Ext3h
Regular
You are right, it's not much different. Except that back then VRWorks only did multi-resolution, means different viewport, but only a single projection matrix. Going by the GL_AMD_vertex_shader_viewport_index extension, AMD features something just as capable as Nvidias fast geometry shader path, so there shouldn't be any actual difference in performance.What you are describing is very similar to NVIDIA multirate shading tech in VRWorks already supported on Maxwell
But you don't need to allow arbitrary quads for viewports in order to do lens matched shading. You can just subdivide into 12 or 16 rectangles right away, and just apply an adjusted projection matrix to the vertex dispatched by the GS to each single viewport. Apart from trading masking for rectangular viewports, that's exactly the same as what Nvidia now showed.
(Well, you can't divide into more than 9 viewports on Maxwell, because that's the limit for the viewport array size on Maxwell. Interesting enough, GCN allowed 16 viewports from the beginning, just as Pascal does now.)