2 * Mesa 3-D graphics library
5 * Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
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:
14 * The above copyright notice and this permission notice shall be included
15 * in all copies or substantial portions of the Software.
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.
27 * Antialiased Triangle rasterizers
37 #include "s_aatriangle.h"
38 #include "s_context.h"
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.
48 compute_plane(const GLfloat v0
[], const GLfloat v1
[], const GLfloat v2
[],
49 GLfloat z0
, GLfloat z1
, GLfloat z2
, GLfloat plane
[4])
51 const GLfloat px
= v1
[0] - v0
[0];
52 const GLfloat py
= v1
[1] - v0
[1];
53 const GLfloat pz
= z1
- z0
;
55 const GLfloat qx
= v2
[0] - v0
[0];
56 const GLfloat qy
= v2
[1] - v0
[1];
57 const GLfloat qz
= z2
- z0
;
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
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
);
78 * Compute coefficients of a plane with a constant Z value.
81 constant_plane(GLfloat value
, GLfloat plane
[4])
89 #define CONSTANT_PLANE(VALUE, PLANE) \
100 * Solve plane equation for Z at (X,Y).
102 static INLINE GLfloat
103 solve_plane(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
105 ASSERT(plane
[2] != 0.0F
);
106 return (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
110 #define SOLVE_PLANE(X, Y, PLANE) \
111 ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
115 * Return 1 / solve_plane().
117 static INLINE GLfloat
118 solve_plane_recip(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
120 const GLfloat denom
= plane
[3] + plane
[0] * x
+ plane
[1] * y
;
124 return -plane
[2] / denom
;
129 * Solve plane and return clamped GLchan value.
132 solve_plane_chan(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
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
);
140 else if (z
> CHAN_MAX
)
142 return (GLchan
) IROUND_POS(z
);
149 * Compute how much (area) of the given pixel is inside the triangle.
150 * Vertices MUST be specified in counter-clockwise order.
151 * Return: coverage in [0, 1].
154 compute_coveragef(const GLfloat v0
[3], const GLfloat v1
[3],
155 const GLfloat v2
[3], GLint winx
, GLint winy
)
157 /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
158 * Contributed by Ray Tice.
160 * Jitter sample positions -
161 * - average should be .5 in x & y for each column
162 * - each of the 16 rows and columns should be used once
163 * - the rectangle formed by the first four points
164 * should contain the other points
165 * - the distrubition should be fairly even in any given direction
167 * The pattern drawn below isn't optimal, but it's better than a regular
168 * grid. In the drawing, the center of each subpixel is surrounded by
169 * four dots. The "x" marks the jittered position relative to the
172 #define POS(a, b) (0.5+a*4+b)/16
173 static const GLfloat samples
[16][2] = {
174 /* start with the four corners */
175 { POS(0, 2), POS(0, 0) },
176 { POS(3, 3), POS(0, 2) },
177 { POS(0, 0), POS(3, 1) },
178 { POS(3, 1), POS(3, 3) },
179 /* continue with interior samples */
180 { POS(1, 1), POS(0, 1) },
181 { POS(2, 0), POS(0, 3) },
182 { POS(0, 3), POS(1, 3) },
183 { POS(1, 2), POS(1, 0) },
184 { POS(2, 3), POS(1, 2) },
185 { POS(3, 2), POS(1, 1) },
186 { POS(0, 1), POS(2, 2) },
187 { POS(1, 0), POS(2, 1) },
188 { POS(2, 1), POS(2, 3) },
189 { POS(3, 0), POS(2, 0) },
190 { POS(1, 3), POS(3, 0) },
191 { POS(2, 2), POS(3, 2) }
194 const GLfloat x
= (GLfloat
) winx
;
195 const GLfloat y
= (GLfloat
) winy
;
196 const GLfloat dx0
= v1
[0] - v0
[0];
197 const GLfloat dy0
= v1
[1] - v0
[1];
198 const GLfloat dx1
= v2
[0] - v1
[0];
199 const GLfloat dy1
= v2
[1] - v1
[1];
200 const GLfloat dx2
= v0
[0] - v2
[0];
201 const GLfloat dy2
= v0
[1] - v2
[1];
203 GLfloat insideCount
= 16.0F
;
207 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
212 for (i
= 0; i
< stop
; i
++) {
213 const GLfloat sx
= x
+ samples
[i
][0];
214 const GLfloat sy
= y
+ samples
[i
][1];
215 /* cross product determines if sample is inside or outside each edge */
216 GLfloat cross
= (dx0
* (sy
- v0
[1]) - dy0
* (sx
- v0
[0]));
217 /* Check if the sample is exactly on an edge. If so, let cross be a
218 * positive or negative value depending on the direction of the edge.
223 /* sample point is outside first edge */
228 /* sample point is inside first edge */
229 cross
= (dx1
* (sy
- v1
[1]) - dy1
* (sx
- v1
[0]));
233 /* sample point is outside second edge */
238 /* sample point is inside first and second edges */
239 cross
= (dx2
* (sy
- v2
[1]) - dy2
* (sx
- v2
[0]));
243 /* sample point is outside third edge */
253 return insideCount
* (1.0F
/ 16.0F
);
259 * Compute how much (area) of the given pixel is inside the triangle.
260 * Vertices MUST be specified in counter-clockwise order.
261 * Return: coverage in [0, 15].
