The RenderToolbox is a set of Matlab software tools that aid in the modeling and rendering of images for use in psychophysical experiments. The toolbox, which we are making freely available, has several important features. First, it allows the user to model scenes in the popular Maya software package and export these into the remainder of the rendering pipeline. Second, although the toolbox inherits the scene geometry from the Maya modeler, it allows the user to associate full spectral reflectance functions and parametric BRDFs with each object, and full spectral power distributions with each illuminant. The toolbox then parses the scenes and associated reflectance/illuminant parameters and passes these to either of two renderers. These are Radiance and Physically Based Rendering Tools (PBRT). It invokes the renderers on a wavelength-by-wavelength basis to produce a hyperspectral image of the scene. The fact that the toolbox transparently supports two renderers allows easy comparison of their performance. In addition, the toolbox is configured to make it easy to re-render the same scene geometry with different choices of reflectance/illuminant parameters. Fourth, the package provides support for converting the hyperspectral image to standard color representations. Finally, the package supports parallel rendering of the separate wavelength images if a computer cluster is available. Several example scenes are included with the toolbox to demonstrate its use and to compare the two renderers' performance. The simplest example, a uniformly reflective surface and a single point-light source, yields two nearly identical images. Each of these matches an analytical prediction based on the light's spectral power distribution and surface's reflectance function. A second example scene includes a single sphere with uniform reflectance under a distant point-light source. Again, images rendered by Radiance and PBRT are well-matched to each other and to the directly calculated image based on the Ward model of surface reflectance. The close agreement of the two renderers with each other and with direct calculations for simple scenes provides added confidence that each renderer is doing a good job simulating physical light flow.