s_tritemp.h

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

       */
#ifdef SETUP_CODE
      SETUP_CODE
#endif

      scan_from_left_to_right = (oneOverArea < 0.0F);


      /* compute d?/dx and d?/dy derivatives */
#ifdef INTERP_Z
      span.interpMask |= SPAN_Z;
      {
         GLfloat eMaj_dz = vMax->attrib[FRAG_ATTRIB_WPOS][2] - vMin->attrib[FRAG_ATTRIB_WPOS][2];
         GLfloat eBot_dz = vMid->attrib[FRAG_ATTRIB_WPOS][2] - vMin->attrib[FRAG_ATTRIB_WPOS][2];
         span.attrStepX[FRAG_ATTRIB_WPOS][2] = oneOverArea * (eMaj_dz * eBot.dy - eMaj.dy * eBot_dz);
         if (span.attrStepX[FRAG_ATTRIB_WPOS][2] > maxDepth ||
             span.attrStepX[FRAG_ATTRIB_WPOS][2] < -maxDepth) {
            /* probably a sliver triangle */
            span.attrStepX[FRAG_ATTRIB_WPOS][2] = 0.0;
            span.attrStepY[FRAG_ATTRIB_WPOS][2] = 0.0;
         }
         else {
            span.attrStepY[FRAG_ATTRIB_WPOS][2] = oneOverArea * (eMaj.dx * eBot_dz - eMaj_dz * eBot.dx);
         }
         if (depthBits <= 16)
            span.zStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_WPOS][2]);
         else
            span.zStep = (GLint) span.attrStepX[FRAG_ATTRIB_WPOS][2];
      }
#endif
#ifdef INTERP_RGB
      span.interpMask |= SPAN_RGBA;
      if (ctx->Light.ShadeModel == GL_SMOOTH) {
         GLfloat eMaj_dr = (GLfloat) (vMax->color[RCOMP] - vMin->color[RCOMP]);
         GLfloat eBot_dr = (GLfloat) (vMid->color[RCOMP] - vMin->color[RCOMP]);
         GLfloat eMaj_dg = (GLfloat) (vMax->color[GCOMP] - vMin->color[GCOMP]);
         GLfloat eBot_dg = (GLfloat) (vMid->color[GCOMP] - vMin->color[GCOMP]);
         GLfloat eMaj_db = (GLfloat) (vMax->color[BCOMP] - vMin->color[BCOMP]);
         GLfloat eBot_db = (GLfloat) (vMid->color[BCOMP] - vMin->color[BCOMP]);
#  ifdef INTERP_ALPHA
         GLfloat eMaj_da = (GLfloat) (vMax->color[ACOMP] - vMin->color[ACOMP]);
         GLfloat eBot_da = (GLfloat) (vMid->color[ACOMP] - vMin->color[ACOMP]);
#  endif
         span.attrStepX[FRAG_ATTRIB_COL0][0] = oneOverArea * (eMaj_dr * eBot.dy - eMaj.dy * eBot_dr);
         span.attrStepY[FRAG_ATTRIB_COL0][0] = oneOverArea * (eMaj.dx * eBot_dr - eMaj_dr * eBot.dx);
         span.attrStepX[FRAG_ATTRIB_COL0][1] = oneOverArea * (eMaj_dg * eBot.dy - eMaj.dy * eBot_dg);
         span.attrStepY[FRAG_ATTRIB_COL0][1] = oneOverArea * (eMaj.dx * eBot_dg - eMaj_dg * eBot.dx);
         span.attrStepX[FRAG_ATTRIB_COL0][2] = oneOverArea * (eMaj_db * eBot.dy - eMaj.dy * eBot_db);
         span.attrStepY[FRAG_ATTRIB_COL0][2] = oneOverArea * (eMaj.dx * eBot_db - eMaj_db * eBot.dx);
         span.redStep   = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][0]);
         span.greenStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][1]);
         span.blueStep  = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][2]);
#  ifdef INTERP_ALPHA
         span.attrStepX[FRAG_ATTRIB_COL0][3] = oneOverArea * (eMaj_da * eBot.dy - eMaj.dy * eBot_da);
         span.attrStepY[FRAG_ATTRIB_COL0][3] = oneOverArea * (eMaj.dx * eBot_da - eMaj_da * eBot.dx);
         span.alphaStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][3]);
#  endif /* INTERP_ALPHA */
      }
      else {
         ASSERT(ctx->Light.ShadeModel == GL_FLAT);
         span.interpMask |= SPAN_FLAT;
         span.attrStepX[FRAG_ATTRIB_COL0][0] = span.attrStepY[FRAG_ATTRIB_COL0][0] = 0.0F;
         span.attrStepX[FRAG_ATTRIB_COL0][1] = span.attrStepY[FRAG_ATTRIB_COL0][1] = 0.0F;
