This paper examines the feasibility of implementing core algorithms from Radiance using a new type ray tracing engine optimized for highly parallel graphics hardware environments. It presents solutions to a number of implementation challenges. First, the Radiance data format is reinterpreted as a set of buffered data arrays compatible with graphics processing unit (GPU) memory. Second, the ray tracing core of the Radiance RPICT and RTRACE programs for global illumination calculations of scenes and discrete sensors is broken up into a number of small GPU programs that execute in parallel. Third, command-line user settings are declared as variables on the GPU with scopes appropriate to their functions. As a proof of concept, the paper presents a reference implementation using the OptiX™ ray tracing engine that produces images indistinguishable from Radiance up to twenty times faster for scenes with a palette of common materials.