normal maps with vray - what is the correct workflow

[Rufos]

hey to all

a little question - i unwraped my model in max - exported to obj and imported in mudbox.

after editing my mesh and textures i exported normal maps from mudbox - now is the issue, i tried to load the normal map to vraynormal bump map and nothing happened the mesh stays clean with out any deformation

can some one put some light on this topic - what is the correct workflow with normal maps using vray .

thanks

Dan

[vlado]

Does it work with the regular Normal map?

Best regrds,
Vlado

[Rufos]

i tried the standard normal map and it seems to work but not correct - and the effect is very small

maybe im doing some thing wrong

thanks
Dan

[vlado]

You need to set the bump strength to 100 in the actual material - did you do that?

Best regards,
Vlado

[trixian]

also, gamma?
Make sure its loaded with gamma 2.2 if needed.
Not using mudbox, I'm not sure if it actually writes a linear normal map.

[yyk]

also, gamma?
Make sure its loaded with gamma 2.2 if needed.
Not using mudbox, I'm not sure if it actually writes a linear normal map.

I may have something confused here but I thought Vray normal map only works when you override gamma to 1,0 when loading the bitmap.

[trixian]

News to me. You can input any map into its input slot, so I think you could easily use any image with gamma x.
Can any Chaotic-Neutral person confirm or deny?

[Rens]

Loading in a normal map with any gamma other than 1.0 will not work correctly. It will still have an effect of course but it won't work as intended.
This is because normal maps rotate around the face normal, the base or zero-rotation point is set at RGB .5 .5 1.0. So a map with that colour as a normal map will render the same as a map without a normal map.

As a gamma operation shifts the midpoint it will shift the base rotation as well. If you put a gamma curve on the RGB .5 .5 1.0 map and then render you have basically rotated all normals in a certain direction.

BTW a map with that colour is useful for blending with a normal map image to blend in areas where the effect isn't as strong.

Also, if you want to do operations on a normal map image like gamma or multiply, you can subtract with .5 .5 1.0 to bring the base down to zero. Then do the operations and add .5 .5 1.0 again. Good for adding contrast e.g. making steeper slopes.

[trixian]

Even if the normal map is sRGB?
A lot of the normal maps I find are allready sRGB and load as incredibly bright (aka wrong gamma) if gamma is set to 1 on load. I then load them with gamma 2.2 (aka inverse gamma) to get the image to output the proper values.
Your 0.5,0.5,1.0 should then read as 128,128,255 with your colour picker.
Top image is loaded with gamma 2,2 (or "automatic" in 2014 with proper LWF)
Bottom loaded with gamma 1.0

[vlado]

Well obviously in that case you'll have to load it with gamma

That's what I'm talking about when I'm trying to explain that the software can't think for you [And it's also what irks me when people say that 'software X' does it automagically - which is another way of saying that nobody knows what it does...]

Best regards,
Vlado

[trixian]

Well during the last few years after getting all the LFW jigsaw pieces together, it still seems topics like gamma and linear image-data gets people really confused.
Back in the days we (many many years ago) we had no proper documentation, and different apps handled this in different ways. Even the max (and combustion) devs refrained from bringing up the topic of gamma in threads where this was clearly an issue. The only people I knew that had any sort of understanding on this issue were people who were unrelated to my field, but had learned about gamma correction and colour profiles in regards to print. Obviously they didn't bother to correct the erroneous ways of me and my colleagues .

Anyone who uses the word "AutomaGically" in a sentence should be slapped with a trout.

[Rens]

Top image is loaded with gamma 2,2 (or "automatic" in 2014 with proper LWF)
Bottom loaded with gamma 1.0

The bottom one looks correct, I'll try to upload some pictures to clarify a bit.

[trixian]

The bottom one is definitely not correct.

The examples I posted are not really the best, as there are no completely flat areas to read pixel values from, but when baking my own maps from Zbrush or directly in max, the flat colour (128,128,255) looks like the top one.

My own bakes are of course already linear, so I load them with the corresponding gamma, but many normal maps found online, (and generated from photos by certain programs) are sRGB, and must be loaded as 2.2 gamma as my example above shows.

[Rens]

After some testing I have to admit that the issue is a lot more complicated than I thought. I saved an EXR and a JPEG from both Photoshop and Nuke with 0.5 0.5 1.0 value, making four images. Then loading in each with both 2.2 and 1.0 gamma.
The only one that is 100% correct so far is the EXR from Nuke, with both gamma settings. Also, there's a difference in the JPEGs only when you enable or disable global max gamma correction. Max 2012 here.

I'll post the pictures tomorrow!

[trixian]

Guessing your exr has the gamma defined in the file header? Does it ignore your manual gamma settings on load?
Or are Exr's always assumed linear regardless?