Visualization of Coherent Structures of Light Transport

The radiance structure inside the glass sphere (Figure 1) results from total internal reflection that allows light to reach points that are otherwise in shadow due to refraction perturbing light paths towards the center. The hard boundaries of these structures mark the narrow stripes where light travels around the sphere several times by total internal reflection, after it just managed to enter the sphere at extremely shallow angles. The stripes leading of the sides of the sphere are also caused by light traveling on such multiple total internal reflection paths before barely managing to exit the sphere. The rest of the radiance field conforms with what is intuitively expected of the caustics caused by glass spheres.