s_triangle.c

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/*
 * Mesa 3-D graphics library
 * Version:  7.3
 *
 * Copyright (C) 1999-2007  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.
 */


/*
 * When the device driver doesn't implement triangle rasterization it
 * can hook in _swrast_Triangle, which eventually calls one of these
 * functions to draw triangles.
 */

#include "main/glheader.h"
#include "main/context.h"
#include "main/colormac.h"
#include "main/imports.h"
#include "main/macros.h"
#include "main/texformat.h"

#include "s_aatriangle.h"
#include "s_context.h"
#include "s_feedback.h"
#include "s_span.h"
#include "s_triangle.h"


/*
 * Just used for feedback mode.
 */
GLboolean
_swrast_culltriangle( GLcontext *ctx,
                      const SWvertex *v0,
                      const SWvertex *v1,
                      const SWvertex *v2 )
{
   GLfloat ex = v1->attrib[FRAG_ATTRIB_WPOS][0] - v0->attrib[FRAG_ATTRIB_WPOS][0];
   GLfloat ey = v1->attrib[FRAG_ATTRIB_WPOS][1] - v0->attrib[FRAG_ATTRIB_WPOS][1];
   GLfloat fx = v2->attrib[FRAG_ATTRIB_WPOS][0] - v0->attrib[FRAG_ATTRIB_WPOS][0];
   GLfloat fy = v2->attrib[FRAG_ATTRIB_WPOS][1] - v0->attrib[FRAG_ATTRIB_WPOS][1];
   GLfloat c = ex*fy-ey*fx;

   if (c * SWRAST_CONTEXT(ctx)->_BackfaceCullSign > 0)
      return 0;

   return 1;
}



/*
 * Render a smooth or flat-shaded color index triangle.
 */
#define NAME ci_triangle
#define INTERP_Z 1
#define INTERP_ATTRIBS 1  /* just for fog */
#define INTERP_INDEX 1
#define RENDER_SPAN( span )  _swrast_write_index_span(ctx, &span);
#include "s_tritemp.h"



/*
 * Render a flat-shaded RGBA triangle.
 */
#define NAME flat_rgba_triangle
#define INTERP_Z 1
#define SETUP_CODE              \
   ASSERT(ctx->Texture._EnabledCoordUnits == 0);\
   ASSERT(ctx->Light.ShadeModel==GL_FLAT);  \
   span.interpMask |= SPAN_RGBA;        \
   span.red = ChanToFixed(v2->color[0]);    \
   span.green = ChanToFixed(v2->color[1]);  \
   span.blue = ChanToFixed(v2->color[2]);   \
   span.alpha = ChanToFixed(v2->color[3]);  \
   span.redStep = 0;                \
   span.greenStep = 0;              \
   span.blueStep = 0;               \
   span.alphaStep = 0;
#define RENDER_SPAN( span )  _swrast_write_rgba_span(ctx, &span);
#include "s_tritemp.h"



/*
 * Render a smooth-shaded RGBA triangle.
 */
#define NAME smooth_rgba_triangle
#define INTERP_Z 1
#define INTERP_RGB 1
#define INTERP_ALPHA 1
#define SETUP_CODE              \
   {                        \
      /* texturing must be off */       \
      ASSERT(ctx->Texture._EnabledCoordUnits == 0); \
      ASSERT(ctx->Light.ShadeModel==GL_SMOOTH); \
   }
#define RENDER_SPAN( span )  _swrast_write_rgba_span(ctx, &span);
#include "s_tritemp.h"



/*
 * Render an RGB, GL_DECAL, textured triangle.
 * Interpolate S,T only w/out mipmapping or perspective correction.
 *
 * No fog.  No depth testing.
 */
#define NAME simple_textured_triangle
#define INTERP_INT_TEX 1
#define S_SCALE twidth
#define T_SCALE theight

#define SETUP_CODE                          \
   struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[0];  \
   struct gl_texture_object *obj =                  \
      ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];        \
   const GLint b = obj->BaseLevel;                  \
   const GLfloat twidth = (GLfloat) obj->Image[0][b]->Width;        \
   const GLfloat theight = (GLfloat) obj->Image[0][b]->Height;      \
   const GLint twidth_log2 = obj->Image[0][b]->WidthLog2;       \
   const GLchan *texture = (const GLchan *) obj->Image[0][b]->Data; \
   const GLint smask = obj->Image[0][b]->Width - 1;         \
   const GLint tmask = obj->Image[0][b]->Height - 1;            \
   if (!rb || !texture) {                       \
      return;                               \
   }

#define RENDER_SPAN( span )                     \
   GLuint i;                                \
   GLchan rgb[MAX_WIDTH][3];                        \
   span.intTex[0] -= FIXED_HALF; /* off-by-one error? */        \
   span.intTex[1] -= FIXED_HALF;                    \
   for (i = 0; i < span.end; i++) {                 \
      GLint s = FixedToInt(span.intTex[0]) & smask;         \
      GLint t = FixedToInt(span.intTex[1]) & tmask;         \
      GLint pos = (t << twidth_log2) + s;               \
      pos = pos + pos + pos;  /* multiply by 3 */           \
      rgb[i][RCOMP] = texture[pos];                 \
      rgb[i][GCOMP] = texture[pos+1];                   \
      rgb[i][BCOMP] = texture[pos+2];                   \
      span.intTex[0] += span.intTexStep[0];             \
      span.intTex[1] += span.intTexStep[1];             \
   }                                    \
   rb->PutRowRGB(ctx, rb, span.end, span.x, span.y, rgb, NULL);

#include "s_tritemp.h"



