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barbapapa
02-06-2007, 08:46 PM
Hi people, i have a shot where i have a duck coming out of water, any way, the duck has to leave some foot prints on the ground (water footprints) and is gonna be a camera matching shot. Does any one knows if there is a way to set up a shader for this situation.?? creating an animated map is going to be really hard, since the duck is going to be dancing salsa :argh: . I guess the best thing to do would be to create a shader that identifies the geometry or something... but i just dont know how to set up this.... any advice would be much appreciated.
Thanks in advanced :)

mdee
02-06-2007, 10:20 PM
Hi people, i have a shot where i have a duck coming out of water, any way, the duck has to leave some foot prints on the ground (water footprints) and is gonna be a camera matching shot. Does any one knows if there is a way to set up a shader for this situation.?? creating an animated map is going to be really hard, since the duck is going to be dancing salsa :argh: . I guess the best thing to do would be to create a shader that identifies the geometry or something... but i just dont know how to set up this.... any advice would be much appreciated.
Thanks in advanced :)

Can you separate or add dummy flat foot geometry to your rig, assign white constant shader to it, make it black when foot is above the ground, assign black constant shader to your background (only contact surface)?

If yes, render it from the top ortho camera after animation is done and use as alpha channel mask.

If contact surface is something more complex than almost planar grid then I don't have any solutions at this time of the day ;).

pooby
02-07-2007, 09:05 AM
I'd experiment with the FX tree and link up effects (for dispersion and/or drying up after contact with the ground) to a clip.
Also, if you use texture supports, using the animated clip, you can constrain them to the feet, and 'drop them off' to the ground when the foot lands.

Per-Anders
02-07-2007, 09:22 AM
There are a few methods of doing this (I'm talking generally here, not related to XSI in specific), here's just a small selection...

1) The first is to know exactly where the feet are going ot be and literally paint them in in time and render that to an animation that you then use in conjunction with your duck animation, this is simple, but time consuming and a bugger if the client makes changes. The typical method is to actually render orthagonal from below and you do the rest in after effects.

2) The second is similar but this time you actually animate in individually projected footbprints visibility combining in a multiply situation (that's then inverted, though you can use add the toruble is it'll end up brighter than white).

3) The next option is again related, but this time what you do is the orthagonal render form below and you have a black plane and make the creature 100% white, then have the plane slightly higher than the groundplane and remove all other geometry, now you'll be able to render out an animation where the feet are coming through the surface, this is great because you can then use frame echoes in after effects (or wherever) to retain the footprints over time and let them fade out for a nice wet footprints effect (i may even do a small tutorial to cover this sometime), then of course you just reproject the result back up into your scene onto the floot, you may want to add some small particle effects and blurring of course to enhance the effect.

4) You can use a particle based setup, using either particles themselves for the shading, or having a shader that uses the proximity of the particles to it's surface to shade. Certain applications have such shaders inbuilt, with XSI this might be more of a problem as there's not much relationship between teh scene and the shader tree withotu scripting/coding.

Anyhow hopefully those will give you some ideas.

With regards the wet stuff itself, you just want a darkening layer that you'll sue in post using basically a low opacity multiply and a bit of overlay, and then a reflection pass, that'll probably be enough for the basic look. Good luck!

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02-07-2007, 09:22 AM
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