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
compute_plane(const GLfloat v0[],const GLfloat v1[],const GLfloat v2[],GLfloat z0,GLfloat z1,GLfloat z2,GLfloat plane[4])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
constant_plane(GLfloat value,GLfloat plane[4])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
solve_plane(GLfloat x,GLfloat y,const GLfloat plane[4])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
solve_plane_recip(GLfloat x,GLfloat y,const GLfloat plane[4])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
solve_plane_chan(GLfloat x,GLfloat y,const GLfloat plane[4])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
plane_dx(const GLfloat plane[4])148 plane_dx(const GLfloat plane[4])
149 {
150 return -plane[0] / plane[2];
151 }
152
153 static inline GLfloat
plane_dy(const GLfloat plane[4])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
compute_coveragef(const GLfloat v0[3],const GLfloat v1[3],const GLfloat v2[3],GLint winx,GLint winy)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
rgba_aa_tri(struct gl_context * ctx,const SWvertex * v0,const SWvertex * v1,const SWvertex * v2)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
general_aa_tri(struct gl_context * ctx,const SWvertex * v0,const SWvertex * v1,const SWvertex * v2)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
_swrast_set_aa_triangle_function(struct gl_context * ctx)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