/*
 * Render an RGB, GL_DECAL, textured triangle.
 * Interpolate S,T, GL_LESS depth test, w/out mipmapping or
 * perspective correction.
 * Depth buffer bits must be <= sizeof(DEFAULT_SOFTWARE_DEPTH_TYPE)
 *
 * No fog.
 */
#define NAME simple_z_textured_triangle
#define INTERP_Z 1
#define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
#define INTERP_INT_TEX 1
#define S_SCALE twidth
#define T_SCALE theight

#define SETUP_CODE                          \
   struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[0];  \
   struct gl_texture_object *obj =                  \
      ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];        \
   const GLint b = obj->BaseLevel;                  \
   const GLfloat twidth = (GLfloat) obj->Image[0][b]->Width;        \
   const GLfloat theight = (GLfloat) obj->Image[0][b]->Height;      \
   const GLint twidth_log2 = obj->Image[0][b]->WidthLog2;       \
   const GLchan *texture = (const GLchan *) obj->Image[0][b]->Data; \
   const GLint smask = obj->Image[0][b]->Width - 1;         \
   const GLint tmask = obj->Image[0][b]->Height - 1;            \
   if (!rb || !texture) {                       \
      return;                               \
   }

#define RENDER_SPAN( span )                     \
   GLuint i;                                    \
   GLchan rgb[MAX_WIDTH][3];                        \
   span.intTex[0] -= FIXED_HALF; /* off-by-one error? */        \
   span.intTex[1] -= FIXED_HALF;                    \
   for (i = 0; i < span.end; i++) {                 \
      const GLuint z = FixedToDepth(span.z);                \
      if (z < zRow[i]) {                        \
         GLint s = FixedToInt(span.intTex[0]) & smask;          \
         GLint t = FixedToInt(span.intTex[1]) & tmask;          \
         GLint pos = (t << twidth_log2) + s;                \
         pos = pos + pos + pos;  /* multiply by 3 */            \
         rgb[i][RCOMP] = texture[pos];                  \
         rgb[i][GCOMP] = texture[pos+1];                \
         rgb[i][BCOMP] = texture[pos+2];                \
         zRow[i] = z;                           \
         span.array->mask[i] = 1;                   \
      }                                 \
      else {                                \
         span.array->mask[i] = 0;                   \
      }                                 \
      span.intTex[0] += span.intTexStep[0];             \
      span.intTex[1] += span.intTexStep[1];             \
      span.z += span.zStep;                     \
   }                                    \
   rb->PutRowRGB(ctx, rb, span.end, span.x, span.y, rgb, span.array->mask);

#include "s_tritemp.h"


#if CHAN_TYPE != GL_FLOAT

struct affine_info
{
   GLenum filter;
   GLenum format;
   GLenum envmode;
   GLint smask, tmask;
   GLint twidth_log2;
   const GLchan *texture;
   GLfixed er, eg, eb, ea;
   GLint tbytesline, tsize;
};


static INLINE GLint
ilerp(GLint t, GLint a, GLint b)
{
   return a + ((t * (b - a)) >> FIXED_SHIFT);
}

static INLINE GLint
ilerp_2d(GLint ia, GLint ib, GLint v00, GLint v10, GLint v01, GLint v11)
{
   const GLint temp0 = ilerp(ia, v00, v10);
   const GLint temp1 = ilerp(ia, v01, v11);
   return ilerp(ib, temp0, temp1);
}


/* This function can handle GL_NEAREST or GL_LINEAR sampling of 2D RGB or RGBA
 * textures with GL_REPLACE, GL_MODULATE, GL_BLEND, GL_DECAL or GL_ADD
 * texture env modes.
 */
static INLINE void
affine_span(GLcontext *ctx, SWspan *span,
            struct affine_info *info)
{
   GLchan sample[4];  /* the filtered texture sample */
   const GLuint texEnableSave = ctx->Texture._EnabledUnits;

   /* Instead of defining a function for each mode, a test is done
    * between the outer and inner loops. This is to reduce code size
    * and complexity. Observe that an optimizing compiler kills
    * unused variables (for instance tf,sf,ti,si in case of GL_NEAREST).
    */

#define NEAREST_RGB         \
   sample[RCOMP] = tex00[RCOMP];    \
   sample[GCOMP] = tex00[GCOMP];    \
   sample[BCOMP] = tex00[BCOMP];    \
   sample[ACOMP] = CHAN_MAX

#define LINEAR_RGB                          \
   sample[RCOMP] = ilerp_2d(sf, tf, tex00[0], tex01[0], tex10[0], tex11[0]);\
   sample[GCOMP] = ilerp_2d(sf, tf, tex00[1], tex01[1], tex10[1], tex11[1]);\
   sample[BCOMP] = ilerp_2d(sf, tf, tex00[2], tex01[2], tex10[2], tex11[2]);\
   sample[ACOMP] = CHAN_MAX;

#define NEAREST_RGBA  COPY_CHAN4(sample, tex00)

#define LINEAR_RGBA                         \
   sample[RCOMP] = ilerp_2d(sf, tf, tex00[0], tex01[0], tex10[0], tex11[0]);\
   sample[GCOMP] = ilerp_2d(sf, tf, tex00[1], tex01[1], tex10[1], tex11[1]);\
   sample[BCOMP] = ilerp_2d(sf, tf, tex00[2], tex01[2], tex10[2], tex11[2]);\
   sample[ACOMP] = ilerp_2d(sf, tf, tex00[3], tex01[3], tex10[3], tex11[3])

