplc|vex_exploded_view.hiplc]]

<syntaxhighlight lang='C'>
@P += (@P - getbbox_center(0)) * chf('scale');
</syntaxhighlight>

== Point Jitter ==
[[File:vex_point_jitter.gif | 340px | right]]
Move each point in a random direction with a spherical distribution

[[:File:vex_point_jitter.hip|vex_point_jitter.hip]]

<syntaxhighlight lang='C'>
@P += sample_sphere_uniform(rand(@elemnum+chf('seed'))) * chf('scale');
</syntaxhighlight>

== Plexus Effect ==
[[File:vex_plexus.gif | 340px | right]]
Connect nearby points

[[:File:vex_plexus.hiplc|vex_plexus.hiplc]]
<syntaxhighlight lang='C'>
foreach(int pt; nearpoints(0, @P, 0.15, 10)) {
if(pt > @ptnum)
addprim(0, 'polyline', @ptnum, pt);
}
</syntaxhighlight>

== Connect to Nearest Point ==
Draw a line to the closest point of the second input
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, vector(point(1,'P',nearpoint(1,@P)))) );
</syntaxhighlight>

== Connect to Closest Surface Position ==
Draw a line to the closest surface position
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, minpos(1,@P) );
</syntaxhighlight>

== Randomize the Rotation of Packed Primitives ==
Update the transform intrinsic to a random orientation
<syntaxhighlight lang='C'>
vector r = sample_direction_uniform(rand(@primnum));
matrix3 x = primintrinsic(0,'transform',i@primnum);
rotate(x, PI*pow(rand(@primnum-666),0.5), r);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Randomize the Scale of Packed Primitives ==
Update the transform intrinsic to a apply a random scale
<syntaxhighlight lang='C'>
vector s = rand(i@primnum);
s = s.yyy; // Uniform Scale
matrix3 x = primintrinsic(0,'transform',i@primnum);
scale(x, s);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Random Color from Normal Direction ==
Generate random colors based on the surface normal, adjust the multiplier to control the amount of colors
<syntaxhighlight lang='C'>
v@Cd = rand(rint(v@N*8));
</syntaxhighlight>

== Iterative Face Insetting ==
Recursive divide and inset edges, [https://twitter.com/d_gfx/status/1452718124579520512 via @d_gfx], excellent use of [https://www.sidefx.com/docs/houdini/vex/arrays.html arrays]
<syntaxhighlight lang='C'>
int pts[] = primpoints(0,@primnum); vector pos[];
int edge_div_pts[]; vector edge_div_pos[];
foreach( int pt; pts )
append(pos, vector(point(0,'P',pt)));
for( int i = 0; i < chi('iterations'); i++ ) {
resize(edge_div_pts,0); // empty
resize(edge_div_pos,0); // empty
for( int j = 0; j < len(pts); j++ ) {
append(edge_div_pos, lerp( pos[j], pos[(j+1)%len(pts)], chf('div_ratio') ));
append(edge_div_pts, addpoint(0, edge_div_pos[-1])); // [-1] grabs the last item from an array
}
for (int k = 0; k < len(pts); k++ ) {
addprim(0, 'poly', pts[k], edge_div_pts[k], edge_div_pts[(k+2)%len(pts)]);
}
pts = edge_div_pts;
pos = edge_div_pos;
}
addprim(0, 'poly', edge_div_pts);
removeprim(0,@primnum,1); // Remove the input prim and any points belonging to it
</syntaxhighlight>

== Iridescent Color Function ==
[[File:vex_iridescent.gif | 340px | right]]

Produce an iridescent color ramp from any varying value, [https://www.shadertoy.com/view/XlcBR7 from shadertoy]

[[:File:vex_iridescent.hiplc|vex_iridescent.hiplc]]

<syntaxhighlight lang='C'>
float amt = dot(@N, set(0,1,0))*0.5+0.5;
v@Cd = (0.5 + 0.5 * cos( PI*2*( amt + set(0,1,2)/3) ) );
</syntaxhighlight>

== Rainbow Colors from HSV Colorspace ==
[[File:vex_hsvtorgb_rainbow_001.gif | 340px | right]]

You can easily control the hue, while keeping the saturation and value the same using the [https://www.sidefx.com/docs/houdini/vex/functions/hsvtorgb.html hsvtorgb] function.

This allows you to easily create rainbows, gradients, perform hue rotations and produce complimentary colors.

[[:File:vex_hsvtorgb_rainbow_001.hiplc|vex_hsvtorgb_rainbow_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb( set(relbbox(0,@P).z - @Time/5 + dot(@N,set(0,1,0))/2, 1, 1));
</syntaxhighlight>

== Rainbow Cycle with frac function ==
[[File:rainbow_cycle_w_frac_VEX.gif | 340px | right]]

Using the [https://www.sidefx.com/docs/houdini/vex/functions/frac.html frac] function, you can cycle through a rainbow over a desired amount of elements.

This is then offset by adding the current time to the fractional value, which produces the scrolling effect.

[[:File:vex_frac_rainbow_cycle_001.hiplc|vex_frac_rainbow_cycle_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb(set(frac(@elemnum/8.0)+@Time/10, 1, 1));
</syntaxhighlight>

== Loop Over All Attributes ==
<syntaxhighlight lang='C'>
string pt_attrs[] = detailintrinsic(1,'pointattributes');
foreach( string pt_attr; pt_attrs ) {
if( pt_attr ~= 'attr_name*' ) {
setpointgroup(0, pt_attr, @ptnum, 1);
}
}
</syntaxhighlight>

== Remove Faces Across Bounding Box ==
<syntaxhighlight lang='C'>
if( relbbox(0,@P).x < rand(@primnum) )
removeprim(0,@primnum,1);
</syntaxhighlight>

== Torus Knot ==
[[File:vex_torus_knot_001.gif | 340px | right]]

[https://prideout.net/knotgl/ Online Knot Viewer]

[[:File:vex_torus_knot_001.hiplc|vex_torus_knot_001.hiplc]]
<syntaxhighlight lang='C'>
float u = float(@ptnum)/(@numpt-1);
u += @Time/10.0;
u %= 1.0;
u *= PI * 2;
float r = 2.0;
float q = 2;
float p = 3;
f@u = u;
@P.x += cos(u*q) * (cos(u*p)+r);
@P.y += sin(u*q) * (cos(u*p)+r);
@P.z += sin(u*p);
</syntaxhighlight>

== Remap Grid to Circle ==

[[File:vex_map_grid_to_circle.gif | 340px | right]]

Working with polar coordinates to map a square onto a circle.

