s_aaline.c

这是一个开放源代码的与WINNT/WIN2K/WIN2003兼容的操作系统

   GLint stop = 4, i;
   GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;

   if (!haveSamples) {
      make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
      haveSamples = GL_TRUE;
   }

#if 0 /*DEBUG*/
   {
      const GLfloat area = dx0 * dy1 - dx1 * dy0;
      assert(area >= 0.0);
   }
#endif

   for (i = 0; i < stop; i++) {
      const GLfloat sx = x + samples[i][0];
      const GLfloat sy = y + samples[i][1];
      const GLfloat fx0 = sx - info->qx0;
      const GLfloat fy0 = sy - info->qy0;
      const GLfloat fx1 = sx - info->qx1;
      const GLfloat fy1 = sy - info->qy1;
      const GLfloat fx2 = sx - info->qx2;
      const GLfloat fy2 = sy - info->qy2;
      const GLfloat fx3 = sx - info->qx3;
      const GLfloat fy3 = sy - info->qy3;
      /* cross product determines if sample is inside or outside each edge */
      GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
      GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
      GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
      GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
      /* Check if the sample is exactly on an edge.  If so, let cross be a
       * positive or negative value depending on the direction of the edge.
       */
      if (cross0 == 0.0F)
         cross0 = info->ex0 + info->ey0;
      if (cross1 == 0.0F)
         cross1 = info->ex1 + info->ey1;
      if (cross2 == 0.0F)
         cross2 = info->ex2 + info->ey2;
      if (cross3 == 0.0F)
         cross3 = info->ex3 + info->ey3;
      if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
         /* point is outside quadrilateral */
         insideCount -= 1.0F;
         stop = SUB_PIXEL * SUB_PIXEL;
      }
   }
   if (stop == 4)
      return 1.0F;
   else
      return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
}


/**
 * Compute coverage value for color index mode.
 * XXX this may not be quite correct.
 * \return coverage in [0,15].
 */
static GLfloat
compute_coveragei(const struct LineInfo *info,
                  GLint winx, GLint winy)
{
   return compute_coveragef(info, winx, winy) * 15.0F;
}



typedef void (*plot_func)(GLcontext *ctx, struct LineInfo *line,
                          int ix, int iy);
                         


/*
 * Draw an AA line segment (called many times per line when stippling)
 */
static void
segment(GLcontext *ctx,
        struct LineInfo *line,
        plot_func plot,
        GLfloat t0, GLfloat t1)
{
   const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
   const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
   /* compute the actual segment's endpoints */
   const GLfloat x0 = line->x0 + t0 * line->dx;
   const GLfloat y0 = line->y0 + t0 * line->dy;
   const GLfloat x1 = line->x0 + t1 * line->dx;
   const GLfloat y1 = line->y0 + t1 * line->dy;

   /* compute vertices of the line-aligned quadrilateral */
   line->qx0 = x0 - line->yAdj;
   line->qy0 = y0 + line->xAdj;
   line->qx1 = x0 + line->yAdj;
   line->qy1 = y0 - line->xAdj;
   line->qx2 = x1 + line->yAdj;
   line->qy2 = y1 - line->xAdj;
   line->qx3 = x1 - line->yAdj;
   line->qy3 = y1 + line->xAdj;
   /* compute the quad's edge vectors (for coverage calc) */
   line->ex0 = line->qx1 - line->qx0;
   line->ey0 = line->qy1 - line->qy0;
   line->ex1 = line->qx2 - line->qx1;
   line->ey1 = line->qy2 - line->qy1;
   line->ex2 = line->qx3 - line->qx2;
   line->ey2 = line->qy3 - line->qy2;
   line->ex3 = line->qx0 - line->qx3;
   line->ey3 = line->qy0 - line->qy3;

   if (absDx > absDy) {
      /* X-major line */
      GLfloat dydx = line->dy / line->dx;
      GLfloat xLeft, xRight, yBot, yTop;
      GLint ix, ixRight;
      if (x0 < x1) {
         xLeft = x0 - line->halfWidth;
         xRight = x1 + line->halfWidth;
         if (line->dy >= 0.0) {
            yBot = y0 - 3.0F * line->halfWidth;
            yTop = y0 + line->halfWidth;
         }
         else {
            yBot = y0 - line->halfWidth;
            yTop = y0 + 3.0F * line->halfWidth;
         }
      }
      else {
         xLeft = x1 - line->halfWidth;
         xRight = x0 + line->halfWidth;
         if (line->dy <= 0.0) {
            yBot = y1 - 3.0F * line->halfWidth;
            yTop = y1 + line->halfWidth;
         }
         else {
            yBot = y1 - line->halfWidth;
            yTop = y1 + 3.0F * line->halfWidth;
         }
      }

