Abstract: In this paper we present an improved technique for interactive rendering of caustics using programmable graphics hardware. Previous real-time methods have used simple prisms for the caustic volumes and a constant intensity approximation at the receiver. Our approach uses interpolated caustic volumes to render smooth high-quality caustics. We have derived a simple formula for evaluating the density of wave-fronts along a caustic ray, and we have developed a precise method for rendering caustic volumes bounded by bilinear patches. The new optimizations are well suited for programmable graphics hardware and our results demonstrate interactive rendering of caustics from refracting and reflecting surfaces as well as volume caustics. In contrast to previous work, our method renders high quality caustics generated by specular surfaces with much fewer polygons.