[[:File:vex_map_grid_to_circle.hiplc|vex_map_grid_to_circle.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float theta = @P.x;
float radius = @P.y/2;
@P = 0;
@P.x = sin(theta*PI*2 ) * radius;
@P.y = cos(theta*PI*2 ) * radius;
</syntaxhighlight>

== Remap Grid to Sphere ==

[[File:vex_map_grid_to_sphere.gif | 340px | right]]

Working with polar coordinates to map a square onto a sphere.

[[:File:vex_map_grid_to_sphere.hiplc|vex_map_grid_to_sphere.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float phi = @P.x;
float theta = 1.0-@P.y;
@P.x = sin(theta*PI*1 ) * cos(phi*PI*2 )/2;
@P.z = sin(theta*PI*1 ) * sin(phi*PI*2 )/2;
@P.y = cos(theta*PI*1 )/2;
</syntaxhighlight>

== Make a Quad ==
<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(0,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,1)) );
addvertex(0,prim,addpoint(0,set(0,0,1)) );
</syntaxhighlight>

== Make a Grid ==
<syntaxhighlight lang='C'>
for(int i = 0; i<8; i++) {
for(int j = 0; j<8; j++) {
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(i,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j+1)) );
addvertex(0,prim,addpoint(0,set(i,0,j+1)) );
}
}
</syntaxhighlight>

== Make a Circle ==
[[File:vex_make_circle.gif | 300px | right]]

This example shows how you can generate a circle or N sided polygon using a for loop, sin and cos.

Run the code in detail mode with an attribute wrangle.

This is essentially the same idea as the [https://www.sidefx.com/docs/houdini/nodes/sop/circle.html circle] node but hopefully a beneficial example to see how this type of geometry is generated via VEX.

[[:File:vex_make_circle_001.hiplc|vex_make_circle_001.hiplc]]

<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
int seg = chi('segments');
for( int i = 0; i<seg; i++ ) {
float u = float(i)/seg * 2*PI;
addvertex(0, prim, addpoint(0, set(sin(u),0,cos(u))) );
}
</syntaxhighlight>

== Groups to Attribute ==
[https://zybrand.xyz/groups-to-attribute-with-vex From zybrand]
<syntaxhighlight lang='C'>
//convert numbered groups to a numbered attribute
string groups[] = detailintrinsic(0, "primitivegroups");
int prim = @primnum;
string elemnum;

foreach(string i; groups)
{
//if the current primitive is in group i
if(inprimgroup(0,i,prim) == 1)
{
elemnum = re_find(r"\d{3,6}",i);
}
}
s@number = elemnum;
</syntaxhighlight>

== Looping Curl Noise ==
[[File:2022_12_11_looping_curl_noise.gif | 340px | right]]

It's possible to achieve seamless looping animation from curl noise by blending between two noises.

In this example one noise function is evaluated at the current time, and a second noise function is evaluated at the time shifted back by the desired loop duration.

The result of these two noise functions are blended from one to the other over the duration.

[[:File:vex_looping_noises.hiplc|vex_looping_noises.hiplc]]

<syntaxhighlight lang='C'>
// Position x Frequency
vector p = @P*0.5;
// Speed
float s = 0.5;
// Loop Length (in seconds)
float l = 5;
// Time % duration
float t = (@Time%l);
// Blending
vector v0 = curlgxnoise(p + set(0,0,0,t*s));
vector v1 = curlgxnoise(p + set(0,0,0,(t-l)*s));
@P += lerp(v0,v1,frac(@Time/l)) * 0.35;
</syntaxhighlight>

File:vex torus knot 001.hiplc

2024-09-01T11:20:59Z

Admin:

VEX Wrangle Snippets

2024-09-01T11:12:00Z

Admin: /* Torus Knot */

== Translate ==
[[File:vex_offset_position.gif | 340px | right]]

Offset the position of geometry

[[:File:vex_offset_position.hiplc|vex_offset_position.hiplc]]
<syntaxhighlight lang='C'>
@P += {1, 0, 0};
</syntaxhighlight>

== Taper ==
[[File:taper_vex_001.gif | 340px | right]]

Reduces the circumference by scaling along the XZ plane based on the height of the geometry.

[[:File:taper_vex_001.hiplc|taper_vex_001.hiplc]]

<syntaxhighlight lang='C'>
float taper = relbbox(0,@P).y;
// Remap the taper range
taper = fit01(taper, 1, fit01(sin(@Time*PI/5)*0.5+0.5, 2.5, .5));
// Apply the taper by scaling along the X and Y axis
@P *= set(taper,1,taper);
</syntaxhighlight>

== Boxify ==
[[File:vex_boxify_001.gif | 340px | right]]

Distorts the geometry, morphing it into a box shape

[[:File:vex_boxify_001.hiplc|vex_boxify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, @P+clamp(normalize(@P)*1.75,vector(-1),vector(1)) * (1.0-length(max(abs(@P)))), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Spherify ==
[[File:vex_spherify_001.gif | 340px | right]]
Distorts the geometry into a sphere shape

[[:File:vex_spherify_001.hiplc|vex_spherify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, normalize(@P), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Stretch ==
[[File:vex_stretch_001.gif | 340px | right]]
Stretch the geometry across it's X axis

Add one component of position to itself to stretch the geometry away from it's center. You can control the amount of stretching by multiplying the position before adding it to itself.