         span.attrStepX[FRAG_ATTRIB_COL0][2] = span.attrStepY[FRAG_ATTRIB_COL0][2] = 0.0F;
	 span.redStep   = 0;
	 span.greenStep = 0;
	 span.blueStep  = 0;
#  ifdef INTERP_ALPHA
         span.attrStepX[FRAG_ATTRIB_COL0][3] = span.attrStepY[FRAG_ATTRIB_COL0][3] = 0.0F;
	 span.alphaStep = 0;
#  endif
      }
#endif /* INTERP_RGB */
#ifdef INTERP_INDEX
      span.interpMask |= SPAN_INDEX;
      if (ctx->Light.ShadeModel == GL_SMOOTH) {
         GLfloat eMaj_di = vMax->attrib[FRAG_ATTRIB_CI][0] - vMin->attrib[FRAG_ATTRIB_CI][0];
         GLfloat eBot_di = vMid->attrib[FRAG_ATTRIB_CI][0] - vMin->attrib[FRAG_ATTRIB_CI][0];
         didx = oneOverArea * (eMaj_di * eBot.dy - eMaj.dy * eBot_di);
         didy = oneOverArea * (eMaj.dx * eBot_di - eMaj_di * eBot.dx);
         span.indexStep = SignedFloatToFixed(didx);
      }
      else {
         span.interpMask |= SPAN_FLAT;
         didx = didy = 0.0F;
         span.indexStep = 0;
      }
#endif
#ifdef INTERP_INT_TEX
      {
         GLfloat eMaj_ds = (vMax->attrib[FRAG_ATTRIB_TEX0][0] - vMin->attrib[FRAG_ATTRIB_TEX0][0]) * S_SCALE;
         GLfloat eBot_ds = (vMid->attrib[FRAG_ATTRIB_TEX0][0] - vMin->attrib[FRAG_ATTRIB_TEX0][0]) * S_SCALE;
         GLfloat eMaj_dt = (vMax->attrib[FRAG_ATTRIB_TEX0][1] - vMin->attrib[FRAG_ATTRIB_TEX0][1]) * T_SCALE;
         GLfloat eBot_dt = (vMid->attrib[FRAG_ATTRIB_TEX0][1] - vMin->attrib[FRAG_ATTRIB_TEX0][1]) * T_SCALE;
         span.attrStepX[FRAG_ATTRIB_TEX0][0] = oneOverArea * (eMaj_ds * eBot.dy - eMaj.dy * eBot_ds);
         span.attrStepY[FRAG_ATTRIB_TEX0][0] = oneOverArea * (eMaj.dx * eBot_ds - eMaj_ds * eBot.dx);
         span.attrStepX[FRAG_ATTRIB_TEX0][1] = oneOverArea * (eMaj_dt * eBot.dy - eMaj.dy * eBot_dt);
         span.attrStepY[FRAG_ATTRIB_TEX0][1] = oneOverArea * (eMaj.dx * eBot_dt - eMaj_dt * eBot.dx);
         span.intTexStep[0] = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_TEX0][0]);
         span.intTexStep[1] = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_TEX0][1]);
      }
#endif
#ifdef INTERP_ATTRIBS
      {
         /* attrib[FRAG_ATTRIB_WPOS][3] is 1/W */
         const GLfloat wMax = vMax->attrib[FRAG_ATTRIB_WPOS][3];
         const GLfloat wMin = vMin->attrib[FRAG_ATTRIB_WPOS][3];
         const GLfloat wMid = vMid->attrib[FRAG_ATTRIB_WPOS][3];
         {
            const GLfloat eMaj_dw = wMax - wMin;
            const GLfloat eBot_dw = wMid - wMin;
            span.attrStepX[FRAG_ATTRIB_WPOS][3] = oneOverArea * (eMaj_dw * eBot.dy - eMaj.dy * eBot_dw);
            span.attrStepY[FRAG_ATTRIB_WPOS][3] = oneOverArea * (eMaj.dx * eBot_dw - eMaj_dw * eBot.dx);
         }
         ATTRIB_LOOP_BEGIN
            if (swrast->_InterpMode[attr] == GL_FLAT) {
               ASSIGN_4V(span.attrStepX[attr], 0.0, 0.0, 0.0, 0.0);
               ASSIGN_4V(span.attrStepY[attr], 0.0, 0.0, 0.0, 0.0);
            }
            else {
               GLuint c;
               for (c = 0; c < 4; c++) {
                  GLfloat eMaj_da = vMax->attrib[attr][c] * wMax - vMin->attrib[attr][c] * wMin;
                  GLfloat eBot_da = vMid->attrib[attr][c] * wMid - vMin->attrib[attr][c] * wMin;
                  span.attrStepX[attr][c] = oneOverArea * (eMaj_da * eBot.dy - eMaj.dy * eBot_da);
                  span.attrStepY[attr][c] = oneOverArea * (eMaj.dx * eBot_da - eMaj_da * eBot.dx);
               }
            }
         ATTRIB_LOOP_END
      }
#endif

