kunz Live 2022.09.16

Live 2022.09.16

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Iridescent Bismuth

content thumbnail 2022 09 16.jpg


Bismuth Crystals are a really interesting area to study. The hopper crystal forms and iridescent colors are very nice to look at and create an almost alien or psychedelic feeling.

Similar phenomenons can be observed in metallurgy, patterns in nature, and some animals in nature.

Stream Summary

The Standard Surface model implemented in Karma and MaterialX has a thin film model for metallic reflections, which can create these rainbow-like iridescence effects.

I wanted to try out the thin film model and initially test it on a shaderball to get a sense of how the settings and parameters work.

After experimenting with the shader, I procedurally model a simple maze-like geometric form using the path finding node in Houdini. This form is then instanced to a point cloud to create the repetitive fractal-like form, similar to Bismuth crystals.

Below is the final render with some animation applied to the geometry as well as the lights ⤵

2022 09 16 mtlx metal spin.gif

Karma viewport example tumbling around the scene ⤵

2022 09 16 viewport karma.gif


I also suggest taking a look at Bruno Militelli's Bismuth photographs

You can also find some 3d models of Bismuth on Sketchfab which can be downloaded and imported into Houdini to test shaders on.

Modeling with Find Shortest Path

2022 09 16 find shortes path examples.gif

The Find Shortest Path node can be used not only for finding the shortest path between two points, but can be used to create complex, interesting path networks.

This file contains the example animation above, and shows a few different ways the node can be used: 2022_09_16_find_shortest_path_examples.hiplc

Video On Demand

  • 0:00:00 introduction
  • 0:01:00 MaterialX shaderball
  • 0:04:50 creating MaterialX shader
  • 0:05:40 adding a dome light
  • 0:08:40 loading a .mtlx example shader
  • 0:10:00 graphing the .mtlx shader
  • 0:12:40 examine the .mtlx file text
  • 0:21:00 adjusting thin film thickness and for
  • 0:32:30 using noise to drive thin film
  • 0:37:00 using facing ratio to drive thin film
  • 0:40:00 procedural modeling in SOPs
  • 0:41:00 find shortest path
  • 0:48:00 sweeping a custom font profile
  • 0:53:40 applying our shader
  • 0:58:00 duplicating and instancing
  • 0:59:00 adding camera and area lights
  • 1:04:40 extending the instancing workflow
  • 1:06:50 sphere packing with vdbtospheres SOP
  • 1:15:00 rendering
  • 1:20:00 adjusting lights for better highlights
  • 1:28:00 adding depth of field
  • 1:44:00 adding physical lens shader
  • 1:56:00 final render
  • 1:59:00 wrapping up

Scene File