#define MODULATE                              \
   dest[RCOMP] = span->red   * (sample[RCOMP] + 1u) >> (FIXED_SHIFT + 8); \
   dest[GCOMP] = span->green * (sample[GCOMP] + 1u) >> (FIXED_SHIFT + 8); \
   dest[BCOMP] = span->blue  * (sample[BCOMP] + 1u) >> (FIXED_SHIFT + 8); \
   dest[ACOMP] = span->alpha * (sample[ACOMP] + 1u) >> (FIXED_SHIFT + 8)

#define DECAL                               \
   dest[RCOMP] = ((CHAN_MAX - sample[ACOMP]) * span->red +      \
               ((sample[ACOMP] + 1) * sample[RCOMP] << FIXED_SHIFT))    \
               >> (FIXED_SHIFT + 8);                    \
   dest[GCOMP] = ((CHAN_MAX - sample[ACOMP]) * span->green +        \
               ((sample[ACOMP] + 1) * sample[GCOMP] << FIXED_SHIFT))    \
               >> (FIXED_SHIFT + 8);                    \
   dest[BCOMP] = ((CHAN_MAX - sample[ACOMP]) * span->blue +     \
               ((sample[ACOMP] + 1) * sample[BCOMP] << FIXED_SHIFT))    \
               >> (FIXED_SHIFT + 8);                    \
   dest[ACOMP] = FixedToInt(span->alpha)

#define BLEND                               \
   dest[RCOMP] = ((CHAN_MAX - sample[RCOMP]) * span->red        \
               + (sample[RCOMP] + 1) * info->er) >> (FIXED_SHIFT + 8);  \
   dest[GCOMP] = ((CHAN_MAX - sample[GCOMP]) * span->green      \
               + (sample[GCOMP] + 1) * info->eg) >> (FIXED_SHIFT + 8);  \
   dest[BCOMP] = ((CHAN_MAX - sample[BCOMP]) * span->blue       \
               + (sample[BCOMP] + 1) * info->eb) >> (FIXED_SHIFT + 8);  \
   dest[ACOMP] = span->alpha * (sample[ACOMP] + 1) >> (FIXED_SHIFT + 8)

#define REPLACE  COPY_CHAN4(dest, sample)

#define ADD                             \
   {                                    \
      GLint rSum = FixedToInt(span->red)   + (GLint) sample[RCOMP]; \
      GLint gSum = FixedToInt(span->green) + (GLint) sample[GCOMP]; \
      GLint bSum = FixedToInt(span->blue)  + (GLint) sample[BCOMP]; \
      dest[RCOMP] = MIN2(rSum, CHAN_MAX);               \
      dest[GCOMP] = MIN2(gSum, CHAN_MAX);               \
      dest[BCOMP] = MIN2(bSum, CHAN_MAX);               \
      dest[ACOMP] = span->alpha * (sample[ACOMP] + 1) >> (FIXED_SHIFT + 8); \
  }

/* shortcuts */

#define NEAREST_RGB_REPLACE     \
   NEAREST_RGB;             \
   dest[0] = sample[0];         \
   dest[1] = sample[1];         \
   dest[2] = sample[2];         \
   dest[3] = FixedToInt(span->alpha);

#define NEAREST_RGBA_REPLACE  COPY_CHAN4(dest, tex00)

#define SPAN_NEAREST(DO_TEX, COMPS)                 \
    for (i = 0; i < span->end; i++) {               \
           /* Isn't it necessary to use FixedFloor below?? */       \
           GLint s = FixedToInt(span->intTex[0]) & info->smask;     \
           GLint t = FixedToInt(span->intTex[1]) & info->tmask;     \
           GLint pos = (t << info->twidth_log2) + s;            \
           const GLchan *tex00 = info->texture + COMPS * pos;       \
           DO_TEX;                          \
           span->red += span->redStep;                  \
       span->green += span->greenStep;              \
           span->blue += span->blueStep;                \
       span->alpha += span->alphaStep;              \
       span->intTex[0] += span->intTexStep[0];          \
       span->intTex[1] += span->intTexStep[1];          \
           dest += 4;                           \
    }

#define SPAN_LINEAR(DO_TEX, COMPS)                  \
    for (i = 0; i < span->end; i++) {               \
           /* Isn't it necessary to use FixedFloor below?? */       \
           const GLint s = FixedToInt(span->intTex[0]) & info->smask;   \
           const GLint t = FixedToInt(span->intTex[1]) & info->tmask;   \
           const GLfixed sf = span->intTex[0] & FIXED_FRAC_MASK;    \
           const GLfixed tf = span->intTex[1] & FIXED_FRAC_MASK;    \
           const GLint pos = (t << info->twidth_log2) + s;      \
           const GLchan *tex00 = info->texture + COMPS * pos;       \
           const GLchan *tex10 = tex00 + info->tbytesline;      \
           const GLchan *tex01 = tex00 + COMPS;             \
           const GLchan *tex11 = tex10 + COMPS;             \
           if (t == info->tmask) {                  \
              tex10 -= info->tsize;                 \
              tex11 -= info->tsize;                 \
           }                                \
           if (s == info->smask) {                  \
              tex01 -= info->tbytesline;                \
              tex11 -= info->tbytesline;                \
           }                                \
           DO_TEX;                          \
           span->red += span->redStep;                  \
       span->green += span->greenStep;              \
           span->blue += span->blueStep;                \
       span->alpha += span->alphaStep;              \
       span->intTex[0] += span->intTexStep[0];          \
       span->intTex[1] += span->intTexStep[1];          \
           dest += 4;                           \
    }


   GLuint i;
   GLchan *dest = span->array->rgba[0];

