What is texture mapping and how is it different from what VolumePro renders?
An alternative way of rendering a volume data set is to use the 3D texture mapping capability of a conventional 3D polygon graphics system. In this method, a volume data set is classified or converted to RGBA and loaded into the texture memory. Rendering proceeds by texturing mapping a series of planes perpendicular to the view direction, then compositing them into the frame buffer. There are several shortcomings to this approach. First, there are no practical ways to calculate and use gradients or surface normals to implement realistic shading and illumination, a very important requirement of usable 3D visualization. VolumePro® provides a Phong lighting calculation at every sample point to highlight surfaces, no matter what classification function is applied. Second, only some of the 3D graphics systems at PC price points support 3D texture mapping, and of those that do, very few can approach the 128- or 256-Mbyte volume capacity of the VolumePro® 500. Systems without adequate texture
