src/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
  31 #include "main/glheader.h"
  32 #include "main/context.h"
  33 #include "main/colormac.h"
  34 #include "main/context.h"
  35 #include "main/macros.h"
  36 #include "main/imports.h"
  37 #include "s_aatriangle.h"
  38 #include "s_context.h"
  39 #include "s_span.h"
  40
  41
  42 /*
  43  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  44  * vertices and the given Z values.
  45  * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
  46  */
  47 static INLINE void
  48 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  49               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  50 {
  51    const GLfloat px = v1[0] - v0[0];
  52    const GLfloat py = v1[1] - v0[1];
  53    const GLfloat pz = z1 - z0;
  54
  55    const GLfloat qx = v2[0] - v0[0];
  56    const GLfloat qy = v2[1] - v0[1];
  57    const GLfloat qz = z2 - z0;
  58
  59    /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
  60    const GLfloat a = py * qz - pz * qy;
  61    const GLfloat b = pz * qx - px * qz;
  62    const GLfloat c = px * qy - py * qx;
  63    /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
  64       on the distance of plane from origin and arbitrary "w" parallel
  65       to the plane. */
  66    /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
  67       which is equal to "-d" below. */
  68    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  69
  70    plane[0] = a;
  71    plane[1] = b;
  72    plane[2] = c;
  73    plane[3] = d;
  74 }
  75
  76
  77 /*
  78  * Compute coefficients of a plane with a constant Z value.
  79  */
  80 static INLINE void
  81 constant_plane(GLfloat value, GLfloat plane[4])
  82 {
  83    plane[0] = 0.0;
  84    plane[1] = 0.0;
  85    plane[2] = -1.0;
  86    plane[3] = value;
  87 }
  88
  89 #define CONSTANT_PLANE(VALUE, PLANE)    \
  90 do {                                    \
  91    PLANE[0] = 0.0F;                     \
  92    PLANE[1] = 0.0F;                     \
  93    PLANE[2] = -1.0F;                    \
  94    PLANE[3] = VALUE;                    \
  95 } while (0)
  96
  97
  98
  99 /*
 100  * Solve plane equation for Z at (X,Y).
 101  */
 102 static INLINE GLfloat
 103 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 104 {
 105    ASSERT(plane[2] != 0.0F);
 106    return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 107 }
 108
 109
 110 #define SOLVE_PLANE(X, Y, PLANE) \
 111    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 112
 113
 114 /*
 115  * Return 1 / solve_plane().
 116  */
 117 static INLINE GLfloat
 118 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 119 {
 120    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 121    if (denom == 0.0F)
 122       return 0.0F;
 123    else
 124       return -plane[2] / denom;
 125 }
 126
 127
 128 /*
 129  * Solve plane and return clamped GLchan value.
 130  */
 131 static INLINE GLchan
 132 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 133 {
 134    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 135 #if CHAN_TYPE == GL_FLOAT
 136    return CLAMP(z, 0.0F, CHAN_MAXF);
 137 #else
 138    if (z < 0)
 139       return 0;
 140    else if (z > CHAN_MAX)
 141       return CHAN_MAX;
 142    return (GLchan) IROUND_POS(z);
 143 #endif
 144 }
 145
 146
 147 static INLINE GLfloat
 148 plane_dx(const GLfloat plane[4])
 149 {
 150    return -plane[0] / plane[2];
 151 }
 152
 153 static INLINE GLfloat
 154 plane_dy(const GLfloat plane[4])
 155 {
 156    return -plane[1] / plane[2];
 157 }
 158
 159
 160
 161 /*
 162  * Compute how much (area) of the given pixel is inside the triangle.
 163  * Vertices MUST be specified in counter-clockwise order.
 164  * Return:  coverage in [0, 1].
 165  */
 166 static GLfloat
 167 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 168                   const GLfloat v2[3], GLint winx, GLint winy)
 169 {
 170    /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
 171     * Contributed by Ray Tice.
 172     *
 173     * Jitter sample positions -
 174     * - average should be .5 in x & y for each column
 175     * - each of the 16 rows and columns should be used once
 176     * - the rectangle formed by the first four points
 177     *   should contain the other points
 178     * - the distrubition should be fairly even in any given direction
 179     *
 180     * The pattern drawn below isn't optimal, but it's better than a regular
 181     * grid.  In the drawing, the center of each subpixel is surrounded by
 182     * four dots.  The "x" marks the jittered position relative to the
 183     * subpixel center.