   /* Disable tex units so they're not re-applied in swrast_write_rgba_span */
   ctx->Texture._EnabledUnits = 0x0;

   span->intTex[0] -= FIXED_HALF;
   span->intTex[1] -= FIXED_HALF;
   switch (info->filter) {
   case GL_NEAREST:
      switch (info->format) {
      case GL_RGB:
         switch (info->envmode) {
         case GL_MODULATE:
            SPAN_NEAREST(NEAREST_RGB;MODULATE,3);
            break;
         case GL_DECAL:
         case GL_REPLACE:
            SPAN_NEAREST(NEAREST_RGB_REPLACE,3);
            break;
         case GL_BLEND:
            SPAN_NEAREST(NEAREST_RGB;BLEND,3);
            break;
         case GL_ADD:
            SPAN_NEAREST(NEAREST_RGB;ADD,3);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode in SPAN_LINEAR");
            return;
         }
         break;
      case GL_RGBA:
         switch(info->envmode) {
         case GL_MODULATE:
            SPAN_NEAREST(NEAREST_RGBA;MODULATE,4);
            break;
         case GL_DECAL:
            SPAN_NEAREST(NEAREST_RGBA;DECAL,4);
            break;
         case GL_BLEND:
            SPAN_NEAREST(NEAREST_RGBA;BLEND,4);
            break;
         case GL_ADD:
            SPAN_NEAREST(NEAREST_RGBA;ADD,4);
            break;
         case GL_REPLACE:
            SPAN_NEAREST(NEAREST_RGBA_REPLACE,4);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (2) in SPAN_LINEAR");
            return;
         }
         break;
      }
      break;

   case GL_LINEAR:
      span->intTex[0] -= FIXED_HALF;
      span->intTex[1] -= FIXED_HALF;
      switch (info->format) {
      case GL_RGB:
         switch (info->envmode) {
         case GL_MODULATE:
            SPAN_LINEAR(LINEAR_RGB;MODULATE,3);
            break;
         case GL_DECAL:
         case GL_REPLACE:
            SPAN_LINEAR(LINEAR_RGB;REPLACE,3);
            break;
         case GL_BLEND:
            SPAN_LINEAR(LINEAR_RGB;BLEND,3);
            break;
         case GL_ADD:
            SPAN_LINEAR(LINEAR_RGB;ADD,3);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (3) in SPAN_LINEAR");
            return;
         }
         break;
      case GL_RGBA:
         switch (info->envmode) {
         case GL_MODULATE:
            SPAN_LINEAR(LINEAR_RGBA;MODULATE,4);
            break;
         case GL_DECAL:
            SPAN_LINEAR(LINEAR_RGBA;DECAL,4);
            break;
         case GL_BLEND:
            SPAN_LINEAR(LINEAR_RGBA;BLEND,4);
            break;
         case GL_ADD:
            SPAN_LINEAR(LINEAR_RGBA;ADD,4);
            break;
         case GL_REPLACE:
            SPAN_LINEAR(LINEAR_RGBA;REPLACE,4);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (4) in SPAN_LINEAR");
            return;
         }
         break;
      }
      break;
   }
   span->interpMask &= ~SPAN_RGBA;
   ASSERT(span->arrayMask & SPAN_RGBA);

   _swrast_write_rgba_span(ctx, span);

   /* re-enable texture units */
   ctx->Texture._EnabledUnits = texEnableSave;

#undef SPAN_NEAREST
#undef SPAN_LINEAR
}



/*
 * Render an RGB/RGBA textured triangle without perspective correction.
 */
#define NAME affine_textured_triangle
#define INTERP_Z 1
#define INTERP_RGB 1
#define INTERP_ALPHA 1
#define INTERP_INT_TEX 1
#define S_SCALE twidth
#define T_SCALE theight

#define SETUP_CODE                          \
   struct affine_info info;                     \
   struct gl_texture_unit *unit = ctx->Texture.Unit+0;          \
   struct gl_texture_object *obj =                  \
      ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];        \
   const GLint b = obj->BaseLevel;                  \
   const GLfloat twidth = (GLfloat) obj->Image[0][b]->Width;        \
   const GLfloat theight = (GLfloat) obj->Image[0][b]->Height;      \
   info.texture = (const GLchan *) obj->Image[0][b]->Data;      \
   info.twidth_log2 = obj->Image[0][b]->WidthLog2;          \
   info.smask = obj->Image[0][b]->Width - 1;                \
   info.tmask = obj->Image[0][b]->Height - 1;               \
   info.format = obj->Image[0][b]->_BaseFormat;             \
   info.filter = obj->MinFilter;                    \
   info.envmode = unit->EnvMode;                    \
   span.arrayMask |= SPAN_RGBA;                     \
                                    \
   if (info.envmode == GL_BLEND) {                  \
      /* potential off-by-one error here? (1.0f -> 2048 -> 0) */    \
      info.er = FloatToFixed(unit->EnvColor[RCOMP] * CHAN_MAXF);    \
      info.eg = FloatToFixed(unit->EnvColor[GCOMP] * CHAN_MAXF);    \
      info.eb = FloatToFixed(unit->EnvColor[BCOMP] * CHAN_MAXF);    \
      info.ea = FloatToFixed(unit->EnvColor[ACOMP] * CHAN_MAXF);    \
   }                                    \
   if (!info.texture) {                         \
      /* this shouldn't happen */                   \
      return;                               \
   }                                    \
                                    \
   switch (info.format) {                       \
   case GL_ALPHA:                           \
   case GL_LUMINANCE:                           \
   case GL_INTENSITY:                           \
      info.tbytesline = obj->Image[0][b]->Width;            \
      break;                                \
   case GL_LUMINANCE_ALPHA:                     \
      info.tbytesline = obj->Image[0][b]->Width * 2;            \
      break;                                \
   case GL_RGB:                             \
      info.tbytesline = obj->Image[0][b]->Width * 3;            \
      break;                                \
   case GL_RGBA:                            \
      info.tbytesline = obj->Image[0][b]->Width * 4;            \
      break;                                \
   default:                             \
      _mesa_problem(NULL, "Bad texture format in affine_texture_triangle");\
      return;                               \
   }                                    \
   info.tsize = obj->Image[0][b]->Height * info.tbytesline;

