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
31 #include "main/glheader.h"
32 #include "main/context.h"
33 #include "main/colormac.h"
34 #include "main/context.h"
35 #include "main/macros.h"
36 #include "main/imports.h"
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
);
147 static INLINE GLfloat
148 plane_dx(const GLfloat plane
[4])
150 return -plane
[0] / plane
[2];
153 static INLINE GLfloat
154 plane_dy(const GLfloat plane
[4])
156 return -plane
[1] / plane
[2];
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].
167 compute_coveragef(const GLfloat v0
[3], const GLfloat v1
[3],
168 const GLfloat v2
[3], GLint winx
, GLint winy
)
170 /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
171 * Contributed by Ray Tice.
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
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
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) }
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];
216 GLfloat insideCount
= 16.0F
;
220 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
225 for (i
= 0; i
< stop
; i
++) {
226 const GLfloat sx
= x
+ samples
[i
][0];
227 const GLfloat sy
= y
+ samples
[i
][1];
228 /* cross product determines if sample is inside or outside each edge */
229 GLfloat cross
= (dx0
* (sy
- v0
[1]) - dy0
* (sx
- v0
[0]));
230 /* Check if the sample is exactly on an edge. If so, let cross be a
231 * positive or negative value depending on the direction of the edge.
236 /* sample point is outside first edge */
241 /* sample point is inside first edge */
242 cross
= (dx1
* (sy
- v1
[1]) - dy1
* (sx
- v1
[0]));
246 /* sample point is outside second edge */
251 /* sample point is inside first and second edges */
252 cross
= (dx2
* (sy
- v2
[1]) - dy2
* (sx
- v2
[0]));
256 /* sample point is outside third edge */
266 return insideCount
* (1.0F
/ 16.0F
);
272 * Compute how much (area) of the given pixel is inside the triangle.
273 * Vertices MUST be specified in counter-clockwise order.
274 * Return: coverage in [0, 15].
277 compute_coveragei(const GLfloat v0
[3], const GLfloat v1
[3],
278 const GLfloat v2
[3], GLint winx
, GLint winy
)
280 /* NOTE: 15 samples instead of 16. */
281 static const GLfloat samples
[15][2] = {
282 /* start with the four corners */
283 { POS(0, 2), POS(0, 0) },
284 { POS(3, 3), POS(0, 2) },
285 { POS(0, 0), POS(3, 1) },
286 { POS(3, 1), POS(3, 3) },
287 /* continue with interior samples */
288 { POS(1, 1), POS(0, 1) },
289 { POS(2, 0), POS(0, 3) },
290 { POS(0, 3), POS(1, 3) },
291 { POS(1, 2), POS(1, 0) },
292 { POS(2, 3), POS(1, 2) },
293 { POS(3, 2), POS(1, 1) },
294 { POS(0, 1), POS(2, 2) },
295 { POS(1, 0), POS(2, 1) },
296 { POS(2, 1), POS(2, 3) },
297 { POS(3, 0), POS(2, 0) },
298 { POS(1, 3), POS(3, 0) }
300 const GLfloat x
= (GLfloat
) winx
;
301 const GLfloat y
= (GLfloat
) winy
;
302 const GLfloat dx0
= v1
[0] - v0
[0];
303 const GLfloat dy0
= v1
[1] - v0
[1];
304 const GLfloat dx1
= v2
[0] - v1
[0];
305 const GLfloat dy1
= v2
[1] - v1
[1];
306 const GLfloat dx2
= v0
[0] - v2
[0];
307 const GLfloat dy2
= v0
[1] - v2
[1];
309 GLint insideCount
= 15;
313 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
318 for (i
= 0; i
< stop
; i
++) {
319 const GLfloat sx
= x
+ samples
[i
][0];
320 const GLfloat sy
= y
+ samples
[i
][1];
321 const GLfloat fx0
= sx
- v0
[0];
322 const GLfloat fy0
= sy
- v0
[1];
323 const GLfloat fx1
= sx
- v1
[0];
324 const GLfloat fy1
= sy
- v1
[1];
325 const GLfloat fx2
= sx
- v2
[0];
326 const GLfloat fy2
= sy
- v2
[1];
327 /* cross product determines if sample is inside or outside each edge */
328 GLfloat cross0
= (dx0
* fy0
- dy0
* fx0
);
329 GLfloat cross1
= (dx1
* fy1
- dy1
* fx1
);
330 GLfloat cross2
= (dx2
* fy2
- dy2
* fx2
);
331 /* Check if the sample is exactly on an edge. If so, let cross be a
332 * positive or negative value depending on the direction of the edge.
340 if (cross0
< 0.0F
|| cross1
< 0.0F
|| cross2
< 0.0F
) {
341 /* point is outside triangle */
354 rgba_aa_tri(GLcontext
*ctx
,
361 #include "s_aatritemp.h"
366 index_aa_tri(GLcontext
*ctx
,
374 #include "s_aatritemp.h"
379 general_aa_tri(GLcontext
*ctx
,
387 #include "s_aatritemp.h"
393 * Examine GL state and set swrast->Triangle to an
394 * appropriate antialiased triangle rasterizer function.
397 _swrast_set_aa_triangle_function(GLcontext
*ctx
)
399 SWcontext
*swrast
= SWRAST_CONTEXT(ctx
);
401 ASSERT(ctx
->Polygon
.SmoothFlag
);
403 if (ctx
->Texture
._EnabledCoordUnits
!= 0
404 || ctx
->FragmentProgram
._Current
405 || swrast
->_FogEnabled
406 || NEED_SECONDARY_COLOR(ctx
)) {
407 SWRAST_CONTEXT(ctx
)->Triangle
= general_aa_tri
;
409 else if (ctx
->Visual
.rgbMode
) {
410 SWRAST_CONTEXT(ctx
)->Triangle
= rgba_aa_tri
;
413 SWRAST_CONTEXT(ctx
)->Triangle
= index_aa_tri
;
416 ASSERT(SWRAST_CONTEXT(ctx
)->Triangle
);