Please, Does anyone know why this is happening ?

OliverJSR

The diffuse textures seem fine in the substance viewer but when I try to export them they come out too bright and its ruining all my work. been trying ages to find out whats doing it.

poopipe

If you're exporting 16 bit maps to ue4 this will happen. Ue4 assumes the maps are using linear color space and applies a gamma curve to them. 

Add  pow(1/2.2) after the colour maps  (basecolor and emissive) to bring them back into the right range.

OliverJSR

its not a ue4 thing. because the actual texture is exporting too brightly from substance 

Octo

Is it an sRGB thing then?
https://forum.allegorithmic.com/index.php?topic=8178.0

OliverJSR

thanks octo, that seems to work. this setting was still ticked the wrong way
(for anyone else who experiences this problem)
 

poopipe

This is definitely a colour space issue. the viewer needs to interpret the data correctly - many (ue4 included) will assume that a 16bit per pixel file should be read as if the data is in linear space and thus will apply a gamma curve to it for viewing. 

We use painter to output 16bit sRGB diffuse maps at work and haven't had any issues so it does work.

I don't use marmoset but I expect you just need to tell it to treat the texture as sRGB - which is what painter outputs by default