Cant get accurate displacement from VRay Maya. (Files & Image Examples included)

[RockinAkin]

Hey there!

I cant get accurate displacement working in maya for the life of me...
I've been using a test I developed that worked fine in 3ds Max & VRay.

Take a look at the attached image to see what I mean.
You can download the test file and displacement map here: http://www.cggallery.com/temp/test_disp.zip

[Zach Gray]

Freeze scale transforms before you send it to mudbux.

The displacement map is being generated from the pre-transform geometry. If you don't want to re-generate your map, then apply the inverse scale to your displacement.

I've seen this several times, perhaps it's your issue.

[RockinAkin]

The planes in the maya scene have never been scaled - their scale transforms are all at 1... so I don't believe this to be the problem unless I'm missing something here.

(Maya and Mudbox's units are set to CM)

[Zach Gray]

I made my own in mudbox, exported rgb exr. Works perfectly.

Loaded yours in nuke, confirmed pixel values 5 and -15, but was only in the r channel. I think vray is taking the sum of the rgb exr values for the displacement. I shuffled the r into the gb channels and your file works fine.

I was thinking you could just set the scalar 'Displacement Ammount' to 3 to compensate for the zero values in gb, but that doesn't seem to have any effect on either exr. I've been using ptx files for the past year, and that scalar seems to work there and with procedural textures, so I'm not sure what the deal is. Easy fix is to export rgb exr's from mudbox.

My guess is that it reads disp this way in order to properly support vector displacement.

(On an unrelated note... saw you did WDFA talent dev program. When did you do that? Knew a couple animators in the program last summer.)

[RockinAkin]

Oh man - that was it! Not having anything in the G/B channels was the culprit... resulting in 1/3 the expected displacement strength!

Thanks a lot Zach - I owe you a beer.