#define RENDER_SPAN( span )   affine_span(ctx, &span, &info);

#include "s_tritemp.h"



struct persp_info
{
   GLenum filter;
   GLenum format;
   GLenum envmode;
   GLint smask, tmask;
   GLint twidth_log2;
   const GLchan *texture;
   GLfixed er, eg, eb, ea;   /* texture env color */
   GLint tbytesline, tsize;
};


static INLINE void
fast_persp_span(GLcontext *ctx, SWspan *span,
        struct persp_info *info)
{
   GLchan sample[4];  /* the filtered texture sample */

  /* Instead of defining a function for each mode, a test is done
   * between the outer and inner loops. This is to reduce code size
   * and complexity. Observe that an optimizing compiler kills
   * unused variables (for instance tf,sf,ti,si in case of GL_NEAREST).
   */
#define SPAN_NEAREST(DO_TEX,COMP)                   \
    for (i = 0; i < span->end; i++) {               \
           GLdouble invQ = tex_coord[2] ?               \
                                 (1.0 / tex_coord[2]) : 1.0;            \
           GLfloat s_tmp = (GLfloat) (tex_coord[0] * invQ);     \
           GLfloat t_tmp = (GLfloat) (tex_coord[1] * invQ);     \
           GLint s = IFLOOR(s_tmp) & info->smask;               \
           GLint t = IFLOOR(t_tmp) & info->tmask;               \
           GLint pos = (t << info->twidth_log2) + s;            \
           const GLchan *tex00 = info->texture + COMP * pos;        \
           DO_TEX;                          \
           span->red += span->redStep;                  \
       span->green += span->greenStep;              \
           span->blue += span->blueStep;                \
       span->alpha += span->alphaStep;              \
       tex_coord[0] += tex_step[0];                 \
       tex_coord[1] += tex_step[1];                 \
       tex_coord[2] += tex_step[2];                 \
           dest += 4;                           \
    }

#define SPAN_LINEAR(DO_TEX,COMP)                    \
    for (i = 0; i < span->end; i++) {               \
           GLdouble invQ = tex_coord[2] ?               \
                                 (1.0 / tex_coord[2]) : 1.0;            \
           const GLfloat s_tmp = (GLfloat) (tex_coord[0] * invQ);   \
           const GLfloat t_tmp = (GLfloat) (tex_coord[1] * invQ);   \
           const GLfixed s_fix = FloatToFixed(s_tmp) - FIXED_HALF;  \
           const GLfixed t_fix = FloatToFixed(t_tmp) - FIXED_HALF;      \
           const GLint s = FixedToInt(FixedFloor(s_fix)) & info->smask; \
           const GLint t = FixedToInt(FixedFloor(t_fix)) & info->tmask; \
           const GLfixed sf = s_fix & FIXED_FRAC_MASK;          \
           const GLfixed tf = t_fix & FIXED_FRAC_MASK;          \
           const GLint pos = (t << info->twidth_log2) + s;      \
           const GLchan *tex00 = info->texture + COMP * pos;        \
           const GLchan *tex10 = tex00 + info->tbytesline;      \
           const GLchan *tex01 = tex00 + COMP;              \
           const GLchan *tex11 = tex10 + COMP;              \
           if (t == info->tmask) {                  \
              tex10 -= info->tsize;                 \
              tex11 -= info->tsize;                 \
           }                                \
           if (s == info->smask) {                  \
              tex01 -= info->tbytesline;                \
              tex11 -= info->tbytesline;                \
           }                                \
           DO_TEX;                          \
           span->red   += span->redStep;                \
       span->green += span->greenStep;              \
           span->blue  += span->blueStep;               \
       span->alpha += span->alphaStep;              \
       tex_coord[0] += tex_step[0];                 \
       tex_coord[1] += tex_step[1];                 \
       tex_coord[2] += tex_step[2];                 \
           dest += 4;                           \
    }

   GLuint i;
   GLfloat tex_coord[3], tex_step[3];
   GLchan *dest = span->array->rgba[0];

   const GLuint savedTexEnable = ctx->Texture._EnabledUnits;
   ctx->Texture._EnabledUnits = 0;

   tex_coord[0] = span->attrStart[FRAG_ATTRIB_TEX0][0]  * (info->smask + 1);
   tex_step[0] = span->attrStepX[FRAG_ATTRIB_TEX0][0] * (info->smask + 1);
   tex_coord[1] = span->attrStart[FRAG_ATTRIB_TEX0][1] * (info->tmask + 1);
   tex_step[1] = span->attrStepX[FRAG_ATTRIB_TEX0][1] * (info->tmask + 1);
   /* span->attrStart[FRAG_ATTRIB_TEX0][2] only if 3D-texturing, here only 2D */
   tex_coord[2] = span->attrStart[FRAG_ATTRIB_TEX0][3];
   tex_step[2] = span->attrStepX[FRAG_ATTRIB_TEX0][3];

