fdo-mirrors/mesa
1
0
Fork 0
mirror of https://gitlab.freedesktop.org/mesa/mesa.git synced 2026-01-03 00:40:09 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Minor clean-ups of variable scopes, initializations, etc.

Browse source 
New comments discussing FIXED_FRAC_BITS, SUB_PIXEL_BITS, max viewport size
and rasterization accuracy.
This commit is contained in:
Brian Paul 2004-02-15 16:21:07 +00:00
parent 0200947f5e
commit 7c4a61c57f
1 changed files with 52 additions and 30 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

82
src/mesa/swrast/s_tritemp.h
View file

@ -1,8 +1,8 @@
/*
* Mesa 3-D graphics library
* Version: 5.1
* Version: 6.1
*
* Copyright (C) 1999-2003 Brian Paul All Rights Reserved.
* Copyright (C) 1999-2004 Brian Paul All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
@ -63,6 +63,34 @@
* This code was designed for the origin to be in the lower-left corner.
*
* Inspired by triangle rasterizer code written by Allen Akin. Thanks Allen!
*
*
* Some notes on rasterization accuracy:
*
* This code uses fixed point arithmetic (the GLfixed type) to iterate
* over the triangle edges and interpolate ancillary data (such as Z,
* color, secondary color, etc). The number of fractional bits in
* GLfixed and the value of SUB_PIXEL_BITS has a direct bearing on the
* accuracy of rasterization.
*
* If SUB_PIXEL_BITS=4 then we'll snap the vertices to the nearest
* 1/16 of a pixel. If we're walking up a long, nearly vertical edge
* (dx=1/16, dy=1024) we'll need 4 + 10 = 14 fractional bits in
* GLfixed to walk the edge without error. If the maximum viewport
* height is 4K pixels, then we'll need 4 + 12 = 16 fractional bits.
*
* Historically, Mesa has used 11 fractional bits in GLfixed, snaps
* vertices to 1/16 pixel and allowed a maximum viewport height of 2K
* pixels. 11 fractional bits is actually insufficient for accurately
* rasterizing some triangles. More recently, the maximum viewport
* height was increased to 4K pixels. Thus, Mesa should be using 16
* fractional bits in GLfixed. Unfortunately, there may be some issues
* with setting FIXED_FRAC_BITS=16, such as multiplication overflow.
* This will have to be examined in some detail...
*
* For now, if you find rasterization errors, particularly with tall,
* sliver triangles, try increasing FIXED_FRAC_BITS and/or decreasing
* SUB_PIXEL_BITS.
*/
@ -558,24 +586,18 @@ static void NAME(GLcontext *ctx, const SWvertex *v0,
*/
{
int subTriangle;
GLfixed fx;
GLint subTriangle;
GLfixed fxLeftEdge = 0, fxRightEdge = 0;
GLfixed fdxLeftEdge = 0, fdxRightEdge = 0;
GLfixed fdxOuter;
int idxOuter;
float dxOuter;
GLfixed fError = 0, fdError = 0;
float adjx, adjy;
GLfixed fy;
#ifdef PIXEL_ADDRESS
PIXEL_TYPE *pRow = NULL;
int dPRowOuter = 0, dPRowInner; /* offset in bytes */
GLint dPRowOuter = 0, dPRowInner; /* offset in bytes */
#endif
#ifdef INTERP_Z
# ifdef DEPTH_TYPE
DEPTH_TYPE *zRow = NULL;
int dZRowOuter = 0, dZRowInner; /* offset in bytes */
GLint dZRowOuter = 0, dZRowInner; /* offset in bytes */
# endif
GLfixed zLeft = 0, fdzOuter = 0, fdzInner;
#endif
@ -659,31 +681,31 @@ static void NAME(GLcontext *ctx, const SWvertex *v0,
}
if (setupLeft && eLeft->lines > 0) {
const SWvertex *vLower;
GLfixed fsx = eLeft->fsx;
fx = FixedCeil(fsx);
const SWvertex *vLower = eLeft->v0;
const GLfixed fsx = eLeft->fsx; /* no fractional part */
const GLfixed fsy = eLeft->fsy;
const GLfixed fx = FixedCeil(fsx); /* no fractional part */
const GLfloat adjx = (GLfloat) (fx - eLeft->fx0); /* SCALED! */
const GLfloat adjy = eLeft->adjy; /* SCALED! */
GLfixed fdxOuter;
GLint idxOuter;
GLfloat dxOuter;
fError = fx - fsx - FIXED_ONE;
fxLeftEdge = fsx - FIXED_EPSILON;
fdxLeftEdge = eLeft->fdxdy;
fdxOuter = FixedFloor(fdxLeftEdge - FIXED_EPSILON);
fdError = fdxOuter - fdxLeftEdge + FIXED_ONE;
idxOuter = FixedToInt(fdxOuter);
dxOuter = (float) idxOuter;
dxOuter = (GLfloat) idxOuter;
span.y = FixedToInt(fsy);
/* silence warnings on some compilers */
(void) dxOuter;
fy = eLeft->fsy;
span.y = FixedToInt(fy);
adjx = (float)(fx - eLeft->fx0); /* SCALED! */
adjy = eLeft->adjy; /* SCALED! */
#ifndef __IBMCPP__
(void) adjx; /* silence compiler warnings */
(void) adjy; /* silence compiler warnings */
#endif
vLower = eLeft->v0;
#ifndef __IBMCPP__
(void) vLower; /* silence compiler warnings */
#endif
(void) adjx;
(void) adjy;
(void) vLower;
#ifdef PIXEL_ADDRESS
{
@ -694,7 +716,7 @@ static void NAME(GLcontext *ctx, const SWvertex *v0,
#endif
/*
* Now we need the set of parameter (z, color, etc.) values at
* the point (fx, fy). This gives us properly-sampled parameter
* the point (fx, fsy). This gives us properly-sampled parameter
* values that we can step from pixel to pixel. Furthermore,
* although we might have intermediate results that overflow
* the normal parameter range when we step temporarily outside