src/mesa/swrast/s_aatriangle.c

   1 /* $Id: s_aatriangle.c,v 1.1 2000/10/31 18:00:04 keithw Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.5
   6  *
   7  * Copyright (C) 1999-2000  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 /*
  29  * Antialiased Triangle rasterizers
  30  */
  31
  32
  33 #include "s_aatriangle.h"
  34 #include "s_span.h"
  35
  36
  37 /*
  38  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  39  * vertices and the given Z values.
  40  */
  41 static INLINE void
  42 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  43               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  44 {
  45    const GLfloat px = v1[0] - v0[0];
  46    const GLfloat py = v1[1] - v0[1];
  47    const GLfloat pz = z1 - z0;
  48
  49    const GLfloat qx = v2[0] - v0[0];
  50    const GLfloat qy = v2[1] - v0[1];
  51    const GLfloat qz = z2 - z0;
  52
  53    const GLfloat a = py * qz - pz * qy;
  54    const GLfloat b = pz * qx - px * qz;
  55    const GLfloat c = px * qy - py * qx;
  56    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  57
  58    plane[0] = a;
  59    plane[1] = b;
  60    plane[2] = c;
  61    plane[3] = d;
  62 }
  63
  64
  65 /*
  66  * Compute coefficients of a plane with a constant Z value.
  67  */
  68 static INLINE void
  69 constant_plane(GLfloat value, GLfloat plane[4])
  70 {
  71    plane[0] = 0.0;
  72    plane[1] = 0.0;
  73    plane[2] = -1.0;
  74    plane[3] = value;
  75 }
  76
  77 #define CONSTANT_PLANE(VALUE, PLANE)    \
  78 do {                                    \
  79    PLANE[0] = 0.0F;                     \
  80    PLANE[1] = 0.0F;                     \
  81    PLANE[2] = -1.0F;                    \
  82    PLANE[3] = VALUE;                    \
  83 } while (0)
  84
  85
  86
  87 /*
  88  * Solve plane equation for Z at (X,Y).
  89  */
  90 static INLINE GLfloat
  91 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
  92 {
  93    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
  94    return z;
  95 }
  96
  97
  98 #define SOLVE_PLANE(X, Y, PLANE) \
  99    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 100
 101
 102 /*
 103  * Return 1 / solve_plane().
 104  */
 105 static INLINE GLfloat
 106 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 107 {
 108    GLfloat z = -plane[2] / (plane[3] + plane[0] * x + plane[1] * y);
 109    return z;
 110 }
 111
 112
 113
 114 /*
 115  * Solve plane and return clamped GLchan value.
 116  */
 117 static INLINE GLchan
 118 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 119 {
 120    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 121    if (z < 0.0F)
 122       return 0;
 123    else if (z > CHAN_MAXF)
 124       return CHAN_MAXF;
 125    return (GLchan) (GLint) z;
 126 }
 127
 128
 129
 130 /*
 131  * Compute how much (area) of the given pixel is inside the triangle.
 132  * Vertices MUST be specified in counter-clockwise order.
 133  * Return:  coverage in [0, 1].
 134  */
 135 static GLfloat
 136 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 137                   const GLfloat v2[3], GLint winx, GLint winy)
 138 {
 139    static const GLfloat samples[16][2] = {
 140       /* start with the four corners */
 141       { 0.00, 0.00 },
 142       { 0.75, 0.00 },
 143       { 0.00, 0.75 },
 144       { 0.75, 0.75 },
 145       /* continue with interior samples */
 146       { 0.25, 0.00 },
 147       { 0.50, 0.00 },
 148       { 0.00, 0.25 },
 149       { 0.25, 0.25 },
 150       { 0.50, 0.25 },
 151       { 0.75, 0.25 },
 152       { 0.00, 0.50 },
 153       { 0.25, 0.50 },
 154       { 0.50, 0.50 },
 155       { 0.75, 0.50 },
 156       { 0.25, 0.75 },
 157       { 0.50, 0.75 }
 158    };
 159    const GLfloat x = (GLfloat) winx;
 160    const GLfloat y = (GLfloat) winy;
 161    const GLfloat dx0 = v1[0] - v0[0];
 162    const GLfloat dy0 = v1[1] - v0[1];
 163    const GLfloat dx1 = v2[0] - v1[0];
 164    const GLfloat dy1 = v2[1] - v1[1];
 165    const GLfloat dx2 = v0[0] - v2[0];
 166    const GLfloat dy2 = v0[1] - v2[1];
 167    GLint stop = 4, i;
 168    GLfloat insideCount = 16.0F;
 169
 170 #ifdef DEBUG
 171    {
 172       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 173       assert(area >= 0.0);
 174    }
 175 #endif
 176
 177    for (i = 0; i < stop; i++) {
 178       const GLfloat sx = x + samples[i][0];
 179       const GLfloat sy = y + samples[i][1];
 180       const GLfloat fx0 = sx - v0[0];
 181       const GLfloat fy0 = sy - v0[1];
 182       const GLfloat fx1 = sx - v1[0];
 183       const GLfloat fy1 = sy - v1[1];
 184       const GLfloat fx2 = sx - v2[0];
 185       const GLfloat fy2 = sy - v2[1];
 186       /* cross product determines if sample is inside or outside each edge */
 187       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 188       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 189       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 190       /* Check if the sample is exactly on an edge.  If so, let cross be a
 191        * positive or negative value depending on the direction of the edge.
