1 /* $Id: s_aatriangle.c,v 1.28 2003/01/22 15:03:09 brianp Exp $ */
4 * Mesa 3-D graphics library
7 * Copyright (C) 1999-2003 Brian Paul All Rights Reserved.
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the "Software"),
11 * to deal in the Software without restriction, including without limitation
12 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 * and/or sell copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following conditions:
16 * The above copyright notice and this permission notice shall be included
17 * in all copies or substantial portions of the Software.
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
20 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
22 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
23 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
24 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
29 * Antialiased Triangle rasterizers
38 #include "s_aatriangle.h"
39 #include "s_context.h"
44 * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
45 * vertices and the given Z values.
46 * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
49 compute_plane(const GLfloat v0
[], const GLfloat v1
[], const GLfloat v2
[],
50 GLfloat z0
, GLfloat z1
, GLfloat z2
, GLfloat plane
[4])
52 const GLfloat px
= v1
[0] - v0
[0];
53 const GLfloat py
= v1
[1] - v0
[1];
54 const GLfloat pz
= z1
- z0
;
56 const GLfloat qx
= v2
[0] - v0
[0];
57 const GLfloat qy
= v2
[1] - v0
[1];
58 const GLfloat qz
= z2
- z0
;
60 /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
61 const GLfloat a
= py
* qz
- pz
* qy
;
62 const GLfloat b
= pz
* qx
- px
* qz
;
63 const GLfloat c
= px
* qy
- py
* qx
;
64 /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
65 on the distance of plane from origin and arbitrary "w" parallel
67 /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
68 which is equal to "-d" below. */
69 const GLfloat d
= -(a
* v0
[0] + b
* v0
[1] + c
* z0
);
79 * Compute coefficients of a plane with a constant Z value.
82 constant_plane(GLfloat value
, GLfloat plane
[4])
90 #define CONSTANT_PLANE(VALUE, PLANE) \
101 * Solve plane equation for Z at (X,Y).
103 static INLINE GLfloat
104 solve_plane(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
106 ASSERT(plane
[2] != 0.0F
);
107 return (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
111 #define SOLVE_PLANE(X, Y, PLANE) \
112 ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
116 * Return 1 / solve_plane().
118 static INLINE GLfloat
119 solve_plane_recip(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
121 const GLfloat denom
= plane
[3] + plane
[0] * x
+ plane
[1] * y
;
125 return -plane
[2] / denom
;
130 * Solve plane and return clamped GLchan value.
133 solve_plane_chan(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
135 const GLfloat z
= (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
136 #if CHAN_TYPE == GL_FLOAT
137 return CLAMP(z
, 0.0F
, CHAN_MAXF
);
141 else if (z
> CHAN_MAX
)
143 return (GLchan
) IROUND_POS(z
);
150 * Compute how much (area) of the given pixel is inside the triangle.
151 * Vertices MUST be specified in counter-clockwise order.
152 * Return: coverage in [0, 1].
155 compute_coveragef(const GLfloat v0
[3], const GLfloat v1
[3],
156 const GLfloat v2
[3], GLint winx
, GLint winy
)
158 /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
159 * Contributed by Ray Tice.
