Problem with Vertex Colors in Cycles

Hey, everyone!

I’ve got a nasty problem with vertex colors not rendering nicely in Cycles. I have imported geometry from Oculus Quill that contains vertex color data. When plug in the vertex colors into the shader via the Attribute node, everything looks fine in the viewport or when rendered in Eevee. But in Cycles I get ugly color banding. Looks like this:

I’ve already searched a lot around the internet and there are some topics where sRGB versus linear or RAW RGB are discussed. Some people talk about adding a gamma correction to the color value but I wasn’t able to achieve anything that way.

My main confusion remains to be: why can Eevee render the vertex colors correctly but Cycles can’t?

Any advise?

Share some minimal files here or on the bug tracker that reproduce the error (blend file and or quill output file).

Shader network screenshot please

Ok, so I’ve created a more lightweight scene that shows the problem. In Oculus Quill you basically have two formats that you can use to export your scene with vertex colors: FBX and Alembic. Both exports can be performed with a “Linear” or a “Gamma” option for the colors. I’ve exported all 4 variations and imported them into a Blender scene:

In this example, the problem is not as glaring as in the example above but you can still see the color banding in the dark tones in the Cycles render while the Eevee render looks ok.

You can download the Blender (2.8) scene here (~26MB):

You can download the 4 exported Quill files here (~1.7MB):

I’d really appreciate if you’d take the time and try to get me out of my misery!