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/* $Id: s_aatriangle.c,v 1.1 2003-02-28 11:49:40 pj Exp $ */

/*

 * Mesa 3-D graphics library

 * Version:  4.1

 *

 * Copyright (C) 1999-2002  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.

 */

/*

 * Antialiased Triangle rasterizers

 */

#include "glheader.h"

#include "macros.h"

#include "imports.h"

#include "mmath.h"

#include "s_aatriangle.h"

#include "s_context.h"

#include "s_span.h"

/*

 * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2

 * vertices and the given Z values.

 * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.

 */

static INLINE void

compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],

              GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])

{

   const GLfloat px = v1[0] - v0[0];

   const GLfloat py = v1[1] - v0[1];

   const GLfloat pz = z1 - z0;

   const GLfloat qx = v2[0] - v0[0];

   const GLfloat qy = v2[1] - v0[1];

   const GLfloat qz = z2 - z0;

   /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */

   const GLfloat a = py * qz - pz * qy;

   const GLfloat b = pz * qx - px * qz;

   const GLfloat c = px * qy - py * qx;

   /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending

      on the distance of plane from origin and arbitrary "w" parallel

      to the plane. */

   /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",

      which is equal to "-d" below. */

   const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);

   plane[0] = a;

   plane[1] = b;

   plane[2] = c;

   plane[3] = d;

}

/*

 * Compute coefficients of a plane with a constant Z value.

 */

static INLINE void

constant_plane(GLfloat value, GLfloat plane[4])

{

   plane[0] = 0.0;

   plane[1] = 0.0;

   plane[2] = -1.0;

   plane[3] = value;

}

#define CONSTANT_PLANE(VALUE, PLANE)    \

do {                                    \

   PLANE[0] = 0.0F;                     \

   PLANE[1] = 0.0F;                     \

   PLANE[2] = -1.0F;                    \

   PLANE[3] = VALUE;                    \

} while (0)

/*

 * Solve plane equation for Z at (X,Y).

 */

static INLINE GLfloat

solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])

{

   ASSERT(plane[2] != 0.0F);

   return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];

}

#define SOLVE_PLANE(X, Y, PLANE) \

   ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])

/*

 * Return 1 / solve_plane().

 */

static INLINE GLfloat

solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])

{

   const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;

   if (denom == 0.0F)

      return 0.0F;

   else

      return -plane[2] / denom;

}

/*

 * Solve plane and return clamped GLchan value.

 */

static INLINE GLchan

solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])

{

   GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;

   if (z < 0.0F)

      return 0;

   else if (z > CHAN_MAXF)

      return (GLchan) CHAN_MAXF;

   return (GLchan) (GLint) z;

}

/*

 * Compute how much (area) of the given pixel is inside the triangle.

 * Vertices MUST be specified in counter-clockwise order.

 * Return:  coverage in [0, 1].

 */

static GLfloat

compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],

                  const GLfloat v2[3], GLint winx, GLint winy)

{

   /* Given a position [0,3]x[0,3] return the sub-pixel sample position.

    * Contributed by Ray Tice.

    *

    * Jitter sample positions -

    * - average should be .5 in x & y for each column

    * - each of the 16 rows and columns should be used once

    * - the rectangle formed by the first four points

    *   should contain the other points

    * - the distrubition should be fairly even in any given direction

    *

    * The pattern drawn below isn't optimal, but it's better than a regular

    * grid.  In the drawing, the center of each subpixel is surrounded by

    * four dots.  The "x" marks the jittered position relative to the

    * subpixel center.

    */

#define POS(a, b) (0.5+a*4+b)/16

   static const GLfloat samples[16][2] = {

      /* start with the four corners */

      { POS(0, 2), POS(0, 0) },

      { POS(3, 3), POS(0, 2) },

      { POS(0, 0), POS(3, 1) },

      { POS(3, 1), POS(3, 3) },

      /* continue with interior samples */

      { POS(1, 1), POS(0, 1) },

      { POS(2, 0), POS(0, 3) },

      { POS(0, 3), POS(1, 3) },

      { POS(1, 2), POS(1, 0) },

      { POS(2, 3), POS(1, 2) },

      { POS(3, 2), POS(1, 1) },

      { POS(0, 1), POS(2, 2) },

      { POS(1, 0), POS(2, 1) },

      { POS(2, 1), POS(2, 3) },

      { POS(3, 0), POS(2, 0) },

      { POS(1, 3), POS(3, 0) },

      { POS(2, 2), POS(3, 2) }

   };

