For this recipe, we extend the geometry shader's instancing approach to create environment maps that were introduced in the previous recipe, Implementing multithreaded cubic environment mapping, and generate a dual paraboloid environment map. A dual paraboloid map (DPM) requires only two render targets instead of the six used in the cube maps, therefore requiring less texture memory. However, there is also no built-in hardware support for sampling a DPM that instead requires a manual implementation of the sampling based on the reflection vector.