s_tritemp.h

mesa-6.5-minigui源码

/*
 * Mesa 3-D graphics library
 * Version:  6.5
 *
 * Copyright (C) 1999-2006  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"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * Triangle Rasterizer Template
 *
 * This file is #include'd to generate custom triangle rasterizers.
 *
 * The following macros may be defined to indicate what auxillary information
 * must be interplated across the triangle:
 *    INTERP_Z        - if defined, interpolate vertex Z values
 *    INTERP_W        - if defined, interpolate vertex W values
 *    INTERP_FOG      - if defined, interpolate fog values
 *    INTERP_RGB      - if defined, interpolate RGB values
 *    INTERP_ALPHA    - if defined, interpolate Alpha values (req's INTERP_RGB)
 *    INTERP_SPEC     - if defined, interpolate specular RGB values
 *    INTERP_INDEX    - if defined, interpolate color index values
 *    INTERP_INT_TEX  - if defined, interpolate integer ST texcoords
 *                         (fast, simple 2-D texture mapping)
 *    INTERP_TEX      - if defined, interpolate set 0 float STRQ texcoords
 *                         NOTE:  OpenGL STRQ = Mesa STUV (R was taken for red)
 *    INTERP_MULTITEX - if defined, interpolate N units of STRQ texcoords
 *
 * When one can directly address pixels in the color buffer the following
 * macros can be defined and used to compute pixel addresses during
 * rasterization (see pRow):
 *    PIXEL_TYPE          - the datatype of a pixel (GLubyte, GLushort, GLuint)
 *    BYTES_PER_ROW       - number of bytes per row in the color buffer
 *    PIXEL_ADDRESS(X,Y)  - returns the address of pixel at (X,Y) where
 *                          Y==0 at bottom of screen and increases upward.
 *
 * Similarly, for direct depth buffer access, this type is used for depth
 * buffer addressing:
 *    DEPTH_TYPE          - either GLushort or GLuint
 *
 * Optionally, one may provide one-time setup code per triangle:
 *    SETUP_CODE    - code which is to be executed once per triangle
 *    CLEANUP_CODE    - code to execute at end of triangle
 *
 * The following macro MUST be defined:
 *    RENDER_SPAN(span) - code to write a span of pixels.
 *
 * 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.
 */

/*
 * ColorTemp is used for intermediate color values.
 */
#if CHAN_TYPE == GL_FLOAT
#define ColorTemp GLfloat
#else
#define ColorTemp GLint  /* same as GLfixed */
#endif


/*
 * Walk triangle edges with GLfixed or GLdouble
 */
#if TRIANGLE_WALK_DOUBLE
#define GLinterp        GLdouble
#define InterpToInt(X)  ((GLint) (X))
#define INTERP_ONE      1.0
#else
#define GLinterp        GLfixed
#define InterpToInt(X)  FixedToInt(X)
#define INTERP_ONE      FIXED_ONE
#endif


/*
 * Either loop over all texture units, or just use unit zero.
 */
#ifdef INTERP_MULTITEX
#define TEX_UNIT_LOOP(CODE)					\
   {								\
      GLuint u;							\
      for (u = 0; u < ctx->Const.MaxTextureUnits; u++) {	\
         if (ctx->Texture._EnabledCoordUnits & (1 << u)) {	\
            CODE						\
         }							\
      }								\
   }
#define INTERP_TEX
#elif defined(INTERP_TEX)
#define TEX_UNIT_LOOP(CODE)					\
   {								\
      const GLuint u = 0;					\
      CODE							\
   }
#endif



