Ptex Normal Displacement workflow

[hellobard]

Hey guys,

I have hunted through every thread about ptex normal displacement on the forum and I can't find any information on how to make it work like a normal UV'd displacement would. I suspect this may have something to do with the troubles you're having with the vector displacement and subdivisions of the geometry, but I vlado said that normal displacement with Ptex's worked fine in one of the posts.

Here's the original level 7 sculpt in Mudbox:


Level 0 obj imported to Maya and Ptex level 7 displacement map applied with no subdivision/smoothing:


Smoothed with 2 subdivisions:


V-Ray subdivided by 7 subdivs:


Extra Vray Attributes for the object:


The ptex file node has a cache of 400mb and I've tried both box filtering and no filtering. Both produce the same results.

What am I doing wrong / Is it possible?

Edit:
Maybe Level 0 was a bit much to handle to go all the way to level 7... I'm pulling out my n00b card on this one! But still, it would be nice to know what the correct workflow to make ptex normal displacement work.

[VasilVelikov]

I don't see anything wrong with the settings. Can you send me your Maya scene and Ptex file to vasil.velikov@chaosgroup.com ? The Mudbox file will also be useful.

[Reaversword]

I'm trying to do the same as you Hellobard, while with uvs & exr works perfect, still any lucky for my side.

Neither with Displacements nor with Vector Displacements.

I too have researched the forum, tested all options in many combinations, nothing...

[hellobard]

I sent my files to Vasil yesterday, so hopefully he can have a look at it and determine what's wrong with my workflow

As you can see from my picture, V-Ray obviously reads the ptex displacement file, I think it's just a matter of getting it to subdivide the mesh according to the values of the ptex map. Something seems fishy in that area anyway...

[Reaversword]

Hellobard, yesterday I get ptex displacement perfectly working, with Vray 2.0 not nightly, under Win 7 x64.

Just apply a Vray Mtl material, in the shading group, add ptex in the displacement slot, turn off filtering. Usually the "default" mesh configuration is "normal displacement", activate it if you prefer in the Vray extra attributes of the mesh.

In my case, the trouble was in that Vray doesn't was reading the ptex, so I forced to it linking the texture as bump map and leaving the bump to 0. This way I get Vray reads the ptex, but avoid any bump.


Hellobard, did you remember to use the "ptex" mesh (bring the mesh from Mudbox)?, maybe its a silly mistake!. In Maya ptex meshes appears to have various maps together, take a look at Uv Editor.

Hope you get it working soon!, and then, we can try to get Vector Displacement working... the max I've reached has been take it working in the part where geometry raises from the original, negative displacement not works, neither with "allow negative colors" option working.

[hellobard]

That's interesting that you got it working!
I did essentially exactly the same. Tried it with two different tests/meshes.

Did you add any subdividing on your mesh or did it work without it?

[Reaversword]

Without it. Did it works for you?

[hellobard]

Nope, tried it again, exporting the base mesh and the ptex once more, but to no avail. Still the exact same result :/ Maybe this is an issue with the nightlies?

[DPGrafik]

I have experienced a ptex error with the nightlies. It is essentially broken at the moment. However if you revert to the latest stable version ptex works just fine. But then you loose the Vray Framebuffer, which does not work with the stable version. At least not the one i have installed now. It's 1-2 weeks since i last updated.

In regards to getting vector displacement working with ptex- you won't get it to work. I've asked Vlado about it, and it has something to do with the way vector displacement work and the way ptex work. it is, as far as i understand, not yet implemented in the file format to work. Vector disp, needs UV's to know where to displace apparently. but that may all change very soon - who knows

[vlado]

Yes, there seems to be some problem there, we are looking into it...

Best regards,
Vlado

[VasilVelikov]

Thank you for the scene, hellobard.
I've tested it with the latest nightly(the one from revision 16905) and I managed to render your scene succesfully. Here's what I did. At first, I tried to use the ptex file that you sent me. And I got exactly the same results as yours. I don't know why, maybe the file was incorrect. That's why I used the Mudbox scene you've sent me to export a new displacement map. By the way, how do you export your displacement map? Here is my method: in Mudbox, select Maps->Extract Texture Maps->New Operation. Select "Displacement Map". Set the quality to Good/High, select "32 bit float" for the Data Format and click Extract.
The next thing you should do is adjust your texture bounds. The values of the displacement map are arbitrary i.e. they aren't between 0 and 1. However, the ptex node in Maya is supposed to return a color and thus the result is assumed to be in the [0, 1] interval. Displacement values that are outside this interval are clamped. In order to get it working you should set the "Displacement bounds" to Explicit and adjust them yourself. First, click on the "Min value" color(the black rectangle). The H, S, V values should be 0. Set the V value to, say, -5. Now encrease the "Max value" to 15. Now try to render it. You may need to expand the min/max interval, there is no way to say how big it should be(of course, you can always set it to [-100, 100]).

DPGrafik - what error are you talking about?

[hellobard]

Thank you for the help, Vasil! It now works perfectly!

As I mentioned in my email to you, it would be great to have a Displacement type preset for ptex displacement, both for ease of use and for saving time.

Very excited about ptex displacement working, it is going to be great fun to drop UVs almost entirely from my workflow.