Penn Arts & Sciences Logo

What Are Those Images?

This is a variant of Adelson's checker-shadow illusion.  Rather than being drawn manually, this version was modeled using python-driven Blender and rendered from a scene description using the Mitsuba Renderer and our Matlab RenderToolbox3.  The materials required to produce this scene are provided as part of the open-source Rendertoolbox3 distribution.  A fuller description of the scene, as well as of RenderToolbox3, may be found at the gitHub Rendertoolbox3 repository (this image is produced as part of the BlenderPython Example Scene).  Although we have not (yet) used this image in psychophysical experiments, we have studied other variants of the checker-shadow illusion (e.g., Hillis and Brainard, 2007 as well as in ongoing research).
This is one image of a stereo pair that we are using in studies of how well humans can discriminate changes of scene illumination and changes in object surface reflectance.  The images are generated using our RenderToolbox3 software (see above) and displayed on a computer-controlled stereo haploscope.  This work is in collaboration with the Hurlbert Lab at the Univerity of Newcastle.
This image shows the 'source blocks' for our studies of color constancy using a natural task.  Subjects use a mouse to select source blocks and construct a model that matches a test configuration of blocks.  The test configuration and constructed model are not shown here.  This is work being done primarily by Ana Radonjic, a post-doc in the Brainard Lab.
This image is a graphics rendering based on a illusion developed by Lotto and Purves.    The pip on the top side of the cube has (essentially) the same RGB values as the pip on the lower right side of the front fase of the cube, but looks quite different.  The pip on the upper left side of the cube was rendered with the same reflectance as the pip on the top.  The fact that this latter reflectance match looks more similar to the pip on the top than the RGB-matched pip illustrates the human visual system's color constancy.  We have employed stimuli such as this one in psychophysical experiments.  As with the other images on this page, this image was produced using RenderToolbox3.  The files needed to produce it are provided as part of the RenderToolbox3 distribution.  See here for full description.