 192        */
 193       if (cross0 == 0.0F)
 194          cross0 = dx0 + dy0;
 195       if (cross1 == 0.0F)
 196          cross1 = dx1 + dy1;
 197       if (cross2 == 0.0F)
 198          cross2 = dx2 + dy2;
 199       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 200          /* point is outside triangle */
 201          insideCount -= 1.0F;
 202          stop = 16;
 203       }
 204    }
 205    if (stop == 4)
 206       return 1.0F;
 207    else
 208       return insideCount * (1.0F / 16.0F);
 209 }
 210
 211
 212
 213 /*
 214  * Compute how much (area) of the given pixel is inside the triangle.
 215  * Vertices MUST be specified in counter-clockwise order.
 216  * Return:  coverage in [0, 15].
 217  */
 218 static GLint
 219 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 220                   const GLfloat v2[3], GLint winx, GLint winy)
 221 {
 222    /* NOTE: 15 samples instead of 16.
 223     * A better sample distribution could be used.
 224     */
 225    static const GLfloat samples[15][2] = {
 226       /* start with the four corners */
 227       { 0.00, 0.00 },
 228       { 0.75, 0.00 },
 229       { 0.00, 0.75 },
 230       { 0.75, 0.75 },
 231       /* continue with interior samples */
 232       { 0.25, 0.00 },
 233       { 0.50, 0.00 },
 234       { 0.00, 0.25 },
 235       { 0.25, 0.25 },
 236       { 0.50, 0.25 },
 237       { 0.75, 0.25 },
 238       { 0.00, 0.50 },
 239       { 0.25, 0.50 },
 240       /*{ 0.50, 0.50 },*/
 241       { 0.75, 0.50 },
 242       { 0.25, 0.75 },
 243       { 0.50, 0.75 }
 244    };
 245    const GLfloat x = (GLfloat) winx;
 246    const GLfloat y = (GLfloat) winy;
 247    const GLfloat dx0 = v1[0] - v0[0];
 248    const GLfloat dy0 = v1[1] - v0[1];
 249    const GLfloat dx1 = v2[0] - v1[0];
 250    const GLfloat dy1 = v2[1] - v1[1];
 251    const GLfloat dx2 = v0[0] - v2[0];
 252    const GLfloat dy2 = v0[1] - v2[1];
 253    GLint stop = 4, i;
 254    GLint insideCount = 15;
 255
 256 #ifdef DEBUG
 257    {
 258       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 259       assert(area >= 0.0);
 260    }
 261 #endif
 262
 263    for (i = 0; i < stop; i++) {
 264       const GLfloat sx = x + samples[i][0];
 265       const GLfloat sy = y + samples[i][1];
 266       const GLfloat fx0 = sx - v0[0];
 267       const GLfloat fy0 = sy - v0[1];
 268       const GLfloat fx1 = sx - v1[0];
 269       const GLfloat fy1 = sy - v1[1];
 270       const GLfloat fx2 = sx - v2[0];
 271       const GLfloat fy2 = sy - v2[1];
 272       /* cross product determines if sample is inside or outside each edge */
 273       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 274       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 275       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 276       /* Check if the sample is exactly on an edge.  If so, let cross be a
 277        * positive or negative value depending on the direction of the edge.