[[:File:vex_stretch_001.hiplc|vex_stretch_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
@P -= centroid;
@P.x += @P.x*chf('amt');
@P += centroid;
</syntaxhighlight>

== Shape Blending ==
[[File:vex_position_blend.gif | 340px | right]]
Blend between point attributes to produce a morph effect

[[:File:vex_position_blend.hiplc|vex_position_blend.hiplc]]
<syntaxhighlight lang='C'>
@P = lerp(@P, @opinput1_P, chf('blend'));
@N = lerp(@N, @opinput1_N, chf('blend'));
</syntaxhighlight>

== Snap to Grid ==

[[File:vex_snap_to_grid.gif | 340px | right]]
Snap ([https://en.wikipedia.org/wiki/Quantization_(signal_processing) quantize]) point positions to a grid for a downres effect

[[:File:vex_snap_to_grid.hiplc|File:vex_snap_to_grid.hiplc]]
<syntaxhighlight lang='C'>
float grid_scale = chf('grid_scale');
@P = rint(@P*grid_scale)/grid_scale;
</syntaxhighlight>

== Make 2D ==
[[File:vex_setcomp.gif | 340px | right]]

You can use the setcomp function to zero out a component of a vector, resulting in a two dimensional surface.

[[:File:vex_setcomp.hiplc|vex_setcomp.hiplc]]
<syntaxhighlight lang='C'>
// Set the X component to zero, planar 2D in YZ
setcomp(@P, 0, 0);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Y component to zero, planar 2D in XZ
setcomp(@P, 0, 1);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Z component to zero, planar 2D in XY
setcomp(@P, 0, 2);
</syntaxhighlight>

== Swizzle Coordinate System ==
[[File:vex_swizzle_vector_components.gif | 340px | right]]

Shuffle the components of a vector using [https://www.sidefx.com/docs/houdini/vex/lang.html#dot-operator swizzle]

[[:File:vex_swizzle_vector_components.hiplc|vex_swizzle_vector_components.hiplc]]
<syntaxhighlight lang='C'>
@P = @P.zyx;
</syntaxhighlight>


== Twirl ==
[[File:vex_twirl.gif | 340px | right]]
Twirl the geometry around the Y axis

[[:File:vex_twirl.hiplc|vex_twirl.hiplc]]

<syntaxhighlight lang='C'>
float a = chf('angle') * length(@P * {1, 0, 1});
float u = atan2(@P.x, @P.z);
float r = length(@P * {1, 0, 1});
@P = set(sin(u-a), @P.y, cos(u-a)) * set(r,1,r);
</syntaxhighlight>



== Peak ==
[[File:vex_push_surface_along_normals.gif | 340px | right]]
Move the surface along it's normals, producing an inflation effect

[[:File:vex_push_surface_along_normals.hip|vex_push_surface_along_normals.hip]]

<syntaxhighlight lang='C'>
@P += normalize(@P) * chf('scale');
</syntaxhighlight>

== Exploded View ==
[[File:vex_exploded_view.gif | 340px | right]]
Moves each packed piece outward from the geometry centroid

[[:File:vex_exploded_view.hiplc|vex_exploded_view.hiplc]]

<syntaxhighlight lang='C'>
@P += (@P - getbbox_center(0)) * chf('scale');
</syntaxhighlight>

== Point Jitter ==
[[File:vex_point_jitter.gif | 340px | right]]
Move each point in a random direction with a spherical distribution

[[:File:vex_point_jitter.hip|vex_point_jitter.hip]]

<syntaxhighlight lang='C'>
@P += sample_sphere_uniform(rand(@elemnum+chf('seed'))) * chf('scale');
</syntaxhighlight>

== Plexus Effect ==
[[File:vex_plexus.gif | 340px | right]]
Connect nearby points

[[:File:vex_plexus.hiplc|vex_plexus.hiplc]]
<syntaxhighlight lang='C'>
foreach(int pt; nearpoints(0, @P, 0.15, 10)) {
if(pt > @ptnum)
addprim(0, 'polyline', @ptnum, pt);
}
</syntaxhighlight>

== Connect to Nearest Point ==
Draw a line to the closest point of the second input
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, vector(point(1,'P',nearpoint(1,@P)))) );
</syntaxhighlight>

== Connect to Closest Surface Position ==
Draw a line to the closest surface position
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, minpos(1,@P) );
</syntaxhighlight>

== Randomize the Rotation of Packed Primitives ==
Update the transform intrinsic to a random orientation
<syntaxhighlight lang='C'>
vector r = sample_direction_uniform(rand(@primnum));
matrix3 x = primintrinsic(0,'transform',i@primnum);
rotate(x, PI*pow(rand(@primnum-666),0.5), r);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Randomize the Scale of Packed Primitives ==
Update the transform intrinsic to a apply a random scale
<syntaxhighlight lang='C'>
vector s = rand(i@primnum);
s = s.yyy; // Uniform Scale
matrix3 x = primintrinsic(0,'transform',i@primnum);
scale(x, s);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Random Color from Normal Direction ==
Generate random colors based on the surface normal, adjust the multiplier to control the amount of colors
<syntaxhighlight lang='C'>
v@Cd = rand(rint(v@N*8));
</syntaxhighlight>

