Sprites

To be able to draw some ripple images on a force field surface, we need to apply image texture on solid, but continue producing secondary rays after primary intersection. With such a trick we can simulate a glass without refraction effect a.k.a. a transparent solid.

Using simple planar mapping from different directions on sphere surface, you can get nice pictures.

To be able to draw these images, you just need to be sleep deprivated for several day in despare to finish a rendering competition...

Using derivatives from image textures in order to perturb secondary ray direction gives you nice ripple effect. The implementation of force field material (forcefield.h) can be found in ../rt/materials folder.