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Gumball Machine

Software used - Houdini, Mantra

This is an expression animation project from my Houdini class. All the cubes and spheres were driven by an audio clip by using CHOP. Everything was made in Houdini 18.0.287 and rendered in Mantra.


Import a piano soundtrack file and adjust the audio clip. Parametric EQ is to filter the audio wave from 1000 to 160. The Envelope channel node outputs the absolute maximum amplitude of each sample of the input and I use the Math channel node to convert the audio wave from range 0–1 to range 0.35–1.6.

Use Attribute Wrangle node to read the wave data from chop and use it to control the size and position Y of cubes. All the cubes will transform with the audio wave.


I use RBD to make all the cubes collide with each other. The POP Attract dynamics node applies a force to steer all the cubes towards the center position instead of keeping popping outwards. After all the settings are done, cache the geometry file.

In order to let the color change along with audio wave like size and position, I set a ramp and use Attribute Wrangle node to read the ramp. I have tried rough glass, classic shader and plastic shader to create the one like my reference but failed. Finally ends up with basic liquid, which gives me more room to play with


Responsible for all aspects.

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