Hi,
I just stumbled across an issue with deferred shading, that I never heard of before.
When I apply the lights to the gbuffer, I draw screen-aligned quads, using an orthographic projection matrix.
Today I realized that this completely breaks mipmap selection for, say projected lights. Since ds/dx and dt/dy are not dependend on the surface I shade (the screen-quad is not the surface!), mipmapping seems to be disabled for the light´s texture (or any other texture I sample in the shading pass)?! The problem becomes especially apparent when sampling an environmap cubemap.
How to circumvent the problem?