Ptex Displacement from Mudbox

[tylerART]

Howdy all,

I've read a bunch of posts here about rendering ptex files from Mudbox, but I haven't seen anyone running into the problem I'm having. I'm doing a test to see how feasible ptex is for production, and I'm running into a subdivision and displacement issue. I've sculpted my head in Mudbox and I've exported the color textures as ptex all fine. They all render correctly out of Maya. I then go and create my displacement map. I'm doing a standard displacement from Mudbox. Everything renders out fine, then I run into a snag. As you can see from my image below, the displacement map isn't displacing correctly. I'm getting 3 problems, although they all could be stemming from a single issue.



First off, my displacement isn't accurately moving the mesh into the correct position. Secondly, I'm getting regions of faceting, most visible on the back of the head in the rim light. Thirdly, there seem to be seams of smooth and faced areas, like around the bridge of the nose.

I'm not doing any displacement shift, and I've left all my displacement amount's to 1. It's a 32bit float ptex. My Mudbox settings are:
Method: subdivision
Texel Distribution: Use Ptex Setup

Anyone know how to fix this?

Brent Tyler

[vlado]

What were the settings in Mudbox when you exported the Ptex displacement file?

Best regards,
Vlado

[Zach Gray]

I had early issues with ptex/mudbox.

The problem was from how you prepare the mesh in mudbox. You have to smooth model to final res BEFORE you setup ptex/paint.

I can't quite tell if that's your issue or not. Also, did you enable 'use negative colors' on the vrayPtex?

[tylerART]

Thanks for your answers guys. I do recall sculpting at higher resolutions before I setup Ptex. I'll do a test in a minute to see if that solves my issues.

Vlado, here are my settings.

[tylerART]

Here's a simple test I did with a 10x10 plane and I get the same problem. You can see the seam areas along with some strange faceting.



By the way, I'm using Maya 2013.5 with the latest stable build of VRay as of 2/2/13.

[vlado]

Use a different filter for the PTex texture; the Box filter will get you such artifacts. See here: http://www.spot3d.com/vray/help/200R...tex.htm#render

A bit further down the page I show the difference between Box and Cubic filters.

Best regards,
Vlado

[tylerART]

I've tried all sorts of filtering, from box to gaussian, to bicubic and I still get the same result. When I started, I upped the mudbox ptex definition to roughly 8k before I started painting, so I don't imagine the displacement faceting is pixelization. Even if it was, doesn't VRay displace subdivisions along a smoothed normal?

Have you tried a simple test scene? Are you getting the same result?

[vlado]

Works fine for me... if you like, you can send us the .mud file with the issue to vraymaya@chaosgroup.com and we'll try to figure out what's wrong.

Best regards,
Vlado

[FSGFX]

I had early issues with ptex/mudbox.

The problem was from how you prepare the mesh in mudbox. You have to smooth model to final res BEFORE you setup ptex/paint.

I can't quite tell if that's your issue or not. Also, did you enable 'use negative colors' on the vrayPtex?

i cant find the "allow negative colors" in the ptex node... is there something hidden.?

http://docs.chaosgroup.com/display/VRAY3MAYA/VRayPtex

[FSGFX]

update:

im only able to get good results with uvs and vector displacement... ptex is missing all the negative values...

[Zach Gray]

Try this mel:

vray addAttributesFromGroup VRayPtex1 vray_file_allow_neg_colors 1;

where VRayPtex1 is the name of your ptex node.

[FSGFX]

thanks Zach buts its looking the same... i can see the attribute on the node but no affect...

[Svetlozar Draganov]

Would it be possible to send us Maya and Mudbox scene for investigation?

[FSGFX]

im on vacation, but i will send something in your direction next week.

[FSGFX]

Hi Draganov i contacted the support to setup a ftp or something to send the file to you.
its to big for an email.