Suppose I format a renderbuffer like so:
glRenderbufferStorageMultisample(GL_RENDERBUFFER, sampleCount, GL_R32UI, imageWidth, imageHeight);
where sampleCount >= 2.
And suppose I attach it to an FBO, draw some stuff into it, blit it to a non-multisampled FBO to resolve the multisampling, and finally call glReadPixels to get back some unsigned integers (one per pixel) from the resulting image.
What integers will I get?
Might some of them be a blend of multiple samples, or is only one sample per pixel chosen in this case (presumably because an integer-based format is not considered to be blendable in this context), with the other samples being discarded? Or does something else happen?
On page 511 of the OpenGL 4.5 spec, under section 18.3.1 "Blitting Pixel Rectangles", it says (emphasis added):
If the read framebuffer is multisampled (its effective value of SAMPLE_BUFFERS is one) and the draw framebuffer is not (its value of SAMPLE_BUFFERS is zero), the samples corresponding to each pixel location in the source are converted to a single sample before being written to the destination. filter is ignored. If the source formats are integer types or stencil values, a single sample’s value is selected for each pixel.
So it choses one sample per pixel, without specifying which of the samples.