 184     */
 185 #define POS(a, b) (0.5+a*4+b)/16
 186    static const GLfloat samples[16][2] = {
 187       /* start with the four corners */
 188       { POS(0, 2), POS(0, 0) },
 189       { POS(3, 3), POS(0, 2) },
 190       { POS(0, 0), POS(3, 1) },
 191       { POS(3, 1), POS(3, 3) },
 192       /* continue with interior samples */
 193       { POS(1, 1), POS(0, 1) },
 194       { POS(2, 0), POS(0, 3) },
 195       { POS(0, 3), POS(1, 3) },
 196       { POS(1, 2), POS(1, 0) },
 197       { POS(2, 3), POS(1, 2) },
 198       { POS(3, 2), POS(1, 1) },
 199       { POS(0, 1), POS(2, 2) },
 200       { POS(1, 0), POS(2, 1) },
 201       { POS(2, 1), POS(2, 3) },
 202       { POS(3, 0), POS(2, 0) },
 203       { POS(1, 3), POS(3, 0) },
 204       { POS(2, 2), POS(3, 2) }
 205    };
 206
 207    const GLfloat x = (GLfloat) winx;
 208    const GLfloat y = (GLfloat) winy;
 209    const GLfloat dx0 = v1[0] - v0[0];
 210    const GLfloat dy0 = v1[1] - v0[1];
 211    const GLfloat dx1 = v2[0] - v1[0];
 212    const GLfloat dy1 = v2[1] - v1[1];
 213    const GLfloat dx2 = v0[0] - v2[0];
 214    const GLfloat dy2 = v0[1] - v2[1];
 215    GLint stop = 4, i;
 216    GLfloat insideCount = 16.0F;
 217
 218 #ifdef DEBUG
 219    {
 220       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 221       ASSERT(area >= 0.0);
 222    }
 223 #endif
 224
 225    for (i = 0; i < stop; i++) {
 226       const GLfloat sx = x + samples[i][0];
 227       const GLfloat sy = y + samples[i][1];
 228       /* cross product determines if sample is inside or outside each edge */
 229       GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0]));
 230       /* Check if the sample is exactly on an edge.  If so, let cross be a
 231        * positive or negative value depending on the direction of the edge.
 232        */
 233       if (cross == 0.0F)
 234          cross = dx0 + dy0;
 235       if (cross < 0.0F) {
 236          /* sample point is outside first edge */
 237          insideCount -= 1.0F;
 238          stop = 16;
 239       }
 240       else {
 241          /* sample point is inside first edge */
 242          cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0]));
 243          if (cross == 0.0F)
 244             cross = dx1 + dy1;
 245          if (cross < 0.0F) {
 246             /* sample point is outside second edge */
 247             insideCount -= 1.0F;
 248             stop = 16;
 249          }
 250          else {
 251             /* sample point is inside first and second edges */
 252             cross = (dx2 * (sy - v2[1]) -  dy2 * (sx - v2[0]));
 253             if (cross == 0.0F)
 254                cross = dx2 + dy2;
 255             if (cross < 0.0F) {
 256                /* sample point is outside third edge */
 257                insideCount -= 1.0F;
 258                stop = 16;
 259             }
 260          }
 261       }
 262    }
 263    if (stop == 4)
 264       return 1.0F;
 265    else
 266       return insideCount * (1.0F / 16.0F);
 267 }
 268
 269
 270
 271 /*
 272  * Compute how much (area) of the given pixel is inside the triangle.
 273  * Vertices MUST be specified in counter-clockwise order.
 274  * Return:  coverage in [0, 15].
