RealityKit texture sampling behaviour

Hi @imak604

When you say "for example an RGB value of 0x7f0000 (R = 0.5, G = 0, B = 0) would be seen as 0.21, 0, 0 in the shader", do you mean the shader renders the red channel (in the RealityKit scene) as 0.21 instead of 0.5? If so, light is to blame. If you want the surface to be unaffected by light, replace PreviewSurface with UnlitSurface.

If I misunderstood your question, please point me in the right direction so I can help.

Hey there, thanks for chiming in. The issue is that the texture sampler in the shader graph seems to see a (0.5,0,0) pixel in the texture image as something like (0.21,0,0) for example. The equivalent metal operation would be something like:

constexpr sampler s(address::clamp_to_edge, filter::linear); float4 s = tex.sample(s, float2(0.4,0.2)); // expected float4(0.5, 0, 0), got float4(0.21, 0, 0);

Does lighting affect the value of the texture sampler?

Here's a more direct example of the issue... in the image below, the upper gradient is a material that uses a textured image, the bottom gradient is generated from within the shader. The two gradients should be identical but the image textured material is noticably darker in the middle ranges. I imagine there's a reason for this, anybody know why the texture sampler behaves like this?

gradient image texture:

gradient shader graph: