Gamma Correction unavoidable

Support
1

https://gitlab.kitware.com/vtk/vtk/-/issues/19849

In https://github.com/Kitware/VTK/blob/master/Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx,

void main() { float gamma = 2.2;

// for each sample in the multi sample buffer...
ivec2 itexcoords = ivec2(floor(textureSize(tex) * texCoord));
vec3 accumulate = vec3(0.0,0.0,0.0);
float alpha = 0.0;

for (int i = 0; i < samplecount; i++)
{
  vec4 sampleValue = texelFetch(tex, itexcoords, i);
  // apply gamma correction and sum
  accumulate += pow(sampleValue.rgb, vec3(gamma));
  alpha += sampleValue.a;
}

// divide and reverse gamma correction
accumulate /= float(samplecount);
gl_FragData[0] = vec4(pow(accumulate, vec3(1.0/gamma)), alpha/float(samplecount));

}

is done if MSAA ON and regardless of SRGB How do I turn it off? I guess there is no way,

Can anyone fix it to do gamma correction only for SRGB?

2

It appears that this may be a bug. It seems that when MultiSamples is enabled, the framebuffer color attachment is assumed to be in sRGB format. @killer3d, do you have a test case that confirms this? That would be helpful in validating this assumption and addressing the issue.

3

The test is very simple, By default SRGB is false on window, so even with the default settings of VTK, it always does Gamma correction in resolve shader.