The derived point size is defined to be the provided with glPointSize modulated with a distance attenuation factor. Otherwise, the threshold size is set to be the diameter of the rasterized point, while the alpha component is modulated accordingly, to compensate for the larger area. The alpha of a point is calculated to allow the fading of points instead of shrinking them past a defined threshold size. Points do not affect the current color. This extension doesn't change the feedback or selection behavior of points.
Enumerant values are unchanged.
SGI implementations which previously provided this functionality should support both forms of the extension.