264 compute_coveragei(const GLfloat v0
[3], const GLfloat v1
[3],
265 const GLfloat v2
[3], GLint winx
, GLint winy
)
267 /* NOTE: 15 samples instead of 16. */
268 static const GLfloat samples
[15][2] = {
269 /* start with the four corners */
270 { POS(0, 2), POS(0, 0) },
271 { POS(3, 3), POS(0, 2) },
272 { POS(0, 0), POS(3, 1) },
273 { POS(3, 1), POS(3, 3) },
274 /* continue with interior samples */
275 { POS(1, 1), POS(0, 1) },
276 { POS(2, 0), POS(0, 3) },
277 { POS(0, 3), POS(1, 3) },
278 { POS(1, 2), POS(1, 0) },
279 { POS(2, 3), POS(1, 2) },
280 { POS(3, 2), POS(1, 1) },
281 { POS(0, 1), POS(2, 2) },
282 { POS(1, 0), POS(2, 1) },
283 { POS(2, 1), POS(2, 3) },
284 { POS(3, 0), POS(2, 0) },
285 { POS(1, 3), POS(3, 0) }
287 const GLfloat x
= (GLfloat
) winx
;
288 const GLfloat y
= (GLfloat
) winy
;
289 const GLfloat dx0
= v1
[0] - v0
[0];
290 const GLfloat dy0
= v1
[1] - v0
[1];
291 const GLfloat dx1
= v2
[0] - v1
[0];
292 const GLfloat dy1
= v2
[1] - v1
[1];
293 const GLfloat dx2
= v0
[0] - v2
[0];
294 const GLfloat dy2
= v0
[1] - v2
[1];
296 GLint insideCount
= 15;
300 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
305 for (i
= 0; i
< stop
; i
++) {
306 const GLfloat sx
= x
+ samples
[i
][0];
307 const GLfloat sy
= y
+ samples
[i
][1];
308 const GLfloat fx0
= sx
- v0
[0];
309 const GLfloat fy0
= sy
- v0
[1];
310 const GLfloat fx1
= sx
- v1
[0];
311 const GLfloat fy1
= sy
- v1
[1];
312 const GLfloat fx2
= sx
- v2
[0];
313 const GLfloat fy2
= sy
- v2
[1];
314 /* cross product determines if sample is inside or outside each edge */
315 GLfloat cross0
= (dx0
* fy0
- dy0
* fx0
);
316 GLfloat cross1
= (dx1
* fy1
- dy1
* fx1
);
317 GLfloat cross2
= (dx2
* fy2
- dy2
* fx2
);
318 /* Check if the sample is exactly on an edge. If so, let cross be a
319 * positive or negative value depending on the direction of the edge.
327 if (cross0
< 0.0F
|| cross1
< 0.0F
|| cross2
< 0.0F
) {
328 /* point is outside triangle */
342 rgba_aa_tri(GLcontext
*ctx
,
350 #include "s_aatritemp.h"
355 index_aa_tri(GLcontext
*ctx
,
363 #include "s_aatritemp.h"
368 * Compute mipmap level of detail.
369 * XXX we should really include the R coordinate in this computation
370 * in order to do 3-D texture mipmapping.
372 static INLINE GLfloat
373 compute_lambda(const GLfloat sPlane
[4], const GLfloat tPlane
[4],
374 const GLfloat qPlane
[4], GLfloat cx
, GLfloat cy
,
375 GLfloat invQ
, GLfloat texWidth
, GLfloat texHeight
)
377 const GLfloat s
= solve_plane(cx
, cy
, sPlane
);
378 const GLfloat t
= solve_plane(cx
, cy
, tPlane
);
379 const GLfloat invQ_x1
= solve_plane_recip(cx
+1.0F
, cy
, qPlane
);
380 const GLfloat invQ_y1
= solve_plane_recip(cx
, cy
+1.0F
, qPlane
);
381 const GLfloat s_x1
= s
- sPlane
[0] / sPlane
[2];
382 const GLfloat s_y1
= s
- sPlane
[1] / sPlane
[2];
383 const GLfloat t_x1
= t
- tPlane
[0] / tPlane
[2];
384 const GLfloat t_y1
= t
- tPlane
[1] / tPlane
[2];
385 GLfloat dsdx
= s_x1
* invQ_x1
- s
* invQ
;
386 GLfloat dsdy
= s_y1
* invQ_y1
- s
* invQ
;
387 GLfloat dtdx
= t_x1
* invQ_x1
- t
* invQ
;
388 GLfloat dtdy
= t_y1
* invQ_y1
- t
* invQ
;
389 GLfloat maxU
, maxV
, rho
, lambda
;
394 maxU
= MAX2(dsdx
, dsdy
) * texWidth
;
395 maxV
= MAX2(dtdx
, dtdy
) * texHeight
;
396 rho
= MAX2(maxU
, maxV
);
403 tex_aa_tri(GLcontext
*ctx
,
412 #include "s_aatritemp.h"
417 spec_tex_aa_tri(GLcontext
*ctx
,
427 #include "s_aatritemp.h"
433 * Examine GL state and set swrast->Triangle to an
434 * appropriate antialiased triangle rasterizer function.
437 _swrast_set_aa_triangle_function(GLcontext
*ctx
)
439 ASSERT(ctx
->Polygon
.SmoothFlag
);
441 if (ctx
->Texture
._EnabledCoordUnits
!= 0
442 || ctx
->FragmentProgram
._Current
) {
443 if (NEED_SECONDARY_COLOR(ctx
)) {
444 SWRAST_CONTEXT(ctx
)->Triangle
= spec_tex_aa_tri
;
447 SWRAST_CONTEXT(ctx
)->Triangle
= tex_aa_tri
;
450 else if (ctx
->Visual
.rgbMode
) {
451 SWRAST_CONTEXT(ctx
)->Triangle
= rgba_aa_tri
;
454 SWRAST_CONTEXT(ctx
)->Triangle
= index_aa_tri
;
457 ASSERT(SWRAST_CONTEXT(ctx
)->Triangle
);