gluPartialDisk renders a partial disk on the $ z ~=~ 0 $ plane. A partial disk is similar to a full disk, except that only the subset of the disk from start through start + sweep is included (where 0 degrees is along the + yaxis, 90 degrees along the + x axis, 180 degrees along the -y axis, and 270 degrees along the - x axis).The partial disk has a radius of outer, and contains a concentric circular hole with a radius of inner. If inner is 0, then no hole is generated. The partial disk is subdivided around the z axis into slices (like pizza slices), and also about the z axis into rings (as specified by slices and loops, respectively).
With respect to orientation, the +z side of the partial disk is considered to be outside (see gluQuadricOrientation). This means that if the orientation is set to GLU_OUTSIDE, then any normals generated point along the + z axis. Otherwise, they point along the -z axis.
If texturing is turned on (with gluQuadricTexture), texture coordinates are generated linearly such that where $ r ~=~ "outer" $, the value at ( r, 0, 0) is (1.0, 0.5), at (0, r, 0) it is (0.5, 1.0), at (-r, 0, 0) it is (0.0, 0.5), and at (0, - r, 0) it is (0.5, 0.0).