161 * Jitter sample positions -
162 * - average should be .5 in x & y for each column
163 * - each of the 16 rows and columns should be used once
164 * - the rectangle formed by the first four points
165 * should contain the other points
166 * - the distrubition should be fairly even in any given direction
168 * The pattern drawn below isn't optimal, but it's better than a regular
169 * grid. In the drawing, the center of each subpixel is surrounded by
170 * four dots. The "x" marks the jittered position relative to the
173 #define POS(a, b) (0.5+a*4+b)/16
174 static const GLfloat samples
[16][2] = {
175 /* start with the four corners */
176 { POS(0, 2), POS(0, 0) },
177 { POS(3, 3), POS(0, 2) },
178 { POS(0, 0), POS(3, 1) },
179 { POS(3, 1), POS(3, 3) },
180 /* continue with interior samples */
181 { POS(1, 1), POS(0, 1) },
182 { POS(2, 0), POS(0, 3) },
183 { POS(0, 3), POS(1, 3) },
184 { POS(1, 2), POS(1, 0) },
185 { POS(2, 3), POS(1, 2) },
186 { POS(3, 2), POS(1, 1) },
187 { POS(0, 1), POS(2, 2) },
188 { POS(1, 0), POS(2, 1) },
189 { POS(2, 1), POS(2, 3) },
190 { POS(3, 0), POS(2, 0) },
191 { POS(1, 3), POS(3, 0) },
192 { POS(2, 2), POS(3, 2) }
195 const GLfloat x
= (GLfloat
) winx
;
196 const GLfloat y
= (GLfloat
) winy
;
197 const GLfloat dx0
= v1
[0] - v0
[0];
198 const GLfloat dy0
= v1
[1] - v0
[1];
199 const GLfloat dx1
= v2
[0] - v1
[0];
200 const GLfloat dy1
= v2
[1] - v1
[1];
201 const GLfloat dx2
= v0
[0] - v2
[0];
202 const GLfloat dy2
= v0
[1] - v2
[1];
204 GLfloat insideCount
= 16.0F
;
208 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
213 for (i
= 0; i
< stop
; i
++) {
214 const GLfloat sx
= x
+ samples
[i
][0];
215 const GLfloat sy
= y
+ samples
[i
][1];
216 const GLfloat fx0
= sx
- v0
[0];
217 const GLfloat fy0
= sy
- v0
[1];
218 const GLfloat fx1
= sx
- v1
[0];
219 const GLfloat fy1
= sy
- v1
[1];
220 const GLfloat fx2
= sx
- v2
[0];
221 const GLfloat fy2
= sy
- v2
[1];
222 /* cross product determines if sample is inside or outside each edge */
223 GLfloat cross0
= (dx0
* fy0
- dy0
* fx0
);
224 GLfloat cross1
= (dx1
* fy1
- dy1
* fx1
);
225 GLfloat cross2
= (dx2
* fy2
- dy2
* fx2
);
226 /* Check if the sample is exactly on an edge. If so, let cross be a
227 * positive or negative value depending on the direction of the edge.
235 if (cross0
< 0.0F
|| cross1
< 0.0F
|| cross2
< 0.0F
) {
236 /* point is outside triangle */
244 return insideCount
* (1.0F
/ 16.0F
);
250 * Compute how much (area) of the given pixel is inside the triangle.
251 * Vertices MUST be specified in counter-clockwise order.
252 * Return: coverage in [0, 15].
255 compute_coveragei(const GLfloat v0
[3], const GLfloat v1
[3],
256 const GLfloat v2
[3], GLint winx
, GLint winy
)
258 /* NOTE: 15 samples instead of 16. */
259 static const GLfloat samples
[15][2] = {
260 /* start with the four corners */
261 { POS(0, 2), POS(0, 0) },
262 { POS(3, 3), POS(0, 2) },
263 { POS(0, 0), POS(3, 1) },
264 { POS(3, 1), POS(3, 3) },
265 /* continue with interior samples */
266 { POS(1, 1), POS(0, 1) },
267 { POS(2, 0), POS(0, 3) },
268 { POS(0, 3), POS(1, 3) },
269 { POS(1, 2), POS(1, 0) },
270 { POS(2, 3), POS(1, 2) },
271 { POS(3, 2), POS(1, 1) },
272 { POS(0, 1), POS(2, 2) },
273 { POS(1, 0), POS(2, 1) },
274 { POS(2, 1), POS(2, 3) },
275 { POS(3, 0), POS(2, 0) },
276 { POS(1, 3), POS(3, 0) }
278 const GLfloat x
= (GLfloat
) winx
;
279 const GLfloat y
= (GLfloat
) winy
;
280 const GLfloat dx0
= v1
[0] - v0
[0];
281 const GLfloat dy0
= v1
[1] - v0
[1];
282 const GLfloat dx1
= v2
[0] - v1
[0];
283 const GLfloat dy1
= v2
[1] - v1
[1];
284 const GLfloat dx2
= v0
[0] - v2
[0];
285 const GLfloat dy2
= v0
[1] - v2
[1];
287 GLint insideCount
= 15;
291 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
296 for (i
= 0; i
< stop
; i
++) {
297 const GLfloat sx
= x
+ samples
[i
][0];
298 const GLfloat sy
= y
+ samples
[i
][1];
299 const GLfloat fx0
= sx
- v0
[0];
300 const GLfloat fy0
= sy
- v0
[1];
301 const GLfloat fx1
= sx
- v1
[0];
302 const GLfloat fy1
= sy
- v1
[1];
303 const GLfloat fx2
= sx
- v2
[0];
304 const GLfloat fy2
= sy
- v2
[1];
305 /* cross product determines if sample is inside or outside each edge */
306 GLfloat cross0
= (dx0
* fy0
- dy0
* fx0
);
307 GLfloat cross1
= (dx1
* fy1
- dy1
* fx1
);
308 GLfloat cross2
= (dx2
* fy2
- dy2
* fx2
);
309 /* Check if the sample is exactly on an edge. If so, let cross be a
310 * positive or negative value depending on the direction of the edge.
