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anamous

water dress stuff

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We just came off a project where we put a water dress on a model. Our TD Daniel Stern developed a particle fluid force for maya particles, and we (thanks, Stefan Habel) brought these particles into Houdini where we meshed, deformed, and abused them, and rendered them using micropoly PBR.

http://www.youtube.com/watch?v=PXmsVW8JxhM&fmt=18

If anyone finds himself in the same position, drop me a note :lol:

cheers,

Abdelkareem

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really nice work...

I wouldn't mind seeing the clean plate.... :)

it would be cool to see more clips of the different stages of this...

thanks for posting it!

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Thanks for the kind words everyone.

The water shader is a simple glass shader, with the IOR set to 1/1.3 of course (or even less if it looked better in a shot). This is one example where micropoly PBR is actually way quicker than normal PBR. Since glass (not having a diffuse or glossy component) clears up already at low PBR sampling levels, and we needed motion blur, we could ramp up the pixel samples while keeping the raytrace variance to somewhere around 9 to 16 samples. If this was a clay surface it would have been grainy beyond recognition, but since it's glass, we could get away with it. The reason for PBR is that the speed hit for specular bounces (AKA reflection/refraction limit) is minimal. We had it up to 100 and had rendertimes of about 2 to 4 minutes per PAL frame.

The particle fluid surface SOP is a force to be reckoned with, it's truly awesome. We created an SDF representation of the model which we could subtract from the fluid volume, keeping intersections to a minimum. Plus, we meshed the fluid a bit thicker, and flattened it with a VOP SOP that did the job of the ray SOP but in a multithreaded manner - sometimes spending a few hours writing a "redundant" VOP SOP can really pay off. Since the particle streams came in separate blocks (body, dress, splashes), we had to combine them in houdini, and fit the dress using a magnet SOP to the rest of the moving body.

cheers,

Abdelkareem

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Very nice work!

But, you used Real Flow?

Why?

Mark

Hi xionmark. Yes, we used Realflow for some splashes. We basically threw virtual water onto the model and then filtered the parts of the splashes that looked good on the maya/houdini water dress. This was done to add some ambience and an element of chaos, and also to give the compositing guys some material to work from in case the director wanted more water in a shot, so that shot didn't have to be re-sent through the whole pipeline. The Realflow elements are secondary but add important visual cues. Realflow was used because we have two capable operators - Houdini particle fluids were an option, but our Houdini pipeline was already locked up for the main dress.

cheers,

Abdelkareem

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Good quality version here (with weird quality voice over).

http://motionographer.com/wp-content/uploa...i_star_h264.mov

Thanks for the info.

So, were the particles animated to a moving model or to a static model, then deformed in houdini to match the moving girl?

The top part of the dress and the lower part were simulated separately onto the matchmoved girl (the basic mechanism being an inhouse developed simple SPH interaction plugin for Maya particles and a series of force fields that either kept the particles close to the body or made them flow into the form of the dress), and didn't have a flow between them. So we took the particle passes and used the magnet SOP and other deformers to stitch them together and to keep the lower part pinned to the model's hip.

cheers,

Abdelkareem

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The particle fluid surface SOP is a force to be reckoned with, it's truly awesome. We created an SDF representation of the model which we could subtract from the fluid volume, keeping intersections to a minimum. Plus, we meshed the fluid a bit thicker, and flattened it with a VOP SOP that did the job of the ray SOP but in a multithreaded manner - sometimes spending a few hours writing a "redundant" VOP SOP can really pay off. Since the particle streams came in separate blocks (body, dress, splashes), we had to combine them in houdini, and fit the dress using a magnet SOP to the rest of the moving body.

cheers,

Abdelkareem

Hi anamous,

Great work! I wish I have more time to play with PBR more.

When you flattened the fluid, do you mean flattening it against the model? Or just making it thinner? I'm working on some water stuff and would like to know what you did there.

Thanks for sharing!

Cheers!

steven

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