== Iterative Face Insetting ==
Recursive divide and inset edges, [https://twitter.com/d_gfx/status/1452718124579520512 via @d_gfx], excellent use of [https://www.sidefx.com/docs/houdini/vex/arrays.html arrays]
<syntaxhighlight lang='C'>
int pts[] = primpoints(0,@primnum); vector pos[];
int edge_div_pts[]; vector edge_div_pos[];
foreach( int pt; pts )
append(pos, vector(point(0,'P',pt)));
for( int i = 0; i < chi('iterations'); i++ ) {
resize(edge_div_pts,0); // empty
resize(edge_div_pos,0); // empty
for( int j = 0; j < len(pts); j++ ) {
append(edge_div_pos, lerp( pos[j], pos[(j+1)%len(pts)], chf('div_ratio') ));
append(edge_div_pts, addpoint(0, edge_div_pos[-1])); // [-1] grabs the last item from an array
}
for (int k = 0; k < len(pts); k++ ) {
addprim(0, 'poly', pts[k], edge_div_pts[k], edge_div_pts[(k+2)%len(pts)]);
}
pts = edge_div_pts;
pos = edge_div_pos;
}
addprim(0, 'poly', edge_div_pts);
removeprim(0,@primnum,1); // Remove the input prim and any points belonging to it
</syntaxhighlight>

== Iridescent Color Function ==
[[File:vex_iridescent.gif | 340px | right]]

Produce an iridescent color ramp from any varying value, [https://www.shadertoy.com/view/XlcBR7 from shadertoy]

[[:File:vex_iridescent.hiplc|vex_iridescent.hiplc]]

<syntaxhighlight lang='C'>
float amt = dot(@N, set(0,1,0))*0.5+0.5;
v@Cd = (0.5 + 0.5 * cos( PI*2*( amt + set(0,1,2)/3) ) );
</syntaxhighlight>

== Rainbow Colors from HSV Colorspace ==
[[File:vex_hsvtorgb_rainbow_001.gif | 340px | right]]

You can easily control the hue, while keeping the saturation and value the same using the [https://www.sidefx.com/docs/houdini/vex/functions/hsvtorgb.html hsvtorgb] function.

This allows you to easily create rainbows, gradients, perform hue rotations and produce complimentary colors.

[[:File:vex_hsvtorgb_rainbow_001.hiplc|vex_hsvtorgb_rainbow_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb( set(relbbox(0,@P).z - @Time/5 + dot(@N,set(0,1,0))/2, 1, 1));
</syntaxhighlight>

== Rainbow Cycle with frac function ==
[[File:rainbow_cycle_w_frac_VEX.gif | 340px | right]]

Using the [https://www.sidefx.com/docs/houdini/vex/functions/frac.html frac] function, you can cycle through a rainbow over a desired amount of elements.

This is then offset by adding the current time to the fractional value, which produces the scrolling effect.

[[:File:vex_frac_rainbow_cycle_001.hiplc|vex_frac_rainbow_cycle_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb(set(frac(@elemnum/8.0)+@Time/10, 1, 1));
</syntaxhighlight>

== Loop Over All Attributes ==
<syntaxhighlight lang='C'>
string pt_attrs[] = detailintrinsic(1,'pointattributes');
foreach( string pt_attr; pt_attrs ) {
if( pt_attr ~= 'attr_name*' ) {
setpointgroup(0, pt_attr, @ptnum, 1);
}
}
</syntaxhighlight>

== Remove Faces Across Bounding Box ==
<syntaxhighlight lang='C'>
if( relbbox(0,@P).x < rand(@primnum) )
removeprim(0,@primnum,1);
</syntaxhighlight>

== Torus Knot ==
[[File:vex_torus_knot_001.gif | 340px | right]]

[https://prideout.net/knotgl/ Online Knot Viewer]

<syntaxhighlight lang='C'>
float u = float(@ptnum)/(@numpt-1);
u += @Time/10.0;
u %= 1.0;
u *= PI * 2;
float r = 2.0;
float q = 2;
float p = 3;
f@u = u;
@P.x += cos(u*q) * (cos(u*p)+r);
@P.y += sin(u*q) * (cos(u*p)+r);
@P.z += sin(u*p);
</syntaxhighlight>

== Remap Grid to Circle ==

[[File:vex_map_grid_to_circle.gif | 340px | right]]

Working with polar coordinates to map a square onto a circle.

[[:File:vex_map_grid_to_circle.hiplc|vex_map_grid_to_circle.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float theta = @P.x;
float radius = @P.y/2;
@P = 0;
@P.x = sin(theta*PI*2 ) * radius;
@P.y = cos(theta*PI*2 ) * radius;
</syntaxhighlight>

== Remap Grid to Sphere ==

[[File:vex_map_grid_to_sphere.gif | 340px | right]]

Working with polar coordinates to map a square onto a sphere.

[[:File:vex_map_grid_to_sphere.hiplc|vex_map_grid_to_sphere.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float phi = @P.x;
float theta = 1.0-@P.y;
@P.x = sin(theta*PI*1 ) * cos(phi*PI*2 )/2;
@P.z = sin(theta*PI*1 ) * sin(phi*PI*2 )/2;
@P.y = cos(theta*PI*1 )/2;
</syntaxhighlight>

== Make a Quad ==
<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(0,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,1)) );
addvertex(0,prim,addpoint(0,set(0,0,1)) );
</syntaxhighlight>

== Make a Grid ==
<syntaxhighlight lang='C'>
for(int i = 0; i<8; i++) {
for(int j = 0; j<8; j++) {
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(i,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j+1)) );
addvertex(0,prim,addpoint(0,set(i,0,j+1)) );
}
}
</syntaxhighlight>

== Make a Circle ==
[[File:vex_make_circle.gif | 300px | right]]

This example shows how you can generate a circle or N sided polygon using a for loop, sin and cos.

Run the code in detail mode with an attribute wrangle.

This is essentially the same idea as the [https://www.sidefx.com/docs/houdini/nodes/sop/circle.html circle] node but hopefully a beneficial example to see how this type of geometry is generated via VEX.

