2 * Mesa 3-D graphics library
4 * Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
13 * The above copyright notice and this permission notice shall be included
14 * in all copies or substantial portions of the Software.
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
17 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * 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/macros.h"
35 #include "main/imports.h"
36 #include "main/state.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 * Solve plane and return clamped GLchan value.
118 solve_plane_chan(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
120 const GLfloat z
= (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
121 #if CHAN_TYPE == GL_FLOAT
122 return CLAMP(z
, 0.0F
, CHAN_MAXF
);
126 else if (z
> CHAN_MAX
)
128 return (GLchan
) IROUND_POS(z
);
133 static inline GLfloat
134 plane_dx(const GLfloat plane
[4])
136 return -plane
[0] / plane
[2];
139 static inline GLfloat
140 plane_dy(const GLfloat plane
[4])
142 return -plane
[1] / plane
[2];
148 * Compute how much (area) of the given pixel is inside the triangle.
149 * Vertices MUST be specified in counter-clockwise order.
150 * Return: coverage in [0, 1].
153 compute_coveragef(const GLfloat v0
[3], const GLfloat v1
[3],
154 const GLfloat v2
[3], GLint winx
, GLint winy
)
156 /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
157 * Contributed by Ray Tice.
159 * Jitter sample positions -
160 * - average should be .5 in x & y for each column
161 * - each of the 16 rows and columns should be used once
162 * - the rectangle formed by the first four points
163 * should contain the other points
164 * - the distrubition should be fairly even in any given direction
166 * The pattern drawn below isn't optimal, but it's better than a regular
167 * grid. In the drawing, the center of each subpixel is surrounded by
168 * four dots. The "x" marks the jittered position relative to the
171 #define POS(a, b) (0.5+a*4+b)/16
172 static const GLfloat samples
[16][2] = {
173 /* start with the four corners */
174 { POS(0, 2), POS(0, 0) },
175 { POS(3, 3), POS(0, 2) },
176 { POS(0, 0), POS(3, 1) },
177 { POS(3, 1), POS(3, 3) },
178 /* continue with interior samples */
179 { POS(1, 1), POS(0, 1) },
180 { POS(2, 0), POS(0, 3) },
181 { POS(0, 3), POS(1, 3) },
182 { POS(1, 2), POS(1, 0) },
183 { POS(2, 3), POS(1, 2) },
184 { POS(3, 2), POS(1, 1) },
185 { POS(0, 1), POS(2, 2) },
186 { POS(1, 0), POS(2, 1) },
187 { POS(2, 1), POS(2, 3) },
188 { POS(3, 0), POS(2, 0) },
189 { POS(1, 3), POS(3, 0) },
190 { POS(2, 2), POS(3, 2) }
193 const GLfloat x
= (GLfloat
) winx
;
194 const GLfloat y
= (GLfloat
) winy
;
195 const GLfloat dx0
= v1
[0] - v0
[0];
196 const GLfloat dy0
= v1
[1] - v0
[1];
197 const GLfloat dx1
= v2
[0] - v1
[0];
198 const GLfloat dy1
= v2
[1] - v1
[1];
199 const GLfloat dx2
= v0
[0] - v2
[0];
200 const GLfloat dy2
= v0
[1] - v2
[1];
202 GLfloat insideCount
= 16.0F
;
204 assert(dx0
* dy1
- dx1
* dy0
>= 0.0); /* area >= 0.0 */
206 for (i
= 0; i
< stop
; i
++) {
207 const GLfloat sx
= x
+ samples
[i
][0];
208 const GLfloat sy
= y
+ samples
[i
][1];
209 /* cross product determines if sample is inside or outside each edge */
210 GLfloat cross
= (dx0
* (sy
- v0
[1]) - dy0
* (sx
- v0
[0]));
211 /* Check if the sample is exactly on an edge. If so, let cross be a
212 * positive or negative value depending on the direction of the edge.
217 /* sample point is outside first edge */
222 /* sample point is inside first edge */
223 cross
= (dx1
* (sy
- v1
[1]) - dy1
* (sx
- v1
[0]));
227 /* sample point is outside second edge */
232 /* sample point is inside first and second edges */
233 cross
= (dx2
* (sy
- v2
[1]) - dy2
* (sx
- v2
[0]));
237 /* sample point is outside third edge */
247 return insideCount
* (1.0F
/ 16.0F
);
253 rgba_aa_tri(struct gl_context
*ctx
,
259 #include "s_aatritemp.h"
264 general_aa_tri(struct gl_context
*ctx
,
271 #include "s_aatritemp.h"
277 * Examine GL state and set swrast->Triangle to an
278 * appropriate antialiased triangle rasterizer function.
281 _swrast_set_aa_triangle_function(struct gl_context
*ctx
)
283 SWcontext
*swrast
= SWRAST_CONTEXT(ctx
);
285 assert(ctx
->Polygon
.SmoothFlag
);
287 if (ctx
->Texture
._EnabledCoordUnits
!= 0
288 || _swrast_use_fragment_program(ctx
)
289 || swrast
->_FogEnabled
290 || _mesa_need_secondary_color(ctx
)) {
291 SWRAST_CONTEXT(ctx
)->Triangle
= general_aa_tri
;
294 SWRAST_CONTEXT(ctx
)->Triangle
= rgba_aa_tri
;
297 assert(SWRAST_CONTEXT(ctx
)->Triangle
);