   switch (info->filter) {
   case GL_NEAREST:
      switch (info->format) {
      case GL_RGB:
         switch (info->envmode) {
         case GL_MODULATE:
            SPAN_NEAREST(NEAREST_RGB;MODULATE,3);
            break;
         case GL_DECAL:
         case GL_REPLACE:
            SPAN_NEAREST(NEAREST_RGB_REPLACE,3);
            break;
         case GL_BLEND:
            SPAN_NEAREST(NEAREST_RGB;BLEND,3);
            break;
         case GL_ADD:
            SPAN_NEAREST(NEAREST_RGB;ADD,3);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (5) in SPAN_LINEAR");
            return;
         }
         break;
      case GL_RGBA:
         switch(info->envmode) {
         case GL_MODULATE:
            SPAN_NEAREST(NEAREST_RGBA;MODULATE,4);
            break;
         case GL_DECAL:
            SPAN_NEAREST(NEAREST_RGBA;DECAL,4);
            break;
         case GL_BLEND:
            SPAN_NEAREST(NEAREST_RGBA;BLEND,4);
            break;
         case GL_ADD:
            SPAN_NEAREST(NEAREST_RGBA;ADD,4);
            break;
         case GL_REPLACE:
            SPAN_NEAREST(NEAREST_RGBA_REPLACE,4);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (6) in SPAN_LINEAR");
            return;
         }
         break;
      }
      break;

   case GL_LINEAR:
      switch (info->format) {
      case GL_RGB:
         switch (info->envmode) {
         case GL_MODULATE:
            SPAN_LINEAR(LINEAR_RGB;MODULATE,3);
            break;
         case GL_DECAL:
         case GL_REPLACE:
            SPAN_LINEAR(LINEAR_RGB;REPLACE,3);
            break;
         case GL_BLEND:
            SPAN_LINEAR(LINEAR_RGB;BLEND,3);
            break;
         case GL_ADD:
            SPAN_LINEAR(LINEAR_RGB;ADD,3);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (7) in SPAN_LINEAR");
            return;
         }
         break;
      case GL_RGBA:
         switch (info->envmode) {
         case GL_MODULATE:
            SPAN_LINEAR(LINEAR_RGBA;MODULATE,4);
            break;
         case GL_DECAL:
            SPAN_LINEAR(LINEAR_RGBA;DECAL,4);
            break;
         case GL_BLEND:
            SPAN_LINEAR(LINEAR_RGBA;BLEND,4);
            break;
         case GL_ADD:
            SPAN_LINEAR(LINEAR_RGBA;ADD,4);
            break;
         case GL_REPLACE:
            SPAN_LINEAR(LINEAR_RGBA;REPLACE,4);
            break;
         default:
            _mesa_problem(ctx, "bad tex env mode (8) in SPAN_LINEAR");
            return;
         }
         break;
      }
      break;
   }
   
   ASSERT(span->arrayMask & SPAN_RGBA);
   _swrast_write_rgba_span(ctx, span);

#undef SPAN_NEAREST
#undef SPAN_LINEAR

   /* restore state */
   ctx->Texture._EnabledUnits = savedTexEnable;
}


/*
 * Render an perspective corrected RGB/RGBA textured triangle.
 * The Q (aka V in Mesa) coordinate must be zero such that the divide
 * by interpolated Q/W comes out right.
 *
 */
#define NAME persp_textured_triangle
#define INTERP_Z 1
#define INTERP_RGB 1
#define INTERP_ALPHA 1
#define INTERP_ATTRIBS 1

#define SETUP_CODE                          \
   struct persp_info info;                      \
   const struct gl_texture_unit *unit = ctx->Texture.Unit+0;        \
   struct gl_texture_object *obj =                  \
      ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];        \
   const GLint b = obj->BaseLevel;                  \
   info.texture = (const GLchan *) obj->Image[0][b]->Data;      \
   info.twidth_log2 = obj->Image[0][b]->WidthLog2;          \
   info.smask = obj->Image[0][b]->Width - 1;                \
   info.tmask = obj->Image[0][b]->Height - 1;               \
   info.format = obj->Image[0][b]->_BaseFormat;             \
   info.filter = obj->MinFilter;                    \
   info.envmode = unit->EnvMode;                    \
                                    \
   if (info.envmode == GL_BLEND) {                  \
      /* potential off-by-one error here? (1.0f -> 2048 -> 0) */    \
      info.er = FloatToFixed(unit->EnvColor[RCOMP] * CHAN_MAXF);    \
      info.eg = FloatToFixed(unit->EnvColor[GCOMP] * CHAN_MAXF);    \
      info.eb = FloatToFixed(unit->EnvColor[BCOMP] * CHAN_MAXF);    \
      info.ea = FloatToFixed(unit->EnvColor[ACOMP] * CHAN_MAXF);    \
   }                                    \
   if (!info.texture) {                         \
      /* this shouldn't happen */                   \
      return;                               \
   }                                    \
                                    \
   switch (info.format) {                       \
   case GL_ALPHA:                           \
   case GL_LUMINANCE:                           \
   case GL_INTENSITY:                           \
      info.tbytesline = obj->Image[0][b]->Width;            \
      break;                                \
   case GL_LUMINANCE_ALPHA:                     \
      info.tbytesline = obj->Image[0][b]->Width * 2;            \
      break;                                \
   case GL_RGB:                             \
      info.tbytesline = obj->Image[0][b]->Width * 3;            \
      break;                                \
   case GL_RGBA:                            \
      info.tbytesline = obj->Image[0][b]->Width * 4;            \
      break;                                \
   default:                             \
      _mesa_problem(NULL, "Bad texture format in persp_textured_triangle");\
      return;                               \
   }                                    \
   info.tsize = obj->Image[0][b]->Height * info.tbytesline;

#define RENDER_SPAN( span )         \
   span.interpMask &= ~SPAN_RGBA;       \
   span.arrayMask |= SPAN_RGBA;         \
   fast_persp_span(ctx, &span, &info);

#include "s_tritemp.h"

