Underwater Caustics

Caustics are defined as "The light patterns generated on a surface by reflected or refracted light rays." Imaging that you are in a swimming pool and swimming beneath the water. The sides of the pool are not evenly lit. As the light enters through the surface of the water it is refracted and causes areas of shadow to appear on any surface beneath the water line.


This implementation of caustics is physically fake. I do not represent light beams entering and refracting on the water surface. This effect is achieved by tiling a sequence of textures on the terrain for the area under the surface of the water.

Sequence of textures which are tiled over the terrain

This does require the graphics card to support a 3rd texture unit. If you remember from previous blog entries, the terrain already requires 2 texture units, 1 for the terrain texture and 1 for the detail map to add more realism to the scene. From some quick research it looks as though most modern graphics cards support at least 4 texture units so this should not be a problem.