Blender Git Loki

BGE: RASOffScreen object reimplemented with Renderbuffers.

RASOffScreen was previously using GPUOffScreen object from the gpu library,
which in turn uses textures as render destinations, also when multisample is
requested. This is a problem for Intel integrated as they generally don't
support multisample textures.

ImageRender doesn't need textures as render destination: Renderbuffers are
sufficient because it only read pixels from the render with glReadPixels and
glCopyTexSubImage, both of which work with Renderbuffers.

Therefore, RASOffScreen is reimplemented with Renderbuffers and multisample
offscreen renders are now supported on Intel GMA. The gpu library is no
longer used. There is no API change.