summaryrefslogtreecommitdiff
path: root/src/mesa/swrast/s_aatriangle.c
blob: 175316790d7bc0cad8ec9e4edf91bcaf9e7e3dbb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
/*
 * Mesa 3-D graphics library
 * Version:  6.5.3
 *
 * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


/*
 * Antialiased Triangle rasterizers
 */


#include "main/glheader.h"
#include "main/context.h"
#include "main/colormac.h"
#include "main/macros.h"
#include "main/imports.h"
#include "s_aatriangle.h"
#include "s_context.h"
#include "s_span.h"


/*
 * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
 * vertices and the given Z values.
 * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
 */
static INLINE void
compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
              GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
{
   const GLfloat px = v1[0] - v0[0];
   const GLfloat py = v1[1] - v0[1];
   const GLfloat pz = z1 - z0;

   const GLfloat qx = v2[0] - v0[0];
   const GLfloat qy = v2[1] - v0[1];
   const GLfloat qz = z2 - z0;

   /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
   const GLfloat a = py * qz - pz * qy;
   const GLfloat b = pz * qx - px * qz;
   const GLfloat c = px * qy - py * qx;
   /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
      on the distance of plane from origin and arbitrary "w" parallel
      to the plane. */
   /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
      which is equal to "-d" below. */
   const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);

   plane[0] = a;
   plane[1] = b;
   plane[2] = c;
   plane[3] = d;
}


/*
 * Compute coefficients of a plane with a constant Z value.
 */
static INLINE void
constant_plane(GLfloat value, GLfloat plane[4])
{
   plane[0] = 0.0;
   plane[1] = 0.0;
   plane[2] = -1.0;
   plane[3] = value;
}

#define CONSTANT_PLANE(VALUE, PLANE)	\
do {					\
   PLANE[0] = 0.0F;			\
   PLANE[1] = 0.0F;			\
   PLANE[2] = -1.0F;			\
   PLANE[3] = VALUE;			\
} while (0)



/*
 * Solve plane equation for Z at (X,Y).
 */
static INLINE GLfloat
solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
{
   ASSERT(plane[2] != 0.0F);
   return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
}


#define SOLVE_PLANE(X, Y, PLANE) \
   ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])


/*
 * Return 1 / solve_plane().
 */
static INLINE GLfloat
solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
{
   const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
   if (denom == 0.0F)
      return 0.0F;
   else
      return -plane[2] / denom;
}


/*
 * Solve plane and return clamped GLchan value.
 */
static INLINE GLchan
solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
{
   const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
#if CHAN_TYPE == GL_FLOAT
   return CLAMP(z, 0.0F, CHAN_MAXF);
#else
   if (z < 0)
      return 0;
   else if (z > CHAN_MAX)
      return CHAN_MAX;
   return (GLchan) IROUND_POS(z);
#endif
}


static INLINE GLfloat
plane_dx(const GLfloat plane[4])
{
   return -plane[0] / plane[2];
}

static INLINE GLfloat
plane_dy(const GLfloat plane[4])
{
   return -plane[1] / plane[2];
}