 278        */
 279       if (cross0 == 0.0F)
 280          cross0 = dx0 + dy0;
 281       if (cross1 == 0.0F)
 282          cross1 = dx1 + dy1;
 283       if (cross2 == 0.0F)
 284          cross2 = dx2 + dy2;
 285       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 286          /* point is outside triangle */
 287          insideCount--;
 288          stop = 15;
 289       }
 290    }
 291    if (stop == 4)
 292       return 15;
 293    else
 294       return insideCount;
 295 }
 296
 297
 298
 299 static void
 300 rgba_aa_tri(GLcontext *ctx, GLuint v0, GLuint v1, GLuint v2, GLuint pv)
 301 {
 302 #define DO_Z
 303 #define DO_RGBA
 304 #include "s_aatritemp.h"
 305 }
 306
 307
 308 static void
 309 index_aa_tri(GLcontext *ctx, GLuint v0, GLuint v1, GLuint v2, GLuint pv)
 310 {
 311 #define DO_Z
 312 #define DO_INDEX
 313 #include "s_aatritemp.h"
 314 }
 315
 316
 317 /*
 318  * Compute mipmap level of detail.
 319  */
 320 static INLINE GLfloat
 321 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 322                GLfloat invQ, GLfloat width, GLfloat height)
 323 {
 324    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 325    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 326    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 327    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 328    GLfloat r1 = dudx * dudx + dudy * dudy;
 329    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 330    GLfloat rho2 = r1 + r2;
 331    /* return log base 2 of rho */
 332    return log(rho2) * 1.442695 * 0.5;       /* 1.442695 = 1/log(2) */
 333 }
 334
 335
 336 static void
 337 tex_aa_tri(GLcontext *ctx, GLuint v0, GLuint v1, GLuint v2, GLuint pv)
 338 {
 339 #define DO_Z
 340 #define DO_RGBA
 341 #define DO_TEX
 342 #include "s_aatritemp.h"
 343 }
 344
 345
 346 static void
 347 spec_tex_aa_tri(GLcontext *ctx, GLuint v0, GLuint v1, GLuint v2, GLuint pv)
 348 {
 349 #define DO_Z
 350 #define DO_RGBA
 351 #define DO_TEX
 352 #define DO_SPEC
 353 #include "s_aatritemp.h"
 354 }
 355
 356
 357 static void
 358 multitex_aa_tri(GLcontext *ctx, GLuint v0, GLuint v1, GLuint v2, GLuint pv)
 359 {
 360 #define DO_Z
 361 #define DO_RGBA
 362 #define DO_MULTITEX
 363 #include "s_aatritemp.h"
 364 }
 365
 366 static void
 367 spec_multitex_aa_tri(GLcontext *ctx, GLuint v0, GLuint v1, GLuint v2, GLuint pv)
 368 {
 369 #define DO_Z
 370 #define DO_RGBA
 371 #define DO_MULTITEX
 372 #define DO_SPEC
 373 #include "s_aatritemp.h"
 374 }
 375
 376
 377 /*
 378  * Examine GL state and set ctx->Driver.TriangleFunc to an
 379  * appropriate antialiased triangle rasterizer function.
 380  */
 381 void
 382 _mesa_set_aa_triangle_function(GLcontext *ctx)
 383 {
 384    ASSERT(ctx->Polygon.SmoothFlag);
 385    if (ctx->Texture.ReallyEnabled) {
 386       if (ctx->Light.Enabled &&
 387           ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR) {
 388          if (ctx->Texture.MultiTextureEnabled) {
 389             ctx->Driver.TriangleFunc = spec_multitex_aa_tri;
 390          }
 391          else {
 392             ctx->Driver.TriangleFunc = spec_tex_aa_tri;
 393          }
 394       }
 395       else {
 396          if (ctx->Texture.MultiTextureEnabled) {
 397             ctx->Driver.TriangleFunc = multitex_aa_tri;
 398          }
 399          else {
 400             ctx->Driver.TriangleFunc = tex_aa_tri;
 401          }
 402       }
 403    }
 404    else {
 405       if (ctx->Visual.RGBAflag) {
 406          ctx->Driver.TriangleFunc = rgba_aa_tri;
 407       }
 408       else {
 409          ctx->Driver.TriangleFunc = index_aa_tri;
 410       }
 411    }
 412    ASSERT(ctx->Driver.TriangleFunc);
 413 }