   const GLfloat x = (GLfloat) winx;

   const GLfloat y = (GLfloat) winy;

   const GLfloat dx0 = v1[0] - v0[0];

   const GLfloat dy0 = v1[1] - v0[1];

   const GLfloat dx1 = v2[0] - v1[0];

   const GLfloat dy1 = v2[1] - v1[1];

   const GLfloat dx2 = v0[0] - v2[0];

   const GLfloat dy2 = v0[1] - v2[1];

   GLint stop = 4, i;

   GLfloat insideCount = 16.0F;

#ifdef 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 - v0[0];

      const GLfloat fy0 = sy - v0[1];

      const GLfloat fx1 = sx - v1[0];

      const GLfloat fy1 = sy - v1[1];

      const GLfloat fx2 = sx - v2[0];

      const GLfloat fy2 = sy - v2[1];

      /* cross product determines if sample is inside or outside each edge */

      GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);

      GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);

      GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);

      /* 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 = dx0 + dy0;

      if (cross1 == 0.0F)

         cross1 = dx1 + dy1;

      if (cross2 == 0.0F)

         cross2 = dx2 + dy2;

      if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {

         /* point is outside triangle */

         insideCount -= 1.0F;

         stop = 16;

      }

   }

   if (stop == 4)

      return 1.0F;

   else

      return insideCount * (1.0F / 16.0F);

}

/*

 * Compute how much (area) of the given pixel is inside the triangle.

 * Vertices MUST be specified in counter-clockwise order.

 * Return:  coverage in [0, 15].

 */

static GLint

compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],

                  const GLfloat v2[3], GLint winx, GLint winy)

{

   /* NOTE: 15 samples instead of 16. */

   static const GLfloat samples[15][2] = {

      /* start with the four corners */

      { POS(0, 2), POS(0, 0) },

      { POS(3, 3), POS(0, 2) },

      { POS(0, 0), POS(3, 1) },

      { POS(3, 1), POS(3, 3) },

      /* continue with interior samples */

      { POS(1, 1), POS(0, 1) },

      { POS(2, 0), POS(0, 3) },

      { POS(0, 3), POS(1, 3) },

      { POS(1, 2), POS(1, 0) },

      { POS(2, 3), POS(1, 2) },

      { POS(3, 2), POS(1, 1) },

      { POS(0, 1), POS(2, 2) },

      { POS(1, 0), POS(2, 1) },

      { POS(2, 1), POS(2, 3) },

      { POS(3, 0), POS(2, 0) },

      { POS(1, 3), POS(3, 0) }

   };

   const GLfloat x = (GLfloat) winx;

   const GLfloat y = (GLfloat) winy;

   const GLfloat dx0 = v1[0] - v0[0];

   const GLfloat dy0 = v1[1] - v0[1];

   const GLfloat dx1 = v2[0] - v1[0];

   const GLfloat dy1 = v2[1] - v1[1];

   const GLfloat dx2 = v0[0] - v2[0];

   const GLfloat dy2 = v0[1] - v2[1];

   GLint stop = 4, i;

   GLint insideCount = 15;

#ifdef 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 - v0[0];

      const GLfloat fy0 = sy - v0[1];

      const GLfloat fx1 = sx - v1[0];

      const GLfloat fy1 = sy - v1[1];

      const GLfloat fx2 = sx - v2[0];

      const GLfloat fy2 = sy - v2[1];

      /* cross product determines if sample is inside or outside each edge */

      GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);

      GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);

      GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);

      /* 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 = dx0 + dy0;

      if (cross1 == 0.0F)

         cross1 = dx1 + dy1;

      if (cross2 == 0.0F)

         cross2 = dx2 + dy2;

      if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {

         /* point is outside triangle */

         insideCount--;

         stop = 15;

      }

   }

   if (stop == 4)

      return 15;

   else

      return insideCount;

}

static void

rgba_aa_tri(GLcontext *ctx,

            const SWvertex *v0,

            const SWvertex *v1,

            const SWvertex *v2)

{

#define DO_Z

#define DO_FOG

#define DO_RGBA

#include "s_aatritemp.h"

}

static void

index_aa_tri(GLcontext *ctx,

             const SWvertex *v0,

             const SWvertex *v1,

             const SWvertex *v2)

{

#define DO_Z

#define DO_FOG

#define DO_INDEX

#include "s_aatritemp.h"

}

/*

 * Compute mipmap level of detail.