[[:File:vex_make_circle_001.hiplc|vex_make_circle_001.hiplc]]

<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
int seg = chi('segments');
for( int i = 0; i<seg; i++ ) {
float u = float(i)/seg * 2*PI;
addvertex(0, prim, addpoint(0, set(sin(u),0,cos(u))) );
}
</syntaxhighlight>

== Groups to Attribute ==
[https://zybrand.xyz/groups-to-attribute-with-vex From zybrand]
<syntaxhighlight lang='C'>
//convert numbered groups to a numbered attribute
string groups[] = detailintrinsic(0, "primitivegroups");
int prim = @primnum;
string elemnum;

foreach(string i; groups)
{
//if the current primitive is in group i
if(inprimgroup(0,i,prim) == 1)
{
elemnum = re_find(r"\d{3,6}",i);
}
}
s@number = elemnum;
</syntaxhighlight>

== Looping Curl Noise ==
[[File:2022_12_11_looping_curl_noise.gif | 340px | right]]

It's possible to achieve seamless looping animation from curl noise by blending between two noises.

In this example one noise function is evaluated at the current time, and a second noise function is evaluated at the time shifted back by the desired loop duration.

The result of these two noise functions are blended from one to the other over the duration.

[[:File:vex_looping_noises.hiplc|vex_looping_noises.hiplc]]

<syntaxhighlight lang='C'>
// Position x Frequency
vector p = @P*0.5;
// Speed
float s = 0.5;
// Loop Length (in seconds)
float l = 5;
// Time % duration
float t = (@Time%l);
// Blending
vector v0 = curlgxnoise(p + set(0,0,0,t*s));
vector v1 = curlgxnoise(p + set(0,0,0,(t-l)*s));
@P += lerp(v0,v1,frac(@Time/l)) * 0.35;
</syntaxhighlight>

VEX Wrangle Snippets

2024-09-01T11:11:40Z

Admin: /* Torus Knot */

== Translate ==
[[File:vex_offset_position.gif | 340px | right]]

Offset the position of geometry

[[:File:vex_offset_position.hiplc|vex_offset_position.hiplc]]
<syntaxhighlight lang='C'>
@P += {1, 0, 0};
</syntaxhighlight>

== Taper ==
[[File:taper_vex_001.gif | 340px | right]]

Reduces the circumference by scaling along the XZ plane based on the height of the geometry.

[[:File:taper_vex_001.hiplc|taper_vex_001.hiplc]]

<syntaxhighlight lang='C'>
float taper = relbbox(0,@P).y;
// Remap the taper range
taper = fit01(taper, 1, fit01(sin(@Time*PI/5)*0.5+0.5, 2.5, .5));
// Apply the taper by scaling along the X and Y axis
@P *= set(taper,1,taper);
</syntaxhighlight>

== Boxify ==
[[File:vex_boxify_001.gif | 340px | right]]

Distorts the geometry, morphing it into a box shape

[[:File:vex_boxify_001.hiplc|vex_boxify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, @P+clamp(normalize(@P)*1.75,vector(-1),vector(1)) * (1.0-length(max(abs(@P)))), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Spherify ==
[[File:vex_spherify_001.gif | 340px | right]]
Distorts the geometry into a sphere shape

[[:File:vex_spherify_001.hiplc|vex_spherify_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
vector size = getbbox_size(0);
size = min(size); // Largest component
@P -= centroid;
@P *= (1.0/size);
@P = lerp(@P, normalize(@P), chf('blend'));
@P *= size;
@P += centroid;
</syntaxhighlight>

== Stretch ==
[[File:vex_stretch_001.gif | 340px | right]]
Stretch the geometry across it's X axis

Add one component of position to itself to stretch the geometry away from it's center. You can control the amount of stretching by multiplying the position before adding it to itself.

[[:File:vex_stretch_001.hiplc|vex_stretch_001.hiplc]]
<syntaxhighlight lang='C'>
vector centroid = getbbox_center(0);
@P -= centroid;
@P.x += @P.x*chf('amt');
@P += centroid;
</syntaxhighlight>

== Shape Blending ==
[[File:vex_position_blend.gif | 340px | right]]
Blend between point attributes to produce a morph effect

[[:File:vex_position_blend.hiplc|vex_position_blend.hiplc]]
<syntaxhighlight lang='C'>
@P = lerp(@P, @opinput1_P, chf('blend'));
@N = lerp(@N, @opinput1_N, chf('blend'));
</syntaxhighlight>

== Snap to Grid ==

[[File:vex_snap_to_grid.gif | 340px | right]]
Snap ([https://en.wikipedia.org/wiki/Quantization_(signal_processing) quantize]) point positions to a grid for a downres effect

[[:File:vex_snap_to_grid.hiplc|File:vex_snap_to_grid.hiplc]]
<syntaxhighlight lang='C'>
float grid_scale = chf('grid_scale');
@P = rint(@P*grid_scale)/grid_scale;
</syntaxhighlight>

== Make 2D ==
[[File:vex_setcomp.gif | 340px | right]]

You can use the setcomp function to zero out a component of a vector, resulting in a two dimensional surface.

[[:File:vex_setcomp.hiplc|vex_setcomp.hiplc]]
<syntaxhighlight lang='C'>
// Set the X component to zero, planar 2D in YZ
setcomp(@P, 0, 0);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Y component to zero, planar 2D in XZ
setcomp(@P, 0, 1);
</syntaxhighlight>
<syntaxhighlight lang='C'>
// Set the Z component to zero, planar 2D in XY
setcomp(@P, 0, 2);
</syntaxhighlight>

== Swizzle Coordinate System ==
[[File:vex_swizzle_vector_components.gif | 340px | right]]

Shuffle the components of a vector using [https://www.sidefx.com/docs/houdini/vex/lang.html#dot-operator swizzle]

[[:File:vex_swizzle_vector_components.hiplc|vex_swizzle_vector_components.hiplc]]
<syntaxhighlight lang='C'>
@P = @P.zyx;
</syntaxhighlight>


== Twirl ==
[[File:vex_twirl.gif | 340px | right]]
Twirl the geometry around the Y axis

[[:File:vex_twirl.hiplc|vex_twirl.hiplc]]

