shave & haircut 8 (and 7) bug - connections not being made and not rendering hair

[thebeals]

This seems to be a tricky question and I don't even know if there is a solution.. We've generally rendered hair with MR using puppet tk mats, but I am trying to get us to use Vray so everything is in one renderer and there are significant texturing issues with shave 7 and above. However, I am coming across an incredible bug that I cannot figure out and would appreciate your help bebugging. Mods, if this is not the right forum, please move it to the appropriate one.

I have tried this is Maya 2013 and 2014 with shave 7 and 8 and similar things happen in both. I am rendering using Vray 2.30.01.

If I have multiple hair systems and hide one, and render, then the one hidden is hidden and everything is fine. If I unhide that hairsytem and render so it is visible, it still is hidden and does not render and will never render again, even if I close maya (even without saving the updated scene) and re-open, that system will not render. I have also found that when increasing a light's intensity, it will cause certain hair systems to disappear. In Maya 2014, there is no error reported, however is 2013, when changing the light's intensity and render, I get this error:

// Error: line 1: Connection not made: 'pSolidShape3.instObjGroups[0]' -> 'VRayMtlHair31SG.dagSetMembers[5]'. Destination attribute must be writable. //

So it seems that the temp mesh (psolid3) that gets created at render time for the hair, is unable to write to the SG... Maybe? But I can't figure out why because it is created at render time disappears once the render finishes. However, when I put that material on a simple sphere, the sphere renders fine, so it seems to be a shave-specific issue. Mental Ray does not seem to have any of these issues (which is surprising with how unstable it generally is with these things).

I have attached a Maya 2013 .MA scene to illustrate the problem using shave 8. ShaveHair2 and 3 will not render for me even though they are set to be visible.

I really would appreciate any and all help. This is the first project I am trying Vray on in hopes to get the rest of my studio on board and I could totally use a win with this one since the look is far superior than MR (imho).

sphere_testing.zip

Any ideas or work arounds? I am almost positive this has to be a shave issue, but the folks here are some of the brightest, so if anyone can figure it out, it's you guys.

[sharktacos]

We switched over to using Maya hair, so I have not done much with Shave in a while. However I do recall seeing the first issue of the hair suddenly not rendering. In those cases the two culprits we ran into a lot were (1) the post render mel for shave disappearing (in which case you can manually type it in again) and (2) the render type needing to be switched from prims to geo in the shave globals. Hope that helps a little.

[thebeals]

Thanks for the response, I'll take a look into it. Are you using nhair? We've been looking at using nhair actually, but the character we are needing to do has hundreds of thousands of hairs. From my understanding, you have your follicle with a clump of hairs that grows out of it. It seems like I would need thousands of thousands of follicles to be able to get a groom that would look good (and match the look of the shave and haircut version) without having to rely on clumps. Has this been your experience? Is it slow?

I've also found that using nhair, the texturing is all messed up, so you have to do a lot of funny uv and scaling to get the geo and uvs matching so 1 to 1 so you can get textures working. Is this the same on your end, or are you using something other than nhair?

Thanks for the thoughts!

[Morbid Angel]

Some times such issue can occur when the pre render mel is not executed. So the fur is not passed to vray.

[thebeals]

What are the pre and post render scripts that should be run?

[sharktacos]

Are you using nhair? We've been looking at using nhair actually, but the character we are needing to do has hundreds of thousands of hairs. From my understanding, you have your follicle with a clump of hairs that grows out of it. It seems like I would need thousands of thousands of follicles to be able to get a groom that would look good (and match the look of the shave and haircut version) without having to rely on clumps. Has this been your experience? Is it slow?

Yes we are using a combination of Vray fur with vector maps for short fur and hair, and nHair for groomed longer hair. With nHair you can have a clumpy look, but you can also instead spread out the interpolation more evenly. In that case the clumps in nHair are more like the guide curves in Shave. I have not done speed comparisons, but I would think this would be dependent on Vray, rather than whether the hair is made with Shave or nHair

Frankly the grooming with nHair is a pain (basically the curves need to be generated manually) and it requires a lot of complex setup to get the nHair to behave with the curves properly. So I have high hopes for xGen and am eagerly awaiting it's implementation in the next version of Vray! If you are outside of the U.S. you might want to look into Yeti. I wish we could use it here!

[Morbid Angel]

What are the pre and post render scripts that should be run?

when you use shave, it automatically places two scripts ShavePreRenderMel and ShavePostRenderMel (though my actual naming might be off) those are required for fur to be properly passed to vray. Look at any scene example from shave. If you do not have those, the fur will not render.

[thebeals]

The prim to geo worked! Thanks for the help!

[shadevfx]

Hi thebeals,

I've found a solution to this problem! After banging my head through my monitor all day I found a simple workaround that at this point seems to solve the problem. If you select your defualt lambert shader 'lambert1' then select the 'initial shading group' and navigate to the attribute editor you can apply a 'V-Ray material override' to the initial shading group via the 'Attributes' pulldown at the top of the attribute editor.

After doing so you will have an 'Extra V-Ray Attributes' tab from which you can 'Enable V-Ray Material Override'. Here I simply placed my V-Ray hair shader into the 'V-Ray Material' slot and unchecked everything else (GI Material Override, Reflection Material Override, Refraction Material Override, etc.)

After doing this all of your shave nodes should work correctly. From what I understand adding the override to the initial shading group forces the psolid temp meshes that are created at render time to render with the (initial shading group) which is now being replaced by the V-Ray Material Override which means all fur should behave properly when activated or unactivated.

Secondly the only other thing I've noticed is that the 'shavedisplay' shape names seem to all have the same shape name. Because this happens by default when making new hair systems I manually change the 'shavedisplay' shape name after I create new ones, that way there is no confusion at render time.

I really hope this helps.

Cheers,

Eric

[thebeals]

Awesome, shadevfx!! You are the best!