1.1 --- a/src/pvr2/rendbkg.c	Tue Sep 12 12:16:36 2006 +0000
     1.2 +++ b/src/pvr2/rendbkg.c	Wed Jan 03 09:00:17 2007 +0000
     1.3 @@ -1,11 +1,22 @@
     1.4  /**
     1.5 - * $Id: rendbkg.c,v 1.3 2006-09-12 12:16:36 nkeynes Exp $
     1.6 + * $Id: rendbkg.c,v 1.4 2006-12-15 10:17:30 nkeynes Exp $
     1.7   *
     1.8   * PVR2 background renderer. 
     1.9   *
    1.10   * Yes, it uses the same basic data structure. Yes, it needs to be handled
    1.11   * completely differently.
    1.12   *
    1.13 + * PVR2 backgrounds are defined as a set of three fully specified vertexes,
    1.14 + * stored in compiled-vertex format. The vertexes form a triangle which is
    1.15 + * rendered in the normal fashion. Points outside the triangle are rendered
    1.16 + * by extrapolating from the gradients established by the triangle, giving
    1.17 + * an overall smooth gradient across the background. Points are colour-clamped
    1.18 + * prior to output to the buffer.
    1.19 + *
    1.20 + * As a special case, if all three points lie on the same line (or are the same
    1.21 + * point, the third point is used by itself to define the entire buffer (ie
    1.22 + * effectively a solid colour).
    1.23 + *
    1.24   * Note: this would be really simple if GL did unclamped colour interpolation
    1.25   * but it doesn't (portably), which makes this roughly 2 orders of magnitude
    1.26   * more complicated than it otherwise would be.