dll/opengl/mesa/swrast/s_aatriangle.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5.3
   4  *
   5  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 /*
  27  * Antialiased Triangle rasterizers
  28  */
  29
  30 #include <precomp.h>
  31
  32 /*
  33  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  34  * vertices and the given Z values.
  35  * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
  36  */
  37 static inline void
  38 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  39               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  40 {
  41    const GLfloat px = v1[0] - v0[0];
  42    const GLfloat py = v1[1] - v0[1];
  43    const GLfloat pz = z1 - z0;
  44
  45    const GLfloat qx = v2[0] - v0[0];
  46    const GLfloat qy = v2[1] - v0[1];
  47    const GLfloat qz = z2 - z0;
  48
  49    /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
  50    const GLfloat a = py * qz - pz * qy;
  51    const GLfloat b = pz * qx - px * qz;
  52    const GLfloat c = px * qy - py * qx;
  53    /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
  54       on the distance of plane from origin and arbitrary "w" parallel
  55       to the plane. */
  56    /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
  57       which is equal to "-d" below. */
  58    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  59
  60    plane[0] = a;
  61    plane[1] = b;
  62    plane[2] = c;
  63    plane[3] = d;
  64 }
  65
  66
  67 /*
  68  * Compute coefficients of a plane with a constant Z value.
  69  */
  70 static inline void
  71 constant_plane(GLfloat value, GLfloat plane[4])
  72 {
  73    plane[0] = 0.0;
  74    plane[1] = 0.0;
  75    plane[2] = -1.0;
  76    plane[3] = value;
  77 }
  78
  79 #define CONSTANT_PLANE(VALUE, PLANE)    \
  80 do {                                    \
  81    PLANE[0] = 0.0F;                     \
  82    PLANE[1] = 0.0F;                     \
  83    PLANE[2] = -1.0F;                    \
  84    PLANE[3] = VALUE;                    \
  85 } while (0)
  86
  87
  88
  89 /*
  90  * Solve plane equation for Z at (X,Y).
  91  */
  92 static inline GLfloat
  93 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
  94 {
  95    ASSERT(plane[2] != 0.0F);
  96    return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
  97 }
  98
  99
 100 #define SOLVE_PLANE(X, Y, PLANE) \
 101    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 102
 103 /*
 104  * Solve plane and return clamped GLchan value.
 105  */
 106 static inline GLchan
 107 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 108 {
 109    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 110 #if CHAN_TYPE == GL_FLOAT
 111    return CLAMP(z, 0.0F, CHAN_MAXF);
 112 #else
 113    if (z < 0)
 114       return 0;
 115    else if (z > CHAN_MAX)
 116       return CHAN_MAX;
 117    return (GLchan) IROUND_POS(z);
 118 #endif
 119 }
 120
 121
 122 static inline GLfloat
 123 plane_dx(const GLfloat plane[4])
 124 {
 125    return -plane[0] / plane[2];
 126 }
 127
 128 static inline GLfloat
 129 plane_dy(const GLfloat plane[4])
 130 {
 131    return -plane[1] / plane[2];
 132 }
 133
 134
 135
 136 /*
 137  * Compute how much (area) of the given pixel is inside the triangle.
 138  * Vertices MUST be specified in counter-clockwise order.
 139  * Return:  coverage in [0, 1].
 140  */
 141 static GLfloat
 142 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 143                   const GLfloat v2[3], GLint winx, GLint winy)
 144 {
 145    /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
 146     * Contributed by Ray Tice.
 147     *
 148     * Jitter sample positions -
 149     * - average should be .5 in x & y for each column
 150     * - each of the 16 rows and columns should be used once
 151     * - the rectangle formed by the first four points
 152     *   should contain the other points
 153     * - the distrubition should be fairly even in any given direction
 154     *
 155     * The pattern drawn below isn't optimal, but it's better than a regular
 156     * grid.  In the drawing, the center of each subpixel is surrounded by
 157     * four dots.  The "x" marks the jittered position relative to the
 158     * subpixel center.