 275  */
 276 static GLint
 277 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 278                   const GLfloat v2[3], GLint winx, GLint winy)
 279 {
 280    /* NOTE: 15 samples instead of 16. */
 281    static const GLfloat samples[15][2] = {
 282       /* start with the four corners */
 283       { POS(0, 2), POS(0, 0) },
 284       { POS(3, 3), POS(0, 2) },
 285       { POS(0, 0), POS(3, 1) },
 286       { POS(3, 1), POS(3, 3) },
 287       /* continue with interior samples */
 288       { POS(1, 1), POS(0, 1) },
 289       { POS(2, 0), POS(0, 3) },
 290       { POS(0, 3), POS(1, 3) },
 291       { POS(1, 2), POS(1, 0) },
 292       { POS(2, 3), POS(1, 2) },
 293       { POS(3, 2), POS(1, 1) },
 294       { POS(0, 1), POS(2, 2) },
 295       { POS(1, 0), POS(2, 1) },
 296       { POS(2, 1), POS(2, 3) },
 297       { POS(3, 0), POS(2, 0) },
 298       { POS(1, 3), POS(3, 0) }
 299    };
 300    const GLfloat x = (GLfloat) winx;
 301    const GLfloat y = (GLfloat) winy;
 302    const GLfloat dx0 = v1[0] - v0[0];
 303    const GLfloat dy0 = v1[1] - v0[1];
 304    const GLfloat dx1 = v2[0] - v1[0];
 305    const GLfloat dy1 = v2[1] - v1[1];
 306    const GLfloat dx2 = v0[0] - v2[0];
 307    const GLfloat dy2 = v0[1] - v2[1];
 308    GLint stop = 4, i;
 309    GLint insideCount = 15;
 310
 311 #ifdef DEBUG
 312    {
 313       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 314       ASSERT(area >= 0.0);
 315    }
 316 #endif
 317
 318    for (i = 0; i < stop; i++) {
 319       const GLfloat sx = x + samples[i][0];
 320       const GLfloat sy = y + samples[i][1];
 321       const GLfloat fx0 = sx - v0[0];
 322       const GLfloat fy0 = sy - v0[1];
 323       const GLfloat fx1 = sx - v1[0];
 324       const GLfloat fy1 = sy - v1[1];
 325       const GLfloat fx2 = sx - v2[0];
 326       const GLfloat fy2 = sy - v2[1];
 327       /* cross product determines if sample is inside or outside each edge */
 328       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 329       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 330       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 331       /* Check if the sample is exactly on an edge.  If so, let cross be a
 332        * positive or negative value depending on the direction of the edge.
 333        */
 334       if (cross0 == 0.0F)
 335          cross0 = dx0 + dy0;
 336       if (cross1 == 0.0F)
 337          cross1 = dx1 + dy1;
 338       if (cross2 == 0.0F)
 339          cross2 = dx2 + dy2;
 340       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 341          /* point is outside triangle */
 342          insideCount--;
 343          stop = 15;
 344       }
 345    }
 346    if (stop == 4)
 347       return 15;
 348    else
 349       return insideCount;
 350 }
 351
 352
 353 static void
 354 rgba_aa_tri(GLcontext *ctx,
 355             const SWvertex *v0,
 356             const SWvertex *v1,
 357             const SWvertex *v2)
 358 {
 359 #define DO_Z
 360 #define DO_RGBA
 361 #include "s_aatritemp.h"
 362 }
 363
 364
 365 static void
 366 index_aa_tri(GLcontext *ctx,
 367              const SWvertex *v0,
 368              const SWvertex *v1,
 369              const SWvertex *v2)
 370 {
 371 #define DO_Z
 372 #define DO_ATTRIBS
 373 #define DO_INDEX
 374 #include "s_aatritemp.h"
 375 }
 376
 377
 378 static void
 379 general_aa_tri(GLcontext *ctx,
 380                const SWvertex *v0,
 381                const SWvertex *v1,
 382                const SWvertex *v2)
 383 {
 384 #define DO_Z
 385 #define DO_RGBA
 386 #define DO_ATTRIBS
 387 #include "s_aatritemp.h"
 388 }
 389
 390
 391
 392 /*
 393  * Examine GL state and set swrast->Triangle to an
 394  * appropriate antialiased triangle rasterizer function.
 395  */
 396 void
 397 _swrast_set_aa_triangle_function(GLcontext *ctx)
 398 {
 399    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 400
 401    ASSERT(ctx->Polygon.SmoothFlag);
 402
 403    if (ctx->Texture._EnabledCoordUnits != 0
 404        || ctx->FragmentProgram._Current
 405        || swrast->_FogEnabled
 406        || NEED_SECONDARY_COLOR(ctx)) {
 407       SWRAST_CONTEXT(ctx)->Triangle = general_aa_tri;
 408    }
 409    else if (ctx->Visual.rgbMode) {
 410       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 411    }
 412    else {
 413       SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 414    }
 415
 416    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 417 }