Interactive Shadowed Caustics Using Hierarchical Light Volumes

Abstract

The interplay of refracted light and shadow is an important component of underwater scenes. Full and correct interactive rendering of refracted caustics remains beyond the capabilities of even the most recent graphics hardware. We present an interactive caustic-beam rendering algorithm that improves on prior methods in three important ways: it uses a hierarchical structure over the refracting object to speed culling and clamping of light beams; it correctly handles shadowing by objects above the water surface, and can eliminate computation for shadowed regions; and it efficiently uses GPU vertex programming to reduce the rendering cost for caustic beams. In addition, we present a variation to the algorithm using a floating point texture for scaled vector rather than intensity accumulation for more correct caustic appearance at a cost in performance.