      /*
       * We always sample at pixel centers.  However, we avoid
       * explicit half-pixel offsets in this code by incorporating
       * the proper offset in each of x and y during the
       * transformation to window coordinates.
       *
       * We also apply the usual rasterization rules to prevent
       * cracks and overlaps.  A pixel is considered inside a
       * subtriangle if it meets all of four conditions: it is on or
       * to the right of the left edge, strictly to the left of the
       * right edge, on or below the top edge, and strictly above
       * the bottom edge.  (Some edges may be degenerate.)
       *
       * The following discussion assumes left-to-right scanning
       * (that is, the major edge is on the left); the right-to-left
       * case is a straightforward variation.
       *
       * We start by finding the half-integral y coordinate that is
       * at or below the top of the triangle.  This gives us the
       * first scan line that could possibly contain pixels that are
       * inside the triangle.
       *
       * Next we creep down the major edge until we reach that y,
       * and compute the corresponding x coordinate on the edge.
       * Then we find the half-integral x that lies on or just
       * inside the edge.  This is the first pixel that might lie in
       * the interior of the triangle.  (We won't know for sure
       * until we check the other edges.)
       *
       * As we rasterize the triangle, we'll step down the major
       * edge.  For each step in y, we'll move an integer number
       * of steps in x.  There are two possible x step sizes, which
       * we'll call the ``inner'' step (guaranteed to land on the
       * edge or inside it) and the ``outer'' step (guaranteed to
       * land on the edge or outside it).  The inner and outer steps
       * differ by one.  During rasterization we maintain an error
       * term that indicates our distance from the true edge, and
       * select either the inner step or the outer step, whichever
       * gets us to the first pixel that falls inside the triangle.
       *
       * All parameters (z, red, etc.) as well as the buffer
       * addresses for color and z have inner and outer step values,
       * so that we can increment them appropriately.  This method
       * eliminates the need to adjust parameters by creeping a
       * sub-pixel amount into the triangle at each scanline.
       */

      {
         GLint subTriangle;
         GLfixed fxLeftEdge = 0, fxRightEdge = 0;
         GLfixed fdxLeftEdge = 0, fdxRightEdge = 0;
         GLfixed fError = 0, fdError = 0;
#ifdef PIXEL_ADDRESS
         PIXEL_TYPE *pRow = NULL;
         GLint dPRowOuter = 0, dPRowInner;  /* offset in bytes */
#endif
#ifdef INTERP_Z
#  ifdef DEPTH_TYPE
         struct gl_renderbuffer *zrb
            = ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
         DEPTH_TYPE *zRow = NULL;
         GLint dZRowOuter = 0, dZRowInner;  /* offset in bytes */
#  endif
         GLuint zLeft = 0;
         GLfixed fdzOuter = 0, fdzInner;
#endif
#ifdef INTERP_RGB
         GLint rLeft = 0, fdrOuter = 0, fdrInner;
         GLint gLeft = 0, fdgOuter = 0, fdgInner;
         GLint bLeft = 0, fdbOuter = 0, fdbInner;
#endif
#ifdef INTERP_ALPHA
         GLint aLeft = 0, fdaOuter = 0, fdaInner;
#endif
#ifdef INTERP_INDEX
         GLfixed iLeft=0, diOuter=0, diInner;
#endif
#ifdef INTERP_INT_TEX
         GLfixed sLeft=0, dsOuter=0, dsInner;
         GLfixed tLeft=0, dtOuter=0, dtInner;
#endif
#ifdef INTERP_ATTRIBS
         GLfloat wLeft = 0, dwOuter = 0, dwInner;
         GLfloat attrLeft[FRAG_ATTRIB_MAX][4];
         GLfloat daOuter[FRAG_ATTRIB_MAX][4], daInner[FRAG_ATTRIB_MAX][4];
#endif

