Maya 2015 mirrored normal map seam in mental ray?

Tzur_H

I don't want to steal the thread or anything but a friend of mine at school got a very similar issue so thought I might ask here.

Here's what we did: Using Maya 2015
Modeled half, UVed, mirrored across, mirrored UVs moved exactly 1 unit on U, set UV splits to hard edges - everything else to soft, baked world space normal using Xnormal with compute binormals in pixel shader on, map converted to tangent using handplane - seam visible when rendering using mental ray, but looks perfectly fine in viewport 2.0.

Any clues?

Eric Chadwick

This was in the thread Problem with mirrored normal map.

But yours is using different software. So this a different issue, and belongs in its own thread.

I suspect that the mental ray renderer isn't proper synced to Maya's baker (nor to Handplane). It works fine in viewpot 2.0, so that means it is indeed using the right tangent space. It's just mental ray's fault then.

Eric Chadwick

What happens if you bake a tangent map in Maya, and don't do any processing, but just try to render it with mental ray, applied to the low-poly model?

Tzur_H

So...I did a bit of research around the internet and found a way to fix it, might be useful to someone else with this issue. Might also want to add to the Wiki?

In mental ray render settings go to Options > Performance > Make sure 'Export Polygon Derivatives' AND 'Maya Derivatives' are ticked ON.

Here's a comparison render without and with these settings:




* Working in Maya 2015 - Deleted half, mirrored across, moved mirrored UVs 1 unit out of 0,1 space, set UV border to hard edges, triangulated before export.
Baked using Xnormal in World Space, converted using Handplane to Tangent with Maya 2013/2014 preset.