 159     */
 160 #define POS(a, b) (0.5+a*4+b)/16
 161    static const GLfloat samples[16][2] = {
 162       /* start with the four corners */
 163       { POS(0, 2), POS(0, 0) },
 164       { POS(3, 3), POS(0, 2) },
 165       { POS(0, 0), POS(3, 1) },
 166       { POS(3, 1), POS(3, 3) },
 167       /* continue with interior samples */
 168       { POS(1, 1), POS(0, 1) },
 169       { POS(2, 0), POS(0, 3) },
 170       { POS(0, 3), POS(1, 3) },
 171       { POS(1, 2), POS(1, 0) },
 172       { POS(2, 3), POS(1, 2) },
 173       { POS(3, 2), POS(1, 1) },
 174       { POS(0, 1), POS(2, 2) },
 175       { POS(1, 0), POS(2, 1) },
 176       { POS(2, 1), POS(2, 3) },
 177       { POS(3, 0), POS(2, 0) },
 178       { POS(1, 3), POS(3, 0) },
 179       { POS(2, 2), POS(3, 2) }
 180    };
 181
 182    const GLfloat x = (GLfloat) winx;
 183    const GLfloat y = (GLfloat) winy;
 184    const GLfloat dx0 = v1[0] - v0[0];
 185    const GLfloat dy0 = v1[1] - v0[1];
 186    const GLfloat dx1 = v2[0] - v1[0];
 187    const GLfloat dy1 = v2[1] - v1[1];
 188    const GLfloat dx2 = v0[0] - v2[0];
 189    const GLfloat dy2 = v0[1] - v2[1];
 190    GLint stop = 4, i;
 191    GLfloat insideCount = 16.0F;
 192
 193    ASSERT(dx0 * dy1 - dx1 * dy0 >= 0.0); /* area >= 0.0 */
 194
 195    for (i = 0; i < stop; i++) {
 196       const GLfloat sx = x + samples[i][0];
 197       const GLfloat sy = y + samples[i][1];
 198       /* cross product determines if sample is inside or outside each edge */
 199       GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0]));
 200       /* Check if the sample is exactly on an edge.  If so, let cross be a
 201        * positive or negative value depending on the direction of the edge.
 202        */
 203       if (cross == 0.0F)
 204          cross = dx0 + dy0;
 205       if (cross < 0.0F) {
 206          /* sample point is outside first edge */
 207          insideCount -= 1.0F;
 208          stop = 16;
 209       }
 210       else {
 211          /* sample point is inside first edge */
 212          cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0]));
 213          if (cross == 0.0F)
 214             cross = dx1 + dy1;
 215          if (cross < 0.0F) {
 216             /* sample point is outside second edge */
 217             insideCount -= 1.0F;
 218             stop = 16;
 219          }
 220          else {
 221             /* sample point is inside first and second edges */
 222             cross = (dx2 * (sy - v2[1]) -  dy2 * (sx - v2[0]));
 223             if (cross == 0.0F)
 224                cross = dx2 + dy2;
 225             if (cross < 0.0F) {
 226                /* sample point is outside third edge */
 227                insideCount -= 1.0F;
 228                stop = 16;
 229             }
 230          }
 231       }
 232    }
 233    if (stop == 4)
 234       return 1.0F;
 235    else
 236       return insideCount * (1.0F / 16.0F);
 237 }
 238
 239
 240
 241 static void
 242 rgba_aa_tri(struct gl_context *ctx,
 243             const SWvertex *v0,
 244             const SWvertex *v1,
 245             const SWvertex *v2)
 246 {
 247 #define DO_Z
 248 #include "s_aatritemp.h"
 249 }
 250
 251
 252 static void
 253 general_aa_tri(struct gl_context *ctx,
 254                const SWvertex *v0,
 255                const SWvertex *v1,
 256                const SWvertex *v2)
 257 {
 258 #define DO_Z
 259 #define DO_ATTRIBS
 260 #include "s_aatritemp.h"
 261 }
 262
 263
 264
 265 /*
 266  * Examine GL state and set swrast->Triangle to an
 267  * appropriate antialiased triangle rasterizer function.
 268  */
 269 void
 270 _swrast_set_aa_triangle_function(struct gl_context *ctx)
 271 {
 272    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 273
 274    ASSERT(ctx->Polygon.SmoothFlag);
 275
 276    if (ctx->Texture._EnabledCoord
 277        || swrast->_FogEnabled) {
 278       SWRAST_CONTEXT(ctx)->Triangle = general_aa_tri;
 279    }
 280    else {
 281       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 282    }
 283
 284    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 285 }