#endif /*CHAN_TYPE != GL_FLOAT*/



/*
 * Render an RGBA triangle with arbitrary attributes.
 */
#define NAME general_triangle
#define INTERP_Z 1
#define INTERP_RGB 1
#define INTERP_ALPHA 1
#define INTERP_ATTRIBS 1
#define RENDER_SPAN( span )   _swrast_write_rgba_span(ctx, &span);
#include "s_tritemp.h"




/*
 * Special tri function for occlusion testing
 */
#define NAME occlusion_zless_triangle
#define INTERP_Z 1
#define SETUP_CODE                          \
   struct gl_renderbuffer *rb = ctx->DrawBuffer->_DepthBuffer;      \
   struct gl_query_object *q = ctx->Query.CurrentOcclusionObject;   \
   ASSERT(ctx->Depth.Test);                     \
   ASSERT(!ctx->Depth.Mask);                        \
   ASSERT(ctx->Depth.Func == GL_LESS);                  \
   if (!q) {                                \
      return;                               \
   }
#define RENDER_SPAN( span )                     \
   if (rb->DepthBits <= 16) {                       \
      GLuint i;                             \
      const GLushort *zRow = (const GLushort *)             \
         rb->GetPointer(ctx, rb, span.x, span.y);           \
      for (i = 0; i < span.end; i++) {                  \
         GLuint z = FixedToDepth(span.z);               \
         if (z < zRow[i]) {                     \
            q->Result++;                        \
         }                              \
         span.z += span.zStep;                      \
      }                                 \
   }                                    \
   else {                               \
      GLuint i;                             \
      const GLuint *zRow = (const GLuint *)             \
         rb->GetPointer(ctx, rb, span.x, span.y);           \
      for (i = 0; i < span.end; i++) {                  \
         if ((GLuint)span.z < zRow[i]) {                \
            q->Result++;                        \
         }                              \
         span.z += span.zStep;                      \
      }                                 \
   }
#include "s_tritemp.h"



static void
nodraw_triangle( GLcontext *ctx,
                 const SWvertex *v0,
                 const SWvertex *v1,
                 const SWvertex *v2 )
{
   (void) (ctx && v0 && v1 && v2);
}


/*
 * This is used when separate specular color is enabled, but not
 * texturing.  We add the specular color to the primary color,
 * draw the triangle, then restore the original primary color.
 * Inefficient, but seldom needed.
 */
void
_swrast_add_spec_terms_triangle(GLcontext *ctx, const SWvertex *v0,
                                const SWvertex *v1, const SWvertex *v2)
{
   SWvertex *ncv0 = (SWvertex *)v0; /* drop const qualifier */
   SWvertex *ncv1 = (SWvertex *)v1;
   SWvertex *ncv2 = (SWvertex *)v2;
   GLfloat rSum, gSum, bSum;
   GLchan cSave[3][4];

   /* save original colors */
   COPY_CHAN4( cSave[0], ncv0->color );
   COPY_CHAN4( cSave[1], ncv1->color );
   COPY_CHAN4( cSave[2], ncv2->color );
   /* sum v0 */
   rSum = CHAN_TO_FLOAT(ncv0->color[0]) + ncv0->attrib[FRAG_ATTRIB_COL1][0];
   gSum = CHAN_TO_FLOAT(ncv0->color[1]) + ncv0->attrib[FRAG_ATTRIB_COL1][1];
   bSum = CHAN_TO_FLOAT(ncv0->color[2]) + ncv0->attrib[FRAG_ATTRIB_COL1][2];
   UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[0], rSum);
   UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[1], gSum);
   UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[2], bSum);
   /* sum v1 */
   rSum = CHAN_TO_FLOAT(ncv1->color[0]) + ncv1->attrib[FRAG_ATTRIB_COL1][0];
   gSum = CHAN_TO_FLOAT(ncv1->color[1]) + ncv1->attrib[FRAG_ATTRIB_COL1][1];
   bSum = CHAN_TO_FLOAT(ncv1->color[2]) + ncv1->attrib[FRAG_ATTRIB_COL1][2];
   UNCLAMPED_FLOAT_TO_CHAN(ncv1->color[0], rSum);
   UNCLAMPED_FLOAT_TO_CHAN(ncv1->color[1], gSum);
   UNCLAMPED_FLOAT_TO_CHAN(ncv1->color[2], bSum);
   /* sum v2 */
   rSum = CHAN_TO_FLOAT(ncv2->color[0]) + ncv2->attrib[FRAG_ATTRIB_COL1][0];
   gSum = CHAN_TO_FLOAT(ncv2->color[1]) + ncv2->attrib[FRAG_ATTRIB_COL1][1];
   bSum = CHAN_TO_FLOAT(ncv2->color[2]) + ncv2->attrib[FRAG_ATTRIB_COL1][2];
   UNCLAMPED_FLOAT_TO_CHAN(ncv2->color[0], rSum);
   UNCLAMPED_FLOAT_TO_CHAN(ncv2->color[1], gSum);
   UNCLAMPED_FLOAT_TO_CHAN(ncv2->color[2], bSum);
   /* draw */
   SWRAST_CONTEXT(ctx)->SpecTriangle( ctx, ncv0, ncv1, ncv2 );
   /* restore original colors */
   COPY_CHAN4( ncv0->color, cSave[0] );
   COPY_CHAN4( ncv1->color, cSave[1] );
   COPY_CHAN4( ncv2->color, cSave[2] );
}



#ifdef DEBUG

/* record the current triangle function name */
const char *_mesa_triFuncName = NULL;

#define USE(triFunc)                \
do {                        \
    _mesa_triFuncName = #triFunc;       \
    /*printf("%s\n", _mesa_triFuncName);*/  \
    swrast->Triangle = triFunc;         \
} while (0)

