These topics describe what the mental ray renderer can do, and explain how it accomplishes these effects. For more technical
detail about mental ray capabilities, see the mental ray Reference, available from Help menu 
Additional Help, and the books Programming mental ray and Rendering with mental ray, both by Thomas Driemeyer.
The mental ray renderer can generate reflections and refractions by ray tracing. Ray tracing traces the path of rays sampled from the light source. Reflections and refractions generated this way are physically accurate.
The mental ray renderer can generate shadows by ray tracing. Ray tracing traces the path of rays sampled from the light source. Shadows appear where rays have been blocked by objects. Ray-traced shadows have sharp edges.
Motion blur is a way to enhance the realism of a rendered animation by simulating the way a real-world camera works. A camera has a shutter speed, and if significant movement occurs during the time the shutter is open, the image on film is blurred.
Depth of field is a way to enhance the realism of a rendering by simulating the way a real-world camera works. With a broad depth of field, all or nearly all of a scene is in focus. With a narrow depth of field, only objects within a certain distance from the camera are in focus.
Caustics are the effects of light cast onto an object via reflection off or refraction through another object.
Global illumination enhances the realism in rendered images by simulating all light interreflection effects in a scene (except caustics). It generates such effects as "color bleeding," where for example, a white shirt next to a red wall appears to have a slight red tint.
Volume shading shades a three-dimensional volume, rather than a surface. Typically, volume shaders provide atmospheric effects such as mist and fog.
Displacement shading with the mental ray renderer is similar to Displacement mapping of standard materials. One advantage of using mental ray displacement is that the additional polygons of displaced surfaces are stored only in the mental ray scene database, not in your 3ds Max scene, so they do not increase the memory requirements of your scene, except at render time. This can be a big improvement in performance over displacement mapping with standard materials and the scanline renderer.
Contour shading lets you render vector-based contour lines. Contours are similar to the ink component of the Ink 'n Paint material.