/*
 * Compute how much (area) of the given pixel is inside the triangle.
 * Vertices MUST be specified in counter-clockwise order.
 * Return:  coverage in [0, 1].
 */
static GLfloat
compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
                  const GLfloat v2[3], GLint winx, GLint winy)
{
   /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
    * Contributed by Ray Tice.
    *
    * Jitter sample positions -
    * - average should be .5 in x & y for each column
    * - each of the 16 rows and columns should be used once
    * - the rectangle formed by the first four points
    *   should contain the other points
    * - the distrubition should be fairly even in any given direction
    *
    * The pattern drawn below isn't optimal, but it's better than a regular
    * grid.  In the drawing, the center of each subpixel is surrounded by
    * four dots.  The "x" marks the jittered position relative to the
    * subpixel center.
    */
#define POS(a, b) (0.5+a*4+b)/16
   static const GLfloat samples[16][2] = {
      /* start with the four corners */
      { POS(0, 2), POS(0, 0) },
      { POS(3, 3), POS(0, 2) },
      { POS(0, 0), POS(3, 1) },
      { POS(3, 1), POS(3, 3) },
      /* continue with interior samples */
      { POS(1, 1), POS(0, 1) },
      { POS(2, 0), POS(0, 3) },
      { POS(0, 3), POS(1, 3) },
      { POS(1, 2), POS(1, 0) },
      { POS(2, 3), POS(1, 2) },
      { POS(3, 2), POS(1, 1) },
      { POS(0, 1), POS(2, 2) },
      { POS(1, 0), POS(2, 1) },
      { POS(2, 1), POS(2, 3) },
      { POS(3, 0), POS(2, 0) },
      { POS(1, 3), POS(3, 0) },
      { POS(2, 2), POS(3, 2) }
   };

   const GLfloat x = (GLfloat) winx;
   const GLfloat y = (GLfloat) winy;
   const GLfloat dx0 = v1[0] - v0[0];
   const GLfloat dy0 = v1[1] - v0[1];
   const GLfloat dx1 = v2[0] - v1[0];
   const GLfloat dy1 = v2[1] - v1[1];
   const GLfloat dx2 = v0[0] - v2[0];
   const GLfloat dy2 = v0[1] - v2[1];
   GLint stop = 4, i;
   GLfloat insideCount = 16.0F;

#ifdef DEBUG
   {
      const GLfloat area = dx0 * dy1 - dx1 * dy0;
      ASSERT(area >= 0.0);
   }
#endif

   for (i = 0; i < stop; i++) {
      const GLfloat sx = x + samples[i][0];
      const GLfloat sy = y + samples[i][1];
      /* cross product determines if sample is inside or outside each edge */
      GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0]));
      /* Check if the sample is exactly on an edge.  If so, let cross be a
       * positive or negative value depending on the direction of the edge.
       */
      if (cross == 0.0F)
         cross = dx0 + dy0;
      if (cross < 0.0F) {
         /* sample point is outside first edge */
         insideCount -= 1.0F;
         stop = 16;
      }
      else {
         /* sample point is inside first edge */
         cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0]));
         if (cross == 0.0F)
            cross = dx1 + dy1;
         if (cross < 0.0F) {
            /* sample point is outside second edge */
            insideCount -= 1.0F;
            stop = 16;
         }
         else {
            /* sample point is inside first and second edges */
            cross = (dx2 * (sy - v2[1]) -  dy2 * (sx - v2[0]));
            if (cross == 0.0F)
               cross = dx2 + dy2;
            if (cross < 0.0F) {
               /* sample point is outside third edge */
               insideCount -= 1.0F;
               stop = 16;
            }
         }
      }
   }
   if (stop == 4)
      return 1.0F;
   else
      return insideCount * (1.0F / 16.0F);
}



static void
rgba_aa_tri(GLcontext *ctx,
	    const SWvertex *v0,
	    const SWvertex *v1,
	    const SWvertex *v2)
{
#define DO_Z
#include "s_aatritemp.h"
}


static void
general_aa_tri(GLcontext *ctx,
               const SWvertex *v0,
               const SWvertex *v1,
               const SWvertex *v2)
{
#define DO_Z
#define DO_ATTRIBS
#include "s_aatritemp.h"
}



/*
 * Examine GL state and set swrast->Triangle to an
 * appropriate antialiased triangle rasterizer function.
 */
void
_swrast_set_aa_triangle_function(GLcontext *ctx)
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);

   ASSERT(ctx->Polygon.SmoothFlag);

   if (ctx->Texture._EnabledCoordUnits != 0
       || ctx->FragmentProgram._Current
       || swrast->_FogEnabled
       || NEED_SECONDARY_COLOR(ctx)) {
      SWRAST_CONTEXT(ctx)->Triangle = general_aa_tri;
   }
   else {
      SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
   }

   ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
}