Problem with Normal Maps (VRay)

[Anonymous]

I am not sure where I am going wrong in setting up the normals, but I am getting this "dark" effect when the bump value exceeds around 30%.

The leaves in this example are using a VRay2Sided material with normal maps generated in Knald. The normal maps are going through a VRayNormalMap node. Any advice as to what might be causing this would be appreciated!

In terms of the normal map setup, should the normals be imported as a regular bitmap, or VRayHDRI (sRGB/Inverse Gamma)? In the VRayNormalMap, do any channels need to be flipped? I have tried several different permutations but I am not sure what the right combination is.

Setup:

VRayHDRI/Bitmap -> VRayNormalMap ->VRayMtl (bump front and back) -> VRay2Sided

Thanks!

[Alfred.DeFlaminis · Accepted solution]

Hello @Anonymous,

This may be a better question for the Chaosgroup forums, but my first thought is that they are being gamma corrected.  When you select the map, please try overriding the gamma to 1 for the normals map in the explorer window where you pick your texture toward the bottom.  The VrayHDRI loader is faster than the 3ds Max default bitmap loader for Vray, so in many cases it's nice to use it, but let's start with regular bitmap loader with gamma override before we move on.  In general, normal maps should never be gamma adjusted.  It's difficult to say if a channel needs to be flipped without access to the file to test on, especially since I'm not familiar with Knald.  It may be worthwhile to make sure they are working properly on a regular VrayMtl first and then move those maps to the 2sided mtl.  Please let me know how it goes.  

Best Regards,

[Alfred.DeFlaminis]

Hello @Anonymous,

I just wanted to follow up here, any progress on this issue?

Best Regards,

[kgokhangurbuz]

Hi;

Can you please save your file as Archive and send it to me, i'd like to take a closer look.

Regards;

[Anonymous]

Thank you for the advice! The issue did seem to be arising from the normal map being gamma corrected. I attempted not gamma correcting as well as using VRayHDRI Inverse gamma and the dark areas seemed to disappear.

When increasing the bump value I did get a warning: "Texture "Map ___" in Material "Material ___" returned an invalid bump normal (XYZ 1.#QNAN...)" but clamping the normal map output seemed to eliminate the warning after some trial and error.

Thanks for the quick help :)!

[Alfred.DeFlaminis]

Happy to help @Anonymous!

Thanks for the confirmation and for the extra information about the normal map error.  Kudos for the extra info!  

Best Regards,

[marksman123]

Thanks!!! Importing the gamma at 1.0 worked! I've had this problem for like 2 years and pretty much avoided using normal maps for this reason. Awesome!

[Alfred.DeFlaminis]

Hello @marksman123,

It happens to all of us at one point or another!  Thanks for the confirmation that this helped, I love reading those kinds of updates.  

Ideally, Max should default normal maps at 1.0 gamma.  That would make a good feature request...  

Have a good one @marksman123 and best regards!