         for (subTriangle=0; subTriangle<=1; subTriangle++) {
            EdgeT *eLeft, *eRight;
            int setupLeft, setupRight;
            int lines;

            if (subTriangle==0) {
               /* bottom half */
               if (scan_from_left_to_right) {
                  eLeft = &eMaj;
                  eRight = &eBot;
                  lines = eRight->lines;
                  setupLeft = 1;
                  setupRight = 1;
               }
               else {
                  eLeft = &eBot;
                  eRight = &eMaj;
                  lines = eLeft->lines;
                  setupLeft = 1;
                  setupRight = 1;
               }
            }
            else {
               /* top half */
               if (scan_from_left_to_right) {
                  eLeft = &eMaj;
                  eRight = &eTop;
                  lines = eRight->lines;
                  setupLeft = 0;
                  setupRight = 1;
               }
               else {
                  eLeft = &eTop;
                  eRight = &eMaj;
                  lines = eLeft->lines;
                  setupLeft = 1;
                  setupRight = 0;
               }
               if (lines == 0)
                  return;
            }

            if (setupLeft && eLeft->lines > 0) {
               const SWvertex *vLower = eLeft->v0;
               const GLfixed fsy = eLeft->fsy;
               const GLfixed fsx = eLeft->fsx;  /* no fractional part */
               const GLfixed fx = FixedCeil(fsx);  /* no fractional part */
               const GLfixed adjx = (GLfixed) (fx - eLeft->fx0); /* SCALED! */
               const GLfixed adjy = (GLfixed) eLeft->adjy;      /* SCALED! */
               GLint idxOuter;
               GLfloat dxOuter;
               GLfixed fdxOuter;

               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 = (GLfloat) idxOuter;
               span.y = FixedToInt(fsy);

               /* silence warnings on some compilers */
               (void) dxOuter;
               (void) adjx;
               (void) adjy;
               (void) vLower;

#ifdef PIXEL_ADDRESS
               {
                  pRow = (PIXEL_TYPE *) PIXEL_ADDRESS(FixedToInt(fxLeftEdge), span.y);
                  dPRowOuter = -((int)BYTES_PER_ROW) + idxOuter * sizeof(PIXEL_TYPE);
                  /* negative because Y=0 at bottom and increases upward */
               }
#endif
               /*
                * Now we need the set of parameter (z, color, etc.) values at
                * 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
                * the triangle, we shouldn't overflow or underflow for any
                * pixel that's actually inside the triangle.
                */

#ifdef INTERP_Z
               {
                  GLfloat z0 = vLower->attrib[FRAG_ATTRIB_WPOS][2];
                  if (depthBits <= 16) {
                     /* interpolate fixed-pt values */
                     GLfloat tmp = (z0 * FIXED_SCALE
                                    + span.attrStepX[FRAG_ATTRIB_WPOS][2] * adjx
                                    + span.attrStepY[FRAG_ATTRIB_WPOS][2] * adjy) + FIXED_HALF;
                     if (tmp < MAX_GLUINT / 2)
                        zLeft = (GLfixed) tmp;
                     else
                        zLeft = MAX_GLUINT / 2;
                     fdzOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_WPOS][2] +
                                                   dxOuter * span.attrStepX[FRAG_ATTRIB_WPOS][2]);
                  }
                  else {
                     /* interpolate depth values w/out scaling */
                     zLeft = (GLuint) (z0 + span.attrStepX[FRAG_ATTRIB_WPOS][2] * FixedToFloat(adjx)
                                          + span.attrStepY[FRAG_ATTRIB_WPOS][2] * FixedToFloat(adjy));
                     fdzOuter = (GLint) (span.attrStepY[FRAG_ATTRIB_WPOS][2] +
                                         dxOuter * span.attrStepX[FRAG_ATTRIB_WPOS][2]);
                  }
#  ifdef DEPTH_TYPE