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/macros.h"
34 #include "main/imports.h"
35 #include "main/state.h"
36 #include "s_aatriangle.h"
37 #include "s_context.h"
42 * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
43 * vertices and the given Z values.
44 * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
47 compute_plane(const GLfloat v0
[], const GLfloat v1
[], const GLfloat v2
[],
48 GLfloat z0
, GLfloat z1
, GLfloat z2
, GLfloat plane
[4])
50 const GLfloat px
= v1
[0] - v0
[0];
51 const GLfloat py
= v1
[1] - v0
[1];
52 const GLfloat pz
= z1
- z0
;
54 const GLfloat qx
= v2
[0] - v0
[0];
55 const GLfloat qy
= v2
[1] - v0
[1];
56 const GLfloat qz
= z2
- z0
;
58 /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
59 const GLfloat a
= py
* qz
- pz
* qy
;
60 const GLfloat b
= pz
* qx
- px
* qz
;
61 const GLfloat c
= px
* qy
- py
* qx
;
62 /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
63 on the distance of plane from origin and arbitrary "w" parallel
65 /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
66 which is equal to "-d" below. */
67 const GLfloat d
= -(a
* v0
[0] + b
* v0
[1] + c
* z0
);
77 * Compute coefficients of a plane with a constant Z value.
80 constant_plane(GLfloat value
, GLfloat plane
[4])
88 #define CONSTANT_PLANE(VALUE, PLANE) \
99 * Solve plane equation for Z at (X,Y).
101 static inline GLfloat
102 solve_plane(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
104 assert(plane
[2] != 0.0F
);
105 return (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
109 #define SOLVE_PLANE(X, Y, PLANE) \
110 ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
114 * Solve plane and return clamped GLchan value.
117 solve_plane_chan(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
119 const GLfloat z
= (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
120 #if CHAN_TYPE == GL_FLOAT
121 return CLAMP(z
, 0.0F
, CHAN_MAXF
);
125 else if (z
> CHAN_MAX
)
127 return (GLchan
) IROUND_POS(z
);
132 static inline GLfloat
133 plane_dx(const GLfloat plane
[4])
135 return -plane
[0] / plane
[2];
138 static inline GLfloat
139 plane_dy(const GLfloat plane
[4])
141 return -plane
[1] / plane
[2];
147 * Compute how much (area) of the given pixel is inside the triangle.
148 * Vertices MUST be specified in counter-clockwise order.
149 * Return: coverage in [0, 1].
152 compute_coveragef(const GLfloat v0
[3], const GLfloat v1
[3],
153 const GLfloat v2
[3], GLint winx
, GLint winy
)
155 /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
156 * Contributed by Ray Tice.
158 * Jitter sample positions -
159 * - average should be .5 in x & y for each column
160 * - each of the 16 rows and columns should be used once
161 * - the rectangle formed by the first four points
162 * should contain the other points
163 * - the distrubition should be fairly even in any given direction
165 * The pattern drawn below isn't optimal, but it's better than a regular
166 * grid. In the drawing, the center of each subpixel is surrounded by
167 * four dots. The "x" marks the jittered position relative to the
170 #define POS(a, b) (0.5+a*4+b)/16
171 static const GLfloat samples
[16][2] = {
172 /* start with the four corners */
173 { POS(0, 2), POS(0, 0) },
174 { POS(3, 3), POS(0, 2) },
175 { POS(0, 0), POS(3, 1) },
176 { POS(3, 1), POS(3, 3) },
177 /* continue with interior samples */
178 { POS(1, 1), POS(0, 1) },
179 { POS(2, 0), POS(0, 3) },
180 { POS(0, 3), POS(1, 3) },
181 { POS(1, 2), POS(1, 0) },
182 { POS(2, 3), POS(1, 2) },
183 { POS(3, 2), POS(1, 1) },
184 { POS(0, 1), POS(2, 2) },
185 { POS(1, 0), POS(2, 1) },
186 { POS(2, 1), POS(2, 3) },
187 { POS(3, 0), POS(2, 0) },
188 { POS(1, 3), POS(3, 0) },
189 { POS(2, 2), POS(3, 2) }
192 const GLfloat x
= (GLfloat
) winx
;
193 const GLfloat y
= (GLfloat
) winy
;
194 const GLfloat dx0
= v1
[0] - v0
[0];
195 const GLfloat dy0
= v1
[1] - v0
[1];
196 const GLfloat dx1
= v2
[0] - v1
[0];
197 const GLfloat dy1
= v2
[1] - v1
[1];
198 const GLfloat dx2
= v0
[0] - v2
[0];
199 const GLfloat dy2
= v0
[1] - v2
[1];
201 GLfloat insideCount
= 16.0F
;
203 assert(dx0
* dy1
- dx1
* dy0
>= 0.0); /* area >= 0.0 */
205 for (i
= 0; i
< stop
; i
++) {
206 const GLfloat sx
= x
+ samples
[i
][0];
207 const GLfloat sy
= y
+ samples
[i
][1];
208 /* cross product determines if sample is inside or outside each edge */
209 GLfloat cross
= (dx0
* (sy
- v0
[1]) - dy0
* (sx
- v0
[0]));
210 /* Check if the sample is exactly on an edge. If so, let cross be a
211 * positive or negative value depending on the direction of the edge.
216 /* sample point is outside first edge */
221 /* sample point is inside first edge */
222 cross
= (dx1
* (sy
- v1
[1]) - dy1
* (sx
- v1
[0]));
226 /* sample point is outside second edge */
231 /* sample point is inside first and second edges */
232 cross
= (dx2
* (sy
- v2
[1]) - dy2
* (sx
- v2
[0]));
236 /* sample point is outside third edge */
246 return insideCount
* (1.0F
/ 16.0F
);
252 rgba_aa_tri(struct gl_context
*ctx
,
258 #include "s_aatritemp.h"
263 general_aa_tri(struct gl_context
*ctx
,
270 #include "s_aatritemp.h"
276 * Examine GL state and set swrast->Triangle to an
277 * appropriate antialiased triangle rasterizer function.
280 _swrast_set_aa_triangle_function(struct gl_context
*ctx
)
282 SWcontext
*swrast
= SWRAST_CONTEXT(ctx
);
284 assert(ctx
->Polygon
.SmoothFlag
);
286 if (ctx
->Texture
._EnabledCoordUnits
!= 0
287 || _swrast_use_fragment_program(ctx
)
288 || swrast
->_FogEnabled
289 || _mesa_need_secondary_color(ctx
)) {
290 SWRAST_CONTEXT(ctx
)->Triangle
= general_aa_tri
;
293 SWRAST_CONTEXT(ctx
)->Triangle
= rgba_aa_tri
;
296 assert(SWRAST_CONTEXT(ctx
)->Triangle
);