 * XXX we should really include the R coordinate in this computation

 * in order to do 3-D texture mipmapping.

 */

static INLINE GLfloat

compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],

               const GLfloat qPlane[4], GLfloat cx, GLfloat cy,

               GLfloat invQ, GLfloat texWidth, GLfloat texHeight)

{

   const GLfloat s = solve_plane(cx, cy, sPlane);

   const GLfloat t = solve_plane(cx, cy, tPlane);

   const GLfloat invQ_x1 = solve_plane_recip(cx+1.0F, cy, qPlane);

   const GLfloat invQ_y1 = solve_plane_recip(cx, cy+1.0F, qPlane);

   const GLfloat s_x1 = s - sPlane[0] / sPlane[2];

   const GLfloat s_y1 = s - sPlane[1] / sPlane[2];

   const GLfloat t_x1 = t - tPlane[0] / tPlane[2];

   const GLfloat t_y1 = t - tPlane[1] / tPlane[2];

   GLfloat dsdx = s_x1 * invQ_x1 - s * invQ;

   GLfloat dsdy = s_y1 * invQ_y1 - s * invQ;

   GLfloat dtdx = t_x1 * invQ_x1 - t * invQ;

   GLfloat dtdy = t_y1 * invQ_y1 - t * invQ;

   GLfloat maxU, maxV, rho, lambda;

   dsdx = FABSF(dsdx);

   dsdy = FABSF(dsdy);

   dtdx = FABSF(dtdx);

   dtdy = FABSF(dtdy);

   maxU = MAX2(dsdx, dsdy) * texWidth;

   maxV = MAX2(dtdx, dtdy) * texHeight;

   rho = MAX2(maxU, maxV);

   lambda = LOG2(rho);

   return lambda;

}

static void

tex_aa_tri(GLcontext *ctx,

           const SWvertex *v0,

           const SWvertex *v1,

           const SWvertex *v2)

{

#define DO_Z

#define DO_FOG

#define DO_RGBA

#define DO_TEX

#include "s_aatritemp.h"

}

static void

spec_tex_aa_tri(GLcontext *ctx,

                const SWvertex *v0,

                const SWvertex *v1,

                const SWvertex *v2)

{

#define DO_Z

#define DO_FOG

#define DO_RGBA

#define DO_TEX

#define DO_SPEC

#include "s_aatritemp.h"

}

static void

multitex_aa_tri(GLcontext *ctx,

                const SWvertex *v0,

                const SWvertex *v1,

                const SWvertex *v2)

{

#define DO_Z

#define DO_FOG

#define DO_RGBA

#define DO_MULTITEX

#include "s_aatritemp.h"

}

static void

spec_multitex_aa_tri(GLcontext *ctx,

                     const SWvertex *v0,

                     const SWvertex *v1,

                     const SWvertex *v2)

{

#define DO_Z

#define DO_FOG

#define DO_RGBA

#define DO_MULTITEX

#define DO_SPEC

#include "s_aatritemp.h"

}

/*

 * Examine GL state and set swrast->Triangle to an

 * appropriate antialiased triangle rasterizer function.

 */

void

_mesa_set_aa_triangle_function(GLcontext *ctx)

{

   ASSERT(ctx->Polygon.SmoothFlag);

   if (ctx->Texture._EnabledUnits != 0) {

      if (ctx->_TriangleCaps & DD_SEPARATE_SPECULAR) {

         if (ctx->Texture._EnabledUnits > 1) {

            SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;

         }

         else {

            SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;

         }

      }

      else {

         if (ctx->Texture._EnabledUnits > 1) {

            SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;

         }

         else {

            SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;

         }

      }

   }

   else if (ctx->Visual.rgbMode) {

      SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;

   }

   else {

      SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;

   }

   ASSERT(SWRAST_CONTEXT(ctx)->Triangle);

}