<syntaxhighlight lang='C'>
float a = chf('angle') * length(@P * {1, 0, 1});
float u = atan2(@P.x, @P.z);
float r = length(@P * {1, 0, 1});
@P = set(sin(u-a), @P.y, cos(u-a)) * set(r,1,r);
</syntaxhighlight>



== Peak ==
[[File:vex_push_surface_along_normals.gif | 340px | right]]
Move the surface along it's normals, producing an inflation effect

[[:File:vex_push_surface_along_normals.hip|vex_push_surface_along_normals.hip]]

<syntaxhighlight lang='C'>
@P += normalize(@P) * chf('scale');
</syntaxhighlight>

== Exploded View ==
[[File:vex_exploded_view.gif | 340px | right]]
Moves each packed piece outward from the geometry centroid

[[:File:vex_exploded_view.hiplc|vex_exploded_view.hiplc]]

<syntaxhighlight lang='C'>
@P += (@P - getbbox_center(0)) * chf('scale');
</syntaxhighlight>

== Point Jitter ==
[[File:vex_point_jitter.gif | 340px | right]]
Move each point in a random direction with a spherical distribution

[[:File:vex_point_jitter.hip|vex_point_jitter.hip]]

<syntaxhighlight lang='C'>
@P += sample_sphere_uniform(rand(@elemnum+chf('seed'))) * chf('scale');
</syntaxhighlight>

== Plexus Effect ==
[[File:vex_plexus.gif | 340px | right]]
Connect nearby points

[[:File:vex_plexus.hiplc|vex_plexus.hiplc]]
<syntaxhighlight lang='C'>
foreach(int pt; nearpoints(0, @P, 0.15, 10)) {
if(pt > @ptnum)
addprim(0, 'polyline', @ptnum, pt);
}
</syntaxhighlight>

== Connect to Nearest Point ==
Draw a line to the closest point of the second input
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, vector(point(1,'P',nearpoint(1,@P)))) );
</syntaxhighlight>

== Connect to Closest Surface Position ==
Draw a line to the closest surface position
<syntaxhighlight lang='C'>
addprim(0, 'polyline', @ptnum, addpoint(0, minpos(1,@P) );
</syntaxhighlight>

== Randomize the Rotation of Packed Primitives ==
Update the transform intrinsic to a random orientation
<syntaxhighlight lang='C'>
vector r = sample_direction_uniform(rand(@primnum));
matrix3 x = primintrinsic(0,'transform',i@primnum);
rotate(x, PI*pow(rand(@primnum-666),0.5), r);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Randomize the Scale of Packed Primitives ==
Update the transform intrinsic to a apply a random scale
<syntaxhighlight lang='C'>
vector s = rand(i@primnum);
s = s.yyy; // Uniform Scale
matrix3 x = primintrinsic(0,'transform',i@primnum);
scale(x, s);
setprimintrinsic(0,'transform',i@primnum,x);
</syntaxhighlight>

== Random Color from Normal Direction ==
Generate random colors based on the surface normal, adjust the multiplier to control the amount of colors
<syntaxhighlight lang='C'>
v@Cd = rand(rint(v@N*8));
</syntaxhighlight>

== Iterative Face Insetting ==
Recursive divide and inset edges, [https://twitter.com/d_gfx/status/1452718124579520512 via @d_gfx], excellent use of [https://www.sidefx.com/docs/houdini/vex/arrays.html arrays]
<syntaxhighlight lang='C'>
int pts[] = primpoints(0,@primnum); vector pos[];
int edge_div_pts[]; vector edge_div_pos[];
foreach( int pt; pts )
append(pos, vector(point(0,'P',pt)));
for( int i = 0; i < chi('iterations'); i++ ) {
resize(edge_div_pts,0); // empty
resize(edge_div_pos,0); // empty
for( int j = 0; j < len(pts); j++ ) {
append(edge_div_pos, lerp( pos[j], pos[(j+1)%len(pts)], chf('div_ratio') ));
append(edge_div_pts, addpoint(0, edge_div_pos[-1])); // [-1] grabs the last item from an array
}
for (int k = 0; k < len(pts); k++ ) {
addprim(0, 'poly', pts[k], edge_div_pts[k], edge_div_pts[(k+2)%len(pts)]);
}
pts = edge_div_pts;
pos = edge_div_pos;
}
addprim(0, 'poly', edge_div_pts);
removeprim(0,@primnum,1); // Remove the input prim and any points belonging to it
</syntaxhighlight>

== Iridescent Color Function ==
[[File:vex_iridescent.gif | 340px | right]]

Produce an iridescent color ramp from any varying value, [https://www.shadertoy.com/view/XlcBR7 from shadertoy]

[[:File:vex_iridescent.hiplc|vex_iridescent.hiplc]]

<syntaxhighlight lang='C'>
float amt = dot(@N, set(0,1,0))*0.5+0.5;
v@Cd = (0.5 + 0.5 * cos( PI*2*( amt + set(0,1,2)/3) ) );
</syntaxhighlight>

== Rainbow Colors from HSV Colorspace ==
[[File:vex_hsvtorgb_rainbow_001.gif | 340px | right]]

You can easily control the hue, while keeping the saturation and value the same using the [https://www.sidefx.com/docs/houdini/vex/functions/hsvtorgb.html hsvtorgb] function.

This allows you to easily create rainbows, gradients, perform hue rotations and produce complimentary colors.

[[:File:vex_hsvtorgb_rainbow_001.hiplc|vex_hsvtorgb_rainbow_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb( set(relbbox(0,@P).z - @Time/5 + dot(@N,set(0,1,0))/2, 1, 1));
</syntaxhighlight>

== Rainbow Cycle with frac function ==
[[File:rainbow_cycle_w_frac_VEX.gif | 340px | right]]

Using the [https://www.sidefx.com/docs/houdini/vex/functions/frac.html frac] function, you can cycle through a rainbow over a desired amount of elements.

This is then offset by adding the current time to the fractional value, which produces the scrolling effect.

