Autodesk 12812-051462-9011 User Guide 3 - Page 320

Reflective interpolation group Neighboring points to look up Defines how many stored grid points (in an N by N group around the currently rendered point) is looked up to smooth out reflective glossiness. The default is 2, and higher values will "smear" the glossiness more, but are hence prone to more oversmoothing artifacts. In the following illustration, the reflection of the left cup in the floor does not use interpolation, and some grain is evident (here intentionally exaggerated). The floor tiles under the other two cups use a half-resolution interpolation with point lookup set to 2 (center) and 4 (right), respectively. Left: No interpolation; Center: Looking up two points; Right: Looking up four points. The preceding image also illustrates one of the consequences of using interpolation: The foot of the left cup, which is near the floor, is reflected quite sharply, and only the parts of the cup far from the floor are blurry. However, the interpolated reflections of the right cups have a base level of blurriness, due to the smoothing of interpolation, which makes even the closest parts somewhat blurry. In most scenes with weak glossy reflections this discrepancy will never be noticed, but in other cases this can make things like legs of tables and chairs feel "unconnected" with a glossy floor, if the reflectivity is high. To resolve this, you can use the High Detail Distance setting (see following). High detail distance Allows tracing of a second set of detail rays to create a "clearer" version of objects within the specified radius. In the following illustration, all three floor tiles use interpolation but the two on the right use different distances for the detail distance. mental ray Materials | 5575