      /* scan along the line, left-to-right */
      ixRight = (GLint) (xRight + 1.0F);

      /*printf("avg span height: %g\n", yTop - yBot);*/
      for (ix = (GLint) xLeft; ix < ixRight; ix++) {
         const GLint iyBot = (GLint) yBot;
         const GLint iyTop = (GLint) (yTop + 1.0F);
         GLint iy;
         /* scan across the line, bottom-to-top */
         for (iy = iyBot; iy < iyTop; iy++) {
            (*plot)(ctx, line, ix, iy);
         }
         yBot += dydx;
         yTop += dydx;
      }
   }
   else {
      /* Y-major line */
      GLfloat dxdy = line->dx / line->dy;
      GLfloat yBot, yTop, xLeft, xRight;
      GLint iy, iyTop;
      if (y0 < y1) {
         yBot = y0 - line->halfWidth;
         yTop = y1 + line->halfWidth;
         if (line->dx >= 0.0) {
            xLeft = x0 - 3.0F * line->halfWidth;
            xRight = x0 + line->halfWidth;
         }
         else {
            xLeft = x0 - line->halfWidth;
            xRight = x0 + 3.0F * line->halfWidth;
         }
      }
      else {
         yBot = y1 - line->halfWidth;
         yTop = y0 + line->halfWidth;
         if (line->dx <= 0.0) {
            xLeft = x1 - 3.0F * line->halfWidth;
            xRight = x1 + line->halfWidth;
         }
         else {
            xLeft = x1 - line->halfWidth;
            xRight = x1 + 3.0F * line->halfWidth;
         }
      }

      /* scan along the line, bottom-to-top */
      iyTop = (GLint) (yTop + 1.0F);

      /*printf("avg span width: %g\n", xRight - xLeft);*/
      for (iy = (GLint) yBot; iy < iyTop; iy++) {
         const GLint ixLeft = (GLint) xLeft;
         const GLint ixRight = (GLint) (xRight + 1.0F);
         GLint ix;
         /* scan across the line, left-to-right */
         for (ix = ixLeft; ix < ixRight; ix++) {
            (*plot)(ctx, line, ix, iy);
         }
         xLeft += dxdy;
         xRight += dxdy;
      }
   }
}


#define NAME(x) aa_ci_##x
#define DO_Z
#define DO_FOG
#define DO_INDEX
#include "s_aalinetemp.h"


#define NAME(x) aa_rgba_##x
#define DO_Z
#define DO_FOG
#define DO_RGBA
#include "s_aalinetemp.h"


#define NAME(x)  aa_tex_rgba_##x
#define DO_Z
#define DO_FOG
#define DO_RGBA
#define DO_TEX
#include "s_aalinetemp.h"


#define NAME(x)  aa_multitex_rgba_##x
#define DO_Z
#define DO_FOG
#define DO_RGBA
#define DO_MULTITEX
#include "s_aalinetemp.h"


#define NAME(x)  aa_multitex_spec_##x
#define DO_Z
#define DO_FOG
#define DO_RGBA
#define DO_MULTITEX
#define DO_SPEC
#include "s_aalinetemp.h"



void
_swrast_choose_aa_line_function(GLcontext *ctx)
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);

   ASSERT(ctx->Line.SmoothFlag);

   if (ctx->Visual.rgbMode) {
      /* RGBA */
      if (ctx->Texture._EnabledCoordUnits != 0) {
         if (ctx->Texture._EnabledCoordUnits > 1) {
            /* Multitextured! */
            if (ctx->Light.Model.ColorControl==GL_SEPARATE_SPECULAR_COLOR || 
                ctx->Fog.ColorSumEnabled)
               swrast->Line = aa_multitex_spec_line;
            else
               swrast->Line = aa_multitex_rgba_line;
         }
         else {
            swrast->Line = aa_tex_rgba_line;
         }
      }
      else {
         swrast->Line = aa_rgba_line;
      }
   }
   else {
      /* Color Index */
      swrast->Line = aa_ci_line;
   }
}