Strange normal maps with Mental Ray

mbrzezicki

Hopefully someone can help me with an issue that's been bugging me for a while now. When using Mental Ray to render out my games models, I've noticed that normal maps which had displayed exactly as I wanted them in the Maya viewport will be different, often dramatically so - harshly warped and not as expected.

I'm having to render them like this as a way to work around the transparency errors that Maya apparently has with my NVIDIA graphics card.

These screen grabs should show you what I mean. Maya viewport view on the left, Mental Ray render on the right. They're both using the exact same light setup but the render seems to be taking on the light in a different way...



Help!

mbrzezicki

Turns out Mental Ray just doesn't render normal maps very well. Nothing that can really be done about it.

r_fletch_r

MR renders normal maps pretty well for me in max. Id say maya and mental ray are not using the rendering method for their normal maps. have you tried flipping the green channel?



Why are you using a scanline renderer to render your game assets, surely a viewport shader, unreal, or marmoset model viewer would be much better and more realistic ways to present a game model

Racer445

This is because your tangent basis isn't synced. If you are going to display in mental ray you should also bake with metal ray. http://wiki.polycount.com/NormalMap#Tangent_Basis

chronic

Render Settings > Mental Ray > Options (tab) > Maya Derivatives

mbrzezicki

chronic wrote: »

Render Settings > Mental Ray > Options (tab) > Maya Derivatives

Thanks, chronic. That fixed it right up.

And thanks everyone for your help. The question was initially posted some months back and I've since put that model to bed but it'll be useful to know this in the future.