[[:File:vex_frac_rainbow_cycle_001.hiplc|vex_frac_rainbow_cycle_001.hiplc]]

<syntaxhighlight lang='C'>
v@Cd = hsvtorgb(set(frac(@elemnum/8.0)+@Time/10, 1, 1));
</syntaxhighlight>

== Loop Over All Attributes ==
<syntaxhighlight lang='C'>
string pt_attrs[] = detailintrinsic(1,'pointattributes');
foreach( string pt_attr; pt_attrs ) {
if( pt_attr ~= 'attr_name*' ) {
setpointgroup(0, pt_attr, @ptnum, 1);
}
}
</syntaxhighlight>

== Remove Faces Across Bounding Box ==
<syntaxhighlight lang='C'>
if( relbbox(0,@P).x < rand(@primnum) )
removeprim(0,@primnum,1);
</syntaxhighlight>

== Torus Knot ==
[[File:vex_torus_knot_001.gif | 340px | right]]

[https://prideout.net/knotgl/ Online Knot Viewer]
<syntaxhighlight lang='C'>
float u = float(@ptnum)/(@numpt-1);
u += @Time/10.0;
u %= 1.0;
u *= PI * 2;
float r = 2.0;
float q = 2;
float p = 3;
f@u = u;
@P.x += cos(u*q) * (cos(u*p)+r);
@P.y += sin(u*q) * (cos(u*p)+r);
@P.z += sin(u*p);
</syntaxhighlight>

== Remap Grid to Circle ==

[[File:vex_map_grid_to_circle.gif | 340px | right]]

Working with polar coordinates to map a square onto a circle.

[[:File:vex_map_grid_to_circle.hiplc|vex_map_grid_to_circle.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float theta = @P.x;
float radius = @P.y/2;
@P = 0;
@P.x = sin(theta*PI*2 ) * radius;
@P.y = cos(theta*PI*2 ) * radius;
</syntaxhighlight>

== Remap Grid to Sphere ==

[[File:vex_map_grid_to_sphere.gif | 340px | right]]

Working with polar coordinates to map a square onto a sphere.

[[:File:vex_map_grid_to_sphere.hiplc|vex_map_grid_to_sphere.hiplc]]
<syntaxhighlight lang='C'>
@P += {0.5, 0.5, 0}; // Remap the grid to zero to one range
float phi = @P.x;
float theta = 1.0-@P.y;
@P.x = sin(theta*PI*1 ) * cos(phi*PI*2 )/2;
@P.z = sin(theta*PI*1 ) * sin(phi*PI*2 )/2;
@P.y = cos(theta*PI*1 )/2;
</syntaxhighlight>

== Make a Quad ==
<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(0,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,0)) );
addvertex(0,prim,addpoint(0,set(1,0,1)) );
addvertex(0,prim,addpoint(0,set(0,0,1)) );
</syntaxhighlight>

== Make a Grid ==
<syntaxhighlight lang='C'>
for(int i = 0; i<8; i++) {
for(int j = 0; j<8; j++) {
int prim = addprim(0,'poly');
addvertex(0,prim,addpoint(0,set(i,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j)) );
addvertex(0,prim,addpoint(0,set(i+1,0,j+1)) );
addvertex(0,prim,addpoint(0,set(i,0,j+1)) );
}
}
</syntaxhighlight>

== Make a Circle ==
[[File:vex_make_circle.gif | 300px | right]]

This example shows how you can generate a circle or N sided polygon using a for loop, sin and cos.

Run the code in detail mode with an attribute wrangle.

This is essentially the same idea as the [https://www.sidefx.com/docs/houdini/nodes/sop/circle.html circle] node but hopefully a beneficial example to see how this type of geometry is generated via VEX.

[[:File:vex_make_circle_001.hiplc|vex_make_circle_001.hiplc]]

<syntaxhighlight lang='C'>
int prim = addprim(0,'poly');
int seg = chi('segments');
for( int i = 0; i<seg; i++ ) {
float u = float(i)/seg * 2*PI;
addvertex(0, prim, addpoint(0, set(sin(u),0,cos(u))) );
}
</syntaxhighlight>

== Groups to Attribute ==
[https://zybrand.xyz/groups-to-attribute-with-vex From zybrand]
<syntaxhighlight lang='C'>
//convert numbered groups to a numbered attribute
string groups[] = detailintrinsic(0, "primitivegroups");
int prim = @primnum;
string elemnum;

foreach(string i; groups)
{
//if the current primitive is in group i
if(inprimgroup(0,i,prim) == 1)
{
elemnum = re_find(r"\d{3,6}",i);
}
}
s@number = elemnum;
</syntaxhighlight>

== Looping Curl Noise ==
[[File:2022_12_11_looping_curl_noise.gif | 340px | right]]

It's possible to achieve seamless looping animation from curl noise by blending between two noises.

In this example one noise function is evaluated at the current time, and a second noise function is evaluated at the time shifted back by the desired loop duration.

The result of these two noise functions are blended from one to the other over the duration.

[[:File:vex_looping_noises.hiplc|vex_looping_noises.hiplc]]

<syntaxhighlight lang='C'>
// Position x Frequency
vector p = @P*0.5;
// Speed
float s = 0.5;
// Loop Length (in seconds)
float l = 5;
// Time % duration
float t = (@Time%l);
// Blending
vector v0 = curlgxnoise(p + set(0,0,0,t*s));
vector v1 = curlgxnoise(p + set(0,0,0,(t-l)*s));
@P += lerp(v0,v1,frac(@Time/l)) * 0.35;
</syntaxhighlight>

File:vex torus knot 001.gif

2024-09-01T11:10:51Z

Admin:

Houdini USD Cookbook

2024-08-09T19:40:21Z

Admin:

[https://www.sidefx.com/docs/houdini//solaris/pattern.html Primitive matching patterns]

[https://www.sidefx.com/docs/houdini//solaris/vex.html Using VEX with USD]

[https://www.sidefx.com/docs/houdini/nodes/lop/karmastandardrendervars.html Karma Standard Render Vars]

[https://renderman.pixar.com/resources/RenderMan_20/risLPEs.html LPEs]

2024-07-30T17:54:54Z

Admin:

Some useful resources to help you with Houdini.

