The Filtering of 3d textures

Solid textures or textures defined over 3d have provided computer graphics with a new set of tools. Using these tools we can obtain effects which were difficult, if not impossible, to obtain with 2d texture mapping methods. These textures are simple to implement using either scan line renderers or ray-tracers. Research in this area has focused on the generation and rendering of these textures with little consideration of the sampling and filtering problems which arise when these textures are used. The de-facto answer to the filtering problem has been to clamp the signal so that no aliasing frequencies appear in the texture . Clamping a signal can cause variety of problems including energy loss and cross-spectrum energy leaks, we show how these artifacts can arise in fairly simple examples. We propose a filtering method for filtering 3d textures which uses a box shaped kernel. A variety of filters can then be applied over this box. This method is illustrated by using two kernels: the first aligned with the tangent plane of the surface; the second aligned along the ray from the intersection point to the eye.