OpenGL.GL.EXT.framebuffer_multisample_blit_scaled

OpenGL extension EXT.framebuffer_multisample_blit_scaled

This module customises the behaviour of the OpenGL.raw.GL.EXT.framebuffer_multisample_blit_scaled to provide a more Python-friendly API

Overview (from the spec)

This extension relaxes some of the restrictions associated with multisample resolve operations, specifically to allow a combined resolve and scale operation through a single call to BlitFramebuffer. It also adds two new filter types to control the quality of the combined scaled resolve operation.

In traditional multisampled framebuffer rendering, color samples must be explicitly resolved via BlitFramebuffer before any other operation on the resulting pixel values can be performed. This multisample resolve operation must be done using a BlitFramebuffer call where the dimensions of the source and destination rectangles are identical. If the resulting pixel values need to be copied to a texture with different dimensions, these resolved values can then be scaled with a second call to BlitFramebuffer.

By requiring two separate calls to BlitFramebuffer, the quality of final image can be maintained to a certain degree. The samples are first resolved, and then these resolved values can be filtered to produce the final image. This image quality comes at the price of increased memory usage and lower performance. However, the scaling blit can still introduce artifacts, particularly if it is done with a simple bilinear filter.

The new filter types introduced by this extension allow the scaled resolve to be done with a single call to BlitFramebuffer. Not all samples from the read framebuffer are required to be be used when producing the final pixel values, and there may be a loss in quality when compared to an image produced by a separate resolve and scale. However, the single-pass scaled resolve blit should be faster than the traditional two-pass resolve then scale blits.

The official definition of this extension is available here: http://www.opengl.org/registry/specs/EXT/framebuffer_multisample_blit_scaled.txt