Stephen Cooney


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Houdini Skills


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Recent Forum Posts

Pyro, Voxels & Particles, Time based effects. Oct. 24, 2009, 5:52 p.m.

There are no particles in voxel fluids, the voxels are simply recording vector and scalar values as they pass through.

Forgive me because I'm new to Houdini and don't quite understand it's inner workings, but I believe a common way voxel based fluid fields work is by containing hidden particles. Yes, the scalar values mark how dense each voxel is but I thought that this was achieved by putting dummy particles into the fluid and moving this along and then sampling them later in each voxel for density.

If not then that's rough. Does anybody have a link to a technical description (programmer's description) of how the Houdini voxel fluids are implemented?

One thing we want to do (or consider doing) is causing the fluid in the voxel cloud to disappear based on how long it's been alive. Any suggestions?

Another thing we were considering is spawning a simulated object (like a leaf or a flower) when a particular part of the fluid has been alive long enough. Any suggestions?

Pyro, Voxels & Particles, Time based effects. Oct. 22, 2009, 2:08 p.m.

Is there a way to get access to the sub-particles in the pyro voxel based fluid simulator?

Basically we need to do time-based effects on the fluid. One idea is that after a particle in the fluid has been alive for a certain time it is destroyed and another is that we might want to freeze the particles after a certain time, creating a hardening effect.

Any ideas?

Particle Velocities, Inherit Velocity, Hack Velocity, Help! Oct. 5, 2009, 7:04 p.m.

Hello everyone, first post and all but I need some help for a problem.

Obviously inherit velocity for particles takes whatever object they're attached to and uses that velocity for the particles. This is what we want. However, since keyframed objects do not have a velocity this will not work for characters or hand animated objects.

Is there a way to get Houdini to look at the change in the object over time to automatically calculate velocity? Furthermore, can this be done for surface points so that an animated skeleton would emit particles with various velocities (ex: standing still but waving an arm)?

(what I'm imagining right now is a script that compares this frame with the last frame and spawning particles based off of the differences. I don't quite have the time available to learn the houdini library to implement it in python though)

Thanks for your help! ops: