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/macros.h" 35 #include "main/imports.h" 36 #include "main/state.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 ASSERT(dx0 * dy1 - dx1 * dy0 >= 0.0); /* area >= 0.0 */ 219 220 for (i = 0; i < stop; i++) { 221 const GLfloat sx = x + samples[i][0]; 222 const GLfloat sy = y + samples[i][1]; 223 /* cross product determines if sample is inside or outside each edge */ 224 GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0])); 225 /* Check if the sample is exactly on an edge. If so, let cross be a 226 * positive or negative value depending on the direction of the edge. 227 */ 228 if (cross == 0.0F) 229 cross = dx0 + dy0; 230 if (cross < 0.0F) { 231 /* sample point is outside first edge */ 232 insideCount -= 1.0F; 233 stop = 16; 234 } 235 else { 236 /* sample point is inside first edge */ 237 cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0])); 238 if (cross == 0.0F) 239 cross = dx1 + dy1; 240 if (cross < 0.0F) { 241 /* sample point is outside second edge */ 242 insideCount -= 1.0F; 243 stop = 16; 244 } 245 else { 246 /* sample point is inside first and second edges */ 247 cross = (dx2 * (sy - v2[1]) - dy2 * (sx - v2[0])); 248 if (cross == 0.0F) 249 cross = dx2 + dy2; 250 if (cross < 0.0F) { 251 /* sample point is outside third edge */ 252 insideCount -= 1.0F; 253 stop = 16; 254 } 255 } 256 } 257 } 258 if (stop == 4) 259 return 1.0F; 260 else 261 return insideCount * (1.0F / 16.0F); 262 } 263 264 265 266 static void 267 rgba_aa_tri(struct gl_context *ctx, 268 const SWvertex *v0, 269 const SWvertex *v1, 270 const SWvertex *v2) 271 { 272 #define DO_Z 273 #include "s_aatritemp.h" 274 } 275 276 277 static void 278 general_aa_tri(struct gl_context *ctx, 279 const SWvertex *v0, 280 const SWvertex *v1, 281 const SWvertex *v2) 282 { 283 #define DO_Z 284 #define DO_ATTRIBS 285 #include "s_aatritemp.h" 286 } 287 288 289 290 /* 291 * Examine GL state and set swrast->Triangle to an 292 * appropriate antialiased triangle rasterizer function. 293 */ 294 void 295 _swrast_set_aa_triangle_function(struct gl_context *ctx) 296 { 297 SWcontext *swrast = SWRAST_CONTEXT(ctx); 298 299 ASSERT(ctx->Polygon.SmoothFlag); 300 301 if (ctx->Texture._EnabledCoordUnits != 0 302 || _swrast_use_fragment_program(ctx) 303 || swrast->_FogEnabled 304 || _mesa_need_secondary_color(ctx)) { 305 SWRAST_CONTEXT(ctx)->Triangle = general_aa_tri; 306 } 307 else { 308 SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri; 309 } 310 311 ASSERT(SWRAST_CONTEXT(ctx)->Triangle); 312 } 313
