Real-time multiply recursive reflections and refractions using hybrid rendering

We present a new method for real-time rendering of multiple recursions of reflections and refractions. The method uses the strengths of real-time ray tracing for objects close to the camera, by storing them in a per-frame constructed bounding volume hierarchy (BVH). For objects further from the camera, rasterization is used to create G-buffers which store an image-based representation of the scene outside the near objects. Rays that exit the BVH continue tracing in the G-buffers' perspective space using ray marching, and can even be reflected back into the BVH. Our hybrid renderer is to our knowledge the first method to merge real-time ray tracing techniques with image-based rendering to achieve smooth transitions from accurately ray-traced foreground objects to image-based representations in the background. We are able to achieve more complex reflections and refractions than existing screen space techniques, and offer reflections by off-screen objects. Our results demonstrate that our algorithm is capable of rendering multiple bounce reflections and refractions, for scenes with millions of triangles, at 720p resolution and above 30 FPS.