318 if (cross0
< 0.0F
|| cross1
< 0.0F
|| cross2
< 0.0F
) {
319 /* point is outside triangle */
333 rgba_aa_tri(GLcontext
*ctx
,
341 #include "s_aatritemp.h"
346 index_aa_tri(GLcontext
*ctx
,
354 #include "s_aatritemp.h"
359 * Compute mipmap level of detail.
360 * XXX we should really include the R coordinate in this computation
361 * in order to do 3-D texture mipmapping.
363 static INLINE GLfloat
364 compute_lambda(const GLfloat sPlane
[4], const GLfloat tPlane
[4],
365 const GLfloat qPlane
[4], GLfloat cx
, GLfloat cy
,
366 GLfloat invQ
, GLfloat texWidth
, GLfloat texHeight
)
368 const GLfloat s
= solve_plane(cx
, cy
, sPlane
);
369 const GLfloat t
= solve_plane(cx
, cy
, tPlane
);
370 const GLfloat invQ_x1
= solve_plane_recip(cx
+1.0F
, cy
, qPlane
);
371 const GLfloat invQ_y1
= solve_plane_recip(cx
, cy
+1.0F
, qPlane
);
372 const GLfloat s_x1
= s
- sPlane
[0] / sPlane
[2];
373 const GLfloat s_y1
= s
- sPlane
[1] / sPlane
[2];
374 const GLfloat t_x1
= t
- tPlane
[0] / tPlane
[2];
375 const GLfloat t_y1
= t
- tPlane
[1] / tPlane
[2];
376 GLfloat dsdx
= s_x1
* invQ_x1
- s
* invQ
;
377 GLfloat dsdy
= s_y1
* invQ_y1
- s
* invQ
;
378 GLfloat dtdx
= t_x1
* invQ_x1
- t
* invQ
;
379 GLfloat dtdy
= t_y1
* invQ_y1
- t
* invQ
;
380 GLfloat maxU
, maxV
, rho
, lambda
;
385 maxU
= MAX2(dsdx
, dsdy
) * texWidth
;
386 maxV
= MAX2(dtdx
, dtdy
) * texHeight
;
387 rho
= MAX2(maxU
, maxV
);
394 tex_aa_tri(GLcontext
*ctx
,
403 #include "s_aatritemp.h"
408 spec_tex_aa_tri(GLcontext
*ctx
,
418 #include "s_aatritemp.h"
423 multitex_aa_tri(GLcontext
*ctx
,
432 #include "s_aatritemp.h"
436 spec_multitex_aa_tri(GLcontext
*ctx
,
446 #include "s_aatritemp.h"
451 * Examine GL state and set swrast->Triangle to an
452 * appropriate antialiased triangle rasterizer function.
455 _mesa_set_aa_triangle_function(GLcontext
*ctx
)
457 ASSERT(ctx
->Polygon
.SmoothFlag
);
459 if (ctx
->Texture
._EnabledUnits
!= 0) {
460 if (ctx
->_TriangleCaps
& DD_SEPARATE_SPECULAR
) {
461 if (ctx
->Texture
._EnabledUnits
> 1) {
462 SWRAST_CONTEXT(ctx
)->Triangle
= spec_multitex_aa_tri
;
465 SWRAST_CONTEXT(ctx
)->Triangle
= spec_tex_aa_tri
;
469 if (ctx
->Texture
._EnabledUnits
> 1) {
470 SWRAST_CONTEXT(ctx
)->Triangle
= multitex_aa_tri
;
473 SWRAST_CONTEXT(ctx
)->Triangle
= tex_aa_tri
;
477 else if (ctx
->Visual
.rgbMode
) {
478 SWRAST_CONTEXT(ctx
)->Triangle
= rgba_aa_tri
;
481 SWRAST_CONTEXT(ctx
)->Triangle
= index_aa_tri
;
484 ASSERT(SWRAST_CONTEXT(ctx
)->Triangle
);