How to guess if a normal map needs gamma or not

[vlado]

Someone asked me if there's a way to guess if a normal map needs to be loaded with gamma 2.2 or 1.0; you can tell that by loading the map with Render > View Image File... then right-click on a region of the map that seems "flat" and look at the RGB values you get. If they are around 128,128,255 - then the map does not need gamma override. If you get values around 50,50,255 then you need load the map with a gamma override of 1.0.

Additionally, you can guess if the map needs to have its red/green channels flipped (at least when mapped on a default plane); if you look just at the red channel of the loaded bitmap, if must look as though the surface is illuminated from the left; if you look at the green channel, it must look as though the surface is illuminated from above. If they look different, then you'll need to flip and/or swap the red and green channels accordingly.

Best regards,
Vlado

[^Lele^]

sticky please!

[AndresAhumada]

Very Nice tip.... thanks Vlado.

[jackieteh]

Hi Vlado, can i check bump map and reflection map with this method?

[francomanko]

ok so just a bit confused, ive only ever had to flip the green channel depending on if its opengl or directx, i dont think anyone flips the red. Also im pretty sure every normal map ive seen, the red is as if illuminated from the right. Do you mean the mapping is left to right, ie X: -1 to +1 : Red: 0 to 255? As opposed to it looking like the lightsource is on the left?

[^Lele^]

ok so just a bit confused, ive only ever had to flip the green channel depending on if its opengl or directx, i dont think anyone flips the red. Also im pretty sure every normal map ive seen, the red is as if illuminated from the right. Do you mean the mapping is left to right, ie X: -1 to +1 : Red: 0 to 255? As opposed to it looking like the lightsource is on the left?

I think he meant swapping of the channels, not flipping as in image coordinates.

[Oleg_Budeanu]

Make this a feature for next Vray Update. Corona has it, I believe?

[Vizioen]

Make this a feature for next Vray Update. Corona has it, I believe?

Corona can detect whether a normal map has incorrect gamma, not if it's wrongfully flipped

[Oleg_Budeanu]

Corona can detect whether a normal map has incorrect gamma, not if it's wrongfully flipped

Yep, I am talking about incorrect gamma.

[francomanko]

im still confused about the "if you look just at the red channel of the loaded bitmap, if must look as though the surface is illuminated from the left" because its the right for me. (eitherway I've ruined the sticky)

[Vizioen]

Someone asked me if there's a way to guess if a normal map needs to be loaded with gamma 2.2 or 1.0; you can tell that by loading the map with Render > View Image File... then right-click on a region of the map that seems "flat" and look at the RGB values you get. If they are around 128,128,255 - then the map does not need gamma override. If you get values around 50,50,255 then you need load the map with a gamma override of 1.0.

Additionally, you can guess if the map needs to have its red/green channels flipped (at least when mapped on a default plane); if you look just at the red channel of the loaded bitmap, if must look as though the surface is illuminated from the left; if you look at the green channel, it must look as though the surface is illuminated from above. If they look different, then you'll need to flip and/or swap the red and green channels accordingly.

Best regards,
Vlado

Vlado, I don't like to question your tips, but I just tested this and are you sure it's not the other way around? As in RED needs to be illuminated from the right and GREEN needs to be illuminated from the bottom? Because I have a map that is illuminated from the right in the Red and illuminated from above in the Green. And the only way it looks correct is if I flip the green channel.

[Vizioen]

Or anybody else?

[rezvan23]

Vlado, I don't like to question your tips, but I just tested this and are you sure it's not the other way around? As in RED needs to be illuminated from the right and GREEN needs to be illuminated from the bottom? Because I have a map that is illuminated from the right in the Red and illuminated from above in the Green. And the only way it looks correct is if I flip the green channel.

Can someone explain this red/green situation? I'm confused right now.

Every Quixel Bridge material I import to max (via MSLiveLink) green is illuminated from the top and red is illuminated from the right.

So... which one is correct at last?

[piotrus3333]

with quixel you need to switch ‘flip green’ on.
I just added this to their exporter script.
just two different ways of interpreting normal maps between engines or DCCs

[rezvan23]

with quixel you need to switch ‘flip green’ on.
I just added this to their exporter script.
just two different ways of interpreting normal maps between engines or DCCs

I see. So as Vizioen said above, RED needs to be illuminated from the right and GREEN needs to be illuminated from the bottom. Am I understand correctly?