/*
 * Some code we unfortunately need to prevent negative interpolated colors.
 */
#ifndef CLAMP_INTERPOLANT
#define CLAMP_INTERPOLANT(CHANNEL, CHANNELSTEP, LEN)		\
do {								\
   GLfixed endVal = span.CHANNEL + (LEN) * span.CHANNELSTEP;	\
   if (endVal < 0) {						\
      span.CHANNEL -= endVal;					\
   }								\
   if (span.CHANNEL < 0) {					\
      span.CHANNEL = 0;						\
   }								\
} while (0)
#endif


static void NAME(GLcontext *ctx, const SWvertex *v0,
                                 const SWvertex *v1,
                                 const SWvertex *v2 )
{
   typedef struct {
      const SWvertex *v0, *v1;   /* Y(v0) < Y(v1) */
#if TRIANGLE_WALK_DOUBLE
      GLdouble dx;	/* X(v1) - X(v0) */
      GLdouble dy;	/* Y(v1) - Y(v0) */
      GLdouble dxdy;	/* dx/dy */
      GLdouble adjy;	/* adjust from v[0]->fy to fsy, scaled */
      GLdouble fsx;	/* first sample point x coord */
      GLdouble fsy;
      GLdouble fx0;	/*X of lower endpoint */
#else
      GLfloat dx;	/* X(v1) - X(v0) */
      GLfloat dy;	/* Y(v1) - Y(v0) */
      GLfloat dxdy;	/* dx/dy */
      GLfixed fdxdy;	/* dx/dy in fixed-point */
      GLfloat adjy;	/* adjust from v[0]->fy to fsy, scaled */
      GLfixed fsx;	/* first sample point x coord */
      GLfixed fsy;
      GLfixed fx0;	/* fixed pt X of lower endpoint */
#endif
      GLint lines;	/* number of lines to be sampled on this edge */
   } EdgeT;

#ifdef INTERP_Z
   const GLint depthBits = ctx->DrawBuffer->Visual.depthBits;
   const GLint fixedToDepthShift = depthBits <= 16 ? FIXED_SHIFT : 0;
   const GLfloat maxDepth = ctx->DrawBuffer->_DepthMaxF;
#define FixedToDepth(F)  ((F) >> fixedToDepthShift)
#endif
   EdgeT eMaj, eTop, eBot;
   GLfloat oneOverArea;
   const SWvertex *vMin, *vMid, *vMax;  /* Y(vMin)<=Y(vMid)<=Y(vMax) */
   GLfloat bf = SWRAST_CONTEXT(ctx)->_BackfaceSign;
#if !TRIANGLE_WALK_DOUBLE
   const GLint snapMask = ~((FIXED_ONE / (1 << SUB_PIXEL_BITS)) - 1); /* for x/y coord snapping */
#endif
   GLinterp vMin_fx, vMin_fy, vMid_fx, vMid_fy, vMax_fx, vMax_fy;

   struct sw_span span;

   INIT_SPAN(span, GL_POLYGON, 0, 0, 0);

