overlay blending - Painter - Photoshop - Unreal

[ccimbaro]

Hi Substance team,

I hope you're well, I have an issue currently in our pipeline and maybe you can answer us.
Currently our pipeline is quite simple:

- we create a set of unique maps per object

This is the painter one


This is the unreal one


As you can see the result is quite similar, so all good.

- After that, we apply 3 tiling detail sets of normal, albedo gray scale and roughness, those sets are controled by mask and apply in overlay blendmode except the normal which is blend in detail normal:

here's the painter render



The UV:


Here's the Unreal render:


The UV:


And here's the photoshop render on albedo:


The tiling is not set for the photoshop version because it was to long for the test but you can see color value are good and mask are apply well.

As you can see, photoshop and unreal are quite the same result (a bit to bright in UE4 due to unlit mode to isolate albedo), but painter not. I know that you have the same overlay blending method, so I search the reason why the render is so different in Painter.
I allready check for post processing, gamma/tone mapping, in fact the result will never be 1 for 1 but here the result is completly different. Panorama is the same too.
Overlay is apply at 100% in painter, photoshop and unreal, maps apply are verify and identical.
It's seems it's an sRGB issue; because painter convert albedo in sRGB right? And photoshop and Unreal (in our case because normal albedo roughness detail are blend in one map ) are in linear. I remember an option to trigger linear or sRGB for maps in Painter but I don't find it again.

Painter is part of our pipeline and it's a real issue to not get the same result between Painter and Unreal, but currently my master material seems get the good result when I do the blending in photoshop to verify.

If you can explain me where I miss, it should be great,

Have a nice day and see you soon,

[Jeremie Noguer]

Blending in Photoshop is performed in sRGB and blending in Painter is performed in Linear, that's likely where the difference comes from. Overlay is one of the blending modes that has the most disparity between the 2 tools.
Not sure how you do the Overlay blending in Unreal but it's possible that it was built to match Photoshop's result in the first place. You would need to alter the math behind the blend in the Unreal material editor to match Painter's result.

[ccimbaro]

Ho allright thanks jeremie,

But (just to be sure I understand) currently albedo color are convert in sRGB in Painter? So when the blend is opareted if the both albedo are sRGB?
Do you know if their is any way to set a power 2.2 on overlay blend in Painter with our programmer?

At the end in UE4 I import my NNAR (normal red and green channel, albedo, roughness) in mask linear no sRGB, but I power 2.2 my blue channel to get an albedo in sRGB in overlay on my unique alebdo sRGB, so yes all the blending is done in sRGB.

I know linear and non linear are always a big topic, but I was sure for albedo, it was always sRGB, am I wrong?

[ccimbaro]

I think about something,

Is Designer calculate the overlay in sRGB?
Because if yes, we can create a susbtance with input to simulate the blending well and drag this substance in painter, right?

[Jeremie Noguer]

The BaseColor channel outputs sRGB, like any other color channel, but the calculations when blending 2 layers together are done in Linear space, no matter the space in which the channel is.