I´m looking into uses of high amount of samples in multisampling. If I have an RGBA8 framebuffer and render to it using multisample with many samples, say 32, dithering on per-sample level should yield a reasonably accurate 8-bit color from the 32 samples in 4-bit color when resolved. The spec (4.5) seems a bit scary though (glBlitFrameBuffer):
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. If the source formats are ﬂoating-point or normalized types, the sample values for each pixel are resolved in an implementation-dependent manner. If the source formats are depth values, sample values are resolved in an implementation-dependent manner where the result will be between the minimum and maximum depth values in the pixel.
What does that even mean?
Is there a way to do it in a cross implementation defined manner?