#ifdef INTERP_Z
   (void) fixedToDepthShift;
#endif

   /*
   printf("%s()\n", __FUNCTION__);
   printf("  %g, %g, %g\n", v0->win[0], v0->win[1], v0->win[2]);
   printf("  %g, %g, %g\n", v1->win[0], v1->win[1], v1->win[2]);
   printf("  %g, %g, %g\n", v2->win[0], v2->win[1], v2->win[2]);
   */
   /*
   ASSERT(v0->win[2] >= 0.0);
   ASSERT(v1->win[2] >= 0.0);
   ASSERT(v2->win[2] >= 0.0);
   */
   /* Compute fixed point x,y coords w/ half-pixel offsets and snapping.
    * And find the order of the 3 vertices along the Y axis.
    */
   {
#if TRIANGLE_WALK_DOUBLE
      const GLdouble fy0 = v0->win[1] - 0.5;
      const GLdouble fy1 = v1->win[1] - 0.5;
      const GLdouble fy2 = v2->win[1] - 0.5;
#else
      const GLfixed fy0 = FloatToFixed(v0->win[1] - 0.5F) & snapMask;
      const GLfixed fy1 = FloatToFixed(v1->win[1] - 0.5F) & snapMask;
      const GLfixed fy2 = FloatToFixed(v2->win[1] - 0.5F) & snapMask;
#endif
      if (fy0 <= fy1) {
         if (fy1 <= fy2) {
            /* y0 <= y1 <= y2 */
            vMin = v0;   vMid = v1;   vMax = v2;
            vMin_fy = fy0;  vMid_fy = fy1;  vMax_fy = fy2;
         }
         else if (fy2 <= fy0) {
            /* y2 <= y0 <= y1 */
            vMin = v2;   vMid = v0;   vMax = v1;
            vMin_fy = fy2;  vMid_fy = fy0;  vMax_fy = fy1;
         }
         else {
            /* y0 <= y2 <= y1 */
            vMin = v0;   vMid = v2;   vMax = v1;
            vMin_fy = fy0;  vMid_fy = fy2;  vMax_fy = fy1;
            bf = -bf;
         }
      }
      else {
         if (fy0 <= fy2) {
            /* y1 <= y0 <= y2 */
            vMin = v1;   vMid = v0;   vMax = v2;
            vMin_fy = fy1;  vMid_fy = fy0;  vMax_fy = fy2;
            bf = -bf;
         }
         else if (fy2 <= fy1) {
            /* y2 <= y1 <= y0 */
            vMin = v2;   vMid = v1;   vMax = v0;
            vMin_fy = fy2;  vMid_fy = fy1;  vMax_fy = fy0;
            bf = -bf;
         }
         else {
            /* y1 <= y2 <= y0 */
            vMin = v1;   vMid = v2;   vMax = v0;
            vMin_fy = fy1;  vMid_fy = fy2;  vMax_fy = fy0;
         }
      }

      /* fixed point X coords */
#if TRIANGLE_WALK_DOUBLE
      vMin_fx = vMin->win[0] + 0.5;
      vMid_fx = vMid->win[0] + 0.5;
      vMax_fx = vMax->win[0] + 0.5;
#else
      vMin_fx = FloatToFixed(vMin->win[0] + 0.5F) & snapMask;
      vMid_fx = FloatToFixed(vMid->win[0] + 0.5F) & snapMask;
      vMax_fx = FloatToFixed(vMax->win[0] + 0.5F) & snapMask;
#endif
   }

   /* vertex/edge relationship */
   eMaj.v0 = vMin;   eMaj.v1 = vMax;   /*TODO: .v1's not needed */
   eTop.v0 = vMid;   eTop.v1 = vMax;
   eBot.v0 = vMin;   eBot.v1 = vMid;

   /* compute deltas for each edge:  vertex[upper] - vertex[lower] */
#if TRIANGLE_WALK_DOUBLE
   eMaj.dx = vMax_fx - vMin_fx;
   eMaj.dy = vMax_fy - vMin_fy;
   eTop.dx = vMax_fx - vMid_fx;
   eTop.dy = vMax_fy - vMid_fy;
   eBot.dx = vMid_fx - vMin_fx;
   eBot.dy = vMid_fy - vMin_fy;
#else
   eMaj.dx = FixedToFloat(vMax_fx - vMin_fx);
   eMaj.dy = FixedToFloat(vMax_fy - vMin_fy);
   eTop.dx = FixedToFloat(vMax_fx - vMid_fx);
   eTop.dy = FixedToFloat(vMax_fy - vMid_fy);
   eBot.dx = FixedToFloat(vMid_fx - vMin_fx);
   eBot.dy = FixedToFloat(vMid_fy - vMin_fy);
#endif

   /* compute area, oneOverArea and perform backface culling */
   {
#if TRIANGLE_WALK_DOUBLE
      const GLdouble area = eMaj.dx * eBot.dy - eBot.dx * eMaj.dy;
#else
      const GLfloat area = eMaj.dx * eBot.dy - eBot.dx * eMaj.dy;
#endif
      /* Do backface culling */
      if (area * bf < 0.0)
         return;

      if (IS_INF_OR_NAN(area) || area == 0.0F)
         return;

      oneOverArea = 1.0F / area;
   }


   span.facing = ctx->_Facing; /* for 2-sided stencil test */

   /* Edge setup.  For a triangle strip these could be reused... */
   {