Decode HDR GrabPass?

When HDR is enabled on camera, GrabPass texture does not have RGB values in it. Rather, it has HDR values.

How you decode these values into what they would have been without HDR enabled for the camera?

I've tried using this:

Code (CSharp):

1. DecodeHDR(tex2D(_GrabTexture, IN.screenPos.xy / IN.screenPos.w), unity_SpecCube0_HDR);

But it does not produce desired result.

 

I believe DecodeHDR is for decoding texture assets saved in RGBM, not decoding the grab texture. You shouldn't need to do anything special with the grab pass HDR or not. I think the default way Unity displays HDR is just clamping the output between 0.0 and 1.0.

 

Well this is awkward. This absolutely didn't work before. Using the HDR GrabTexture right away would cause everything to become white. But now when I try it works just fine. I've seen this before that sometimes all changes to a shader don't seem to apply instantly sometimes, but rather you need to restart the editor or reimport. That's frustrating considering I spent hours trying to solve this.

 

I'm bumping this, because I've just stumbled across this problem myself. Everything is white in my Blur shader on OpenGL, and it works just fine on DirectX.

The weird thing is that I only get it on OpenGLCore and never on DirectX.

Does anyone have any ideas?

 

I have the opposite problem, I am trying to get HDR values from a render texture, but I can only get SRGB values from 0 to 1. How do I extract HDR values from SAMPLE_TEXTURE2D?