Method and an apparatus for generating reflection vectors which can be unnormalized and for using these reflection vectors to index locations on an environment map

A method for generating a reflection vector that indexes one of a plurality of faces of a cubic environment map stored in a memory, said method comprising the steps of:

• receiving an eye vector (E) and a normal vector (N);
• producing a reflection vector (R) represented by a first coordinate, a second coordinate, and a third coordinate, wherein the reflection vector is unnormalized when one of the normal vector and the eye vector is unnormalized;
• determining a largest coordinate having the largest magnitude of said first, second, and third coordinates;
• and
• generating a fourth coordinate, and a fifth coordinate, by dividing two of said first, second, and third coordinates by said largest coordinate, wherein said fourth, and fifth coordinates define the location on the cubic environment map where said reflection vector indexes said cubic environment map in said memory.

In a data processing system which renders images, a method of generating reflections off a rendered object by using an environment representation comprising a set of 2-dimensional maps which are independent of a viewer's position, said method comprising:

• receiving an eye vector (E) and a normal vector (N), at least one of which is not normalized;
• producing a reflection vector (R) without vector normalization;
• selecting a selected 2-dimensional map which contains a location indexed by said reflection vector;
• determining said location on said selected 2-dimensional map;
• and
• sampling a reflection shading value at said location in said selected 2-dimensional map.