Abstract: Interactive applications require simplifications to lighting, geometry, and material properties that preclude many effects encountered in the physical world. Until recently only the most simplistic reflections and refractions could be performed interactively, but state-of-the-art research has lifted some restrictions on such materials. This paper builds upon this work, but examines reflection and refraction from the light's viewpoint to achieve interactive caustics from point sources. Our technique emits photons from the light and stores the results in image-space, similar to a shadow map. We then examine various techniques for gathering these photons, comparing their advantages and disadvantages for rendering caustics. These approaches run interactively on modern GPUs, work in conjunction with existing techniques for rendering specular materials, and produce images competitive with offline renderings using comparable numbers of photons.