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Friday, July 19, 2013

(just another) Houdini FLIP water sim







Houdini fountain water sim - FLIP solver test from Alessandro Pepe on Vimeo.

A few days ago I realized the world couldn't survive without my contribution to the countless water simulation tests out there. Honestly this is not better or worse than many others but I had so much fun working on it.
I spent about 5 days overall between setup and render.

The workflow is pretty much the same explained in the SideFX Waterfall tutorials, with some minor changes in the water shader, and the creation of a wet map. Furthermore I paid extra attention to the bubbles underwater.

For the wet map I used Attribute Transfer SOP to transfer the "wetness" attribute from the particles generated by the Flip Simulation (after caching only the ones close to the fountain walls) to a dense particle object scattered on the fountain. The attribute transferring was performed in a DOPs Network (via SOP Solver), in order to preserve the previous state.

Initially I created 2 different wet maps:
  • WETNESS - This is a wet map that dries very quickly and reveals only the water spec on the fountain shader.
  • DARKNESS - This wet map is identical to the previous one for what concerns the shape, but dries way way slower and is in charge of keeping the fountain shader just darker.
Eventually I ended up using only the "DARKNESS" wetmap cause the light position didn't show any wet part of the fountain revealed by the water, (unfortunately) so ... useless ! But I thought it was a good idea to illustrate both wetness (in cyan) and darkness (in blue), in the pass below.


Houdini Wet map from Alessandro Pepe on Vimeo.

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