''' Geometry '''

[http://threedscans.com/ Three D Scans] | [https://3d.si.edu/cc0 Smithsonian] | [https://wirewheelsclub.com/models/ Wire Wheels Club] | [http://www.graphics.stanford.edu/data/3Dscanrep/ Stanford 3D Scans] | [https://sketchfab.com/blogs/community/sketchfab-launches-public-domain-dedication-for-3d-cultural-heritage/ Sketchfab 3D Cultural Heritage] | [https://www.myminifactory.com/scantheworld/full-collection My Mini Factory] | [http://casual-effects.com/data/index.html Casual-Effects Data] | [http://www.sampleandhold.co.uk/downloads/ Sample and Hold] | [https://benedikt-bitterli.me/resources/ Benedikt-Bitterli.me] | [https://jangafx.com/software/embergen/download/free-vdb-animations/ EmberGen VDBs]
----
''' HDRIs '''

[https://hdrihaven.com/hdris/ Poly Haven] | [http://themarichannel.com/all-hdr/ The Mari Channel] | [https://renderman.pixar.com/category/111-hdri Renderman] | [http://noemotionhdrs.net/ No Emotion HDRs] | [http://www.hdrlabs.com/sibl/archive.html HDR Labs SIBL]
----
''' Textures '''

[https://ambientcg.com/categories ambientCG] | [https://3dtextures.me/ 3D Textures] | [https://www.cgbookcase.com/textures CG Bookcase] | [https://texturebox.com/ Texture Box] | [http://thepatternlibrary.com/ The Pattern Library] | [https://www.textures.com/ Textures.com] | [http://texturify.com/ Texturify] | [http://uvchecker.byvalle.com/ UV Grid Generator] | [https://physicallybased.info/ Physically Based Shader Values]
----
''' Tools '''

[https://color.adobe.com/explore Adobe Color] | [https://www.iquilezles.org/apps/graphtoy/ Graphtoy] | [https://fonts.google.com/ Google Fonts] | [https://www.canva.com/colors/color-palettes/ Canva Color Palettes] | [https://www.canva.com/colors/color-palettes/ Hex Color Palettes] | [https://windmillart.net/?p=jsplacement Jsplacement] | [https://rainboxlab.org/tools/dume/ Dume] | [https://soulwire.co.uk/math-for-motion/ Math for Motion] | [http://foxcodex.html.xdomain.jp/index.html Periodic Table of Motion] | [https://mrviewer.sourceforge.io/ mrViewer] | [https://carbon.now.sh/ Carbon] | [https://github.com/anvaka/city-roads City Roads] | [https://pureref.com PureRef] | [https://redketchup.io/twitter-downloader Save mp4 and gif from Twitter] | [https://wumbo.net/glossary/ Math Glossary] | [https://ezgif.com/ EZgif Convert]
----
''' Inspiration '''

[https://motionographer.com/tag/photoreal/ Motionographer Photoreal] | [https://www.stashmedia.tv/ Stash Magazine] | [http://artofstyleframe.com/ Art of Style Frame] | [https://www.artofthetitle.com/ Art of the Title] | [https://www.behance.net/galleries/motion/ Behance Motion Gallery] | [https://www.behance.net/search/projects/?search=Houdini%20FX Behance Houdini FX] | [https://www.sakugabooru.com/tag?name=&type=&order=count Sakuga Booru] | [http://ref-fx.com/ FX References] | [https://www.instagram.com/explore/tags/xuxoe/ Instagram #xuxoe] | [https://beforesandafters.com/ Before & Afters] | [https://butdoesitfloat.com/img/random But Does It Float] | [https://fyfluiddynamics.com/ FYFD] | [https://dribbble.com/tags/houdini Houdini Dribble] | [https://www.are.na/john-kunz are.na] | [http://foxcodex.html.xdomain.jp/index.html Motion Periodic Table] | [http://www.sylvain-nouveau.com/reffx/misc/ FX References] | [https://mr5ivethou5and.tumblr.com/archive mr5ivethou5and] | [https://timeline.lerandom.art/ Generative Art Timeline] | [https://www.youtube.com/playlist?list=PLyzOQqMHGyYTsz7-jlj-SeOm6iC0v-7B3 5 Decades of digital art history on YouTube]
----
''' Houdini '''

[https://www.houdinikitchen.net/2019/12/21/how-to-create-l-systems/ L Systems] | [https://procegen.konstantinmagnus.de/ procegen] | [https://hdbp.io/browse Houdini Blueprints] | [https://github.com/kiryha/Houdini/wiki/vex-for-artists VEX Guide for Artists] | [https://www.sidefx.com/contentlibrary/ SideFX Content Library] | [https://forums.odforce.net/topic/49522-tutorial-hip-library/ OdForce Tutorial .hip Library] | [https://www.sidefx.com/learn/getting_started/ SideFX Getting Started] | [https://forums.odforce.net/topic/24056-learning-vex-via-animated-gifs-bees-bombs/ OdForce Learning VEX Via Bees and Bombs] | [https://houdinigubbins.wordpress.com/ Houdini Gubbins] | [http://wordpress.discretization.de/houdini/ Houdini Tech Blog] | [https://www.sidefx.com/houdini-hive/houdini-hive-worldwide/ Hive] | [https://www.tokeru.com/cgwiki/index.php?title=Houdini Tokeru] | [https://ikrima.dev/houdini/basics/hou-crash-course/ Crash Course] | [https://jeremypaton.github.io/site/build/nodes/sop.html SOP Quick Reference] | [https://discord.gg/dbJrmM8 Kunz Discord Community] | [https://houdiniquicktips.weebly.com/ Quick Tips]