Baking motion vectors to UV space....

[MartinB]

Hi there,

We're trying to make a shader that blends in displacement or texture changes to parts of a model that are in motion (ie static body but moving arms)

The only way I can think would be a two part render. The first pass would be very quick and just bake the motion vectors to each objects UV space. These images could then be post processed to make a black and white mask, black = no motion, white = motion. Then that could be fed into a shader network for the main render and used to drive the texture/disp changes in the area's that have motion.

We had something working quite nicely written in RSL but am struggling to get a similar effect with vray.

Any help of pointers would be greatly appreciated. I'd prefer to not have to go down the cpp shader writing route.

Cheers
Martin

[vlado]

Do you need the velocity in world space, object space or screen space (or you just need the speed - i.e. the velocity magnitude)? What we can do relatively quickly is add a "velocity" or "speed" output to the additional V-Ray attributes for the samplerInfo node.

Best regards,
Vlado

[MartinB]

For what we're trying to achieve I think a velocity magnitude in object space would be ideal.... We wouldn't want camera or world transforms to affect it.

Thanks Vlado, I wasn't expecting such a direct response from the developers! On another note, I've had a read of a few threads on here and was wondering if there was any news on implementing metaSL or the custom shader language hinted at?

Cheers
Martin

[MartinB]

Hi Vlado,

I was wondering what sort of time frame it would be to get something like the velocity implemented on the sample info node? We've got the motion vectors baking to UV space working but it'd be nice to have that data running straight out the sample info node without doing the prepass/bake.

Another area we're looking into is making a 'stretch map' showing which area's of a mesh are expanding or contracting. At the minute we're going down the route of writing a plug-in to go through the animation comparing face sizes between frames and passing that information to the mesh's vertex colour, then using those in a shading network. Again it'd be nice to have something in the sample info node that could achieve this....

I'm just starting to look into metaSL so will probably be on to you for access to the Maya version soon, just abit busy with other things at the minute

cheers
Martin

[MartinB]

<BUMP>

Any news on the above Vlado?

Also is there a bug/feature request database we can look at to see if problems we are running into or features we want are already in there.

Cheers
Martin