#else

#define USE(triFunc)  swrast->Triangle = triFunc;

#endif




/*
 * Determine which triangle rendering function to use given the current
 * rendering context.
 *
 * Please update the summary flag _SWRAST_NEW_TRIANGLE if you add or
 * remove tests to this code.
 */
void
_swrast_choose_triangle( GLcontext *ctx )
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);
   const GLboolean rgbmode = ctx->Visual.rgbMode;

   if (ctx->Polygon.CullFlag &&
       ctx->Polygon.CullFaceMode == GL_FRONT_AND_BACK) {
      USE(nodraw_triangle);
      return;
   }

   if (ctx->RenderMode==GL_RENDER) {

      if (ctx->Polygon.SmoothFlag) {
         _swrast_set_aa_triangle_function(ctx);
         ASSERT(swrast->Triangle);
         return;
      }

      /* special case for occlusion testing */
      if (ctx->Query.CurrentOcclusionObject &&
          ctx->Depth.Test &&
          ctx->Depth.Mask == GL_FALSE &&
          ctx->Depth.Func == GL_LESS &&
          !ctx->Stencil.Enabled) {
         if ((rgbmode &&
              ctx->Color.ColorMask[0] == 0 &&
              ctx->Color.ColorMask[1] == 0 &&
              ctx->Color.ColorMask[2] == 0 &&
              ctx->Color.ColorMask[3] == 0)
             ||
             (!rgbmode && ctx->Color.IndexMask == 0)) {
            USE(occlusion_zless_triangle);
            return;
         }
      }

      if (!rgbmode) {
         USE(ci_triangle);
         return;
      }

      /*
       * XXX should examine swrast->_ActiveAttribMask to determine what
       * needs to be interpolated.
       */
      if (ctx->Texture._EnabledCoordUnits ||
          ctx->FragmentProgram._Current ||
          ctx->ATIFragmentShader._Enabled ||
          NEED_SECONDARY_COLOR(ctx) ||
          swrast->_FogEnabled) {
         /* Ugh, we do a _lot_ of tests to pick the best textured tri func */
         const struct gl_texture_object *texObj2D;
         const struct gl_texture_image *texImg;
         GLenum minFilter, magFilter, envMode;
         GLint format;
         texObj2D = ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];

         texImg = texObj2D ? texObj2D->Image[0][texObj2D->BaseLevel] : NULL;
         format = texImg ? texImg->TexFormat->MesaFormat : -1;
         minFilter = texObj2D ? texObj2D->MinFilter : (GLenum) 0;
         magFilter = texObj2D ? texObj2D->MagFilter : (GLenum) 0;
         envMode = ctx->Texture.Unit[0].EnvMode;

         /* First see if we can use an optimized 2-D texture function */
         if (ctx->Texture._EnabledCoordUnits == 0x1
             && !ctx->FragmentProgram._Current
             && !ctx->ATIFragmentShader._Enabled
             && ctx->Texture.Unit[0]._ReallyEnabled == TEXTURE_2D_BIT
             && texObj2D->WrapS == GL_REPEAT
             && texObj2D->WrapT == GL_REPEAT
             && texImg->_IsPowerOfTwo
             && texImg->Border == 0
             && texImg->Width == texImg->RowStride
             && (format == MESA_FORMAT_RGB || format == MESA_FORMAT_RGBA)
             && minFilter == magFilter
             && ctx->Light.Model.ColorControl == GL_SINGLE_COLOR
             && !swrast->_FogEnabled
             && ctx->Texture.Unit[0].EnvMode != GL_COMBINE_EXT) {
        if (ctx->Hint.PerspectiveCorrection==GL_FASTEST) {
           if (minFilter == GL_NEAREST
           && format == MESA_FORMAT_RGB
           && (envMode == GL_REPLACE || envMode == GL_DECAL)
           && ((swrast->_RasterMask == (DEPTH_BIT | TEXTURE_BIT)
            && ctx->Depth.Func == GL_LESS
            && ctx->Depth.Mask == GL_TRUE)
               || swrast->_RasterMask == TEXTURE_BIT)
           && ctx->Polygon.StippleFlag == GL_FALSE
                   && ctx->DrawBuffer->Visual.depthBits <= 16) {
          if (swrast->_RasterMask == (DEPTH_BIT | TEXTURE_BIT)) {
             USE(simple_z_textured_triangle);
          }
          else {
             USE(simple_textured_triangle);
          }
           }
           else {
#if CHAN_BITS != 8
                  USE(general_triangle);
#else
                  USE(affine_textured_triangle);
#endif
           }
        }
        else {
#if CHAN_BITS != 8
               USE(general_triangle);
#else
               USE(persp_textured_triangle);
#endif
        }
     }
         else {
            /* general case textured triangles */
            USE(general_triangle);
         }
      }
      else {
         ASSERT(!swrast->_FogEnabled);
         ASSERT(!NEED_SECONDARY_COLOR(ctx));
     if (ctx->Light.ShadeModel==GL_SMOOTH) {
        /* smooth shaded, no texturing, stippled or some raster ops */
#if CHAN_BITS != 8
               USE(general_triangle);
#else
               USE(smooth_rgba_triangle);
#endif
     }
     else {
        /* flat shaded, no texturing, stippled or some raster ops */
#if CHAN_BITS != 8
            USE(general_triangle);
#else
            USE(flat_rgba_triangle);
#endif
     }
      }
   }
   else if (ctx->RenderMode==GL_FEEDBACK) {
      USE(_swrast_feedback_triangle);
   }
   else {
      /* GL_SELECT mode */
      USE(_swrast_select_triangle);
   }
}