vray hair shader?

[sharktacos]

Could someone give a basic walk-through of how to use the vray hair shader?
Is it available in the regular 2.0 install?
If so how do we access it? Is it a plugin or something?

Sort of in the dark here, so any pointers would be appreciated

Also, can you render render element multi-mattes with it? This was something you could not do with Shave's native shader because you could not assign an objectID or materialID to it. So I'm hoping to be able to assign the vray shader to the shave hair to get this...

[Zdravko]

VRayHairMtl shader is designed for rendering hair and fur. It's available only in the latest V-Ray 2.20 for Maya build.
To assignee it, you need to select the hair and add extra attributes in the Attribute editor : Attributes>VRay>Hair Shader
Then you can set VRayMtlHair3 in the Extra VRay Attributes roll-out.

To extract the hair in separate channel you can use Material Select render element.

[sharktacos]

Thanks for the info! This works for Maya hair. How would one use this with Maya fur?

[treyharrell]

A question on this... I've been able to apply Hair3 to both VRay fur and Maya Hair, but I can't seem to get it to pick up UV information from a hair system, regardless of whether the surface is UV linked to the hair system, or whether the follicles have appropriate surface UV params.

Is there a trick to get this to work?

Thanks,

--T

[griml0ck]

You can use the hairSampleInfo node. But this technique is a bit flawed currently. I haven't found a way to UV map the transparency while also being able to map the hair transparency along the hair strand with maya hair for example. But it works to get the hair color from the maya hair node.

[sharktacos]

Can someone go over how to use the vrayHairSampler together with the vrayMtlHair3 (assuming this is how you get the hair shader to work with texture maps)? I have managed to get the vrayMtlHair3 to render out with Shave, but I cannot get it to read any of the texture maps for the hair color which makes the whole thing pretty unusable ATM. Simply putting a texture map into the diffuse color on the vrayMtlHair3 (which would normally work for other hair shaders) seems to ignore any UV info on the connected geo (so a red and white checker map becomes solid pink). Any help appreciated!

[griml0ck]

I think that node is designed to work with maya hair to be able to texture it with the vrayhair shader. With shave I have no clue. I would recommend using yeti if you want a good groomer that has a good intergration with vray and maya.

[sharktacos]

Could someone from Chaos comment on this please? Does the new vray hair really not work with texture maps in Shave?

[bigbossfr]

I have some questions :
1) I have a surface (head), i want that the hair have the color of the head color (get the "surface color"). It is possible ? If yes, how ?
2) I want the root to be black, and the tip to be white. I know i must to use the "vray hair sampler" node and a black and white ramp. But now, i want to have the color of the head in the black color of the ramp. It is possible ?

Thank you.

[vlado]

Could someone from Chaos comment on this please? Does the new vray hair really not work with texture maps in Shave?

Unfortunately it doesn't. I have it on the "to do" list to go through the Shave shaders and let Joe Alter know what needs to be changed to support it. Shave's native shader should work fine though.

Best regards,
Vlado

[sharktacos]

Okay, thanks for the info.

The trouble with the native shave shader is that
1) it does not work with multi-mattes since you can't assign an object or material ID to it.
2) it does not do a degamma on the swatches when "linear" is checked in the color mapping rollout.

Both of these of course work with vrayHairMtl3, so I was hoping to use it together with Shave. Oh well, something to look forward to I guess...

[treyharrell]

Actually, it's possible to add a pre-frame MEL command just after the shavePreRender script which adds an object ID to the piece of placeholder geo that's inserted into the scene at rendertime.

Haven't got a cut of Shave with me at the moment... but run the pre-frame script from your globals and you'll see the geo name. From there it's possible to iterate similarly named objects and auto-create multimattes depending on how many shaveNodes are in your scene. Just add your own preframe MEL after Joe's.

--T

[sharktacos]

If you could share the MEL for that it would be awesome. I'm not very good at that kind of thing so I don't think I could write it myself.

[griml0ck]

I have some questions :
1) I have a surface (head), i want that the hair have the color of the head color (get the "surface color"). It is possible ? If yes, how ?
2) I want the root to be black, and the tip to be white. I know i must to use the "vray hair sampler" node and a black and white ramp. But now, i want to have the color of the head in the black color of the ramp. It is possible ?

Thank you.

If your using MayaHair you can use the "Vray hair sampler" node. Connect a texture to your maya hair and connect the hair color from the hair sampler node to diffuse on the vray hair shader for example. I haven't found the need to use the black roots and white tips since vray does that for you in the shading if your using GI and the vray hair shader 3. But if you still feel the need to make the roots blacker I guess you could use the fur sampler node and connect that to a ramp and then connect that to the reflection slots of the hair shader to make the hair darker in the roots. I have not found a way to do a combination of the two, unless vlado has a workaround for that?

Vray fur can already pick up a texture. And yeti hair can also be textured. I don't know what shave can do, we don't use that here. We tried it and it just had too many limitations that we decided not to use it.

[bigbossfr]

I tried to setup the hair to pick up the texture color of the head, i failed.
If anyone or Vlado know how i can do this, it will be great !

To have a ramp on your hair, connect a VrayHairSampler (distanceAlongStrand) to the V of a ramp, and connect your ramp where you want into the VrayHairMtl (color for example). You will have black and white root/tip.