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/macros.h"
35 #include "main/imports.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 * Return 1 / solve_plane().
116 static INLINE GLfloat
117 solve_plane_recip(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
119 const GLfloat denom
= plane
[3] + plane
[0] * x
+ plane
[1] * y
;
123 return -plane
[2] / denom
;
128 * Solve plane and return clamped GLchan value.
131 solve_plane_chan(GLfloat x
, GLfloat y
, const GLfloat plane
[4])
133 const GLfloat z
= (plane
[3] + plane
[0] * x
+ plane
[1] * y
) / -plane
[2];
134 #if CHAN_TYPE == GL_FLOAT
135 return CLAMP(z
, 0.0F
, CHAN_MAXF
);
139 else if (z
> CHAN_MAX
)
141 return (GLchan
) IROUND_POS(z
);
146 static INLINE GLfloat
147 plane_dx(const GLfloat plane
[4])
149 return -plane
[0] / plane
[2];
152 static INLINE GLfloat
153 plane_dy(const GLfloat plane
[4])
155 return -plane
[1] / plane
[2];
161 * Compute how much (area) of the given pixel is inside the triangle.
162 * Vertices MUST be specified in counter-clockwise order.
163 * Return: coverage in [0, 1].
166 compute_coveragef(const GLfloat v0
[3], const GLfloat v1
[3],
167 const GLfloat v2
[3], GLint winx
, GLint winy
)
169 /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
170 * Contributed by Ray Tice.
172 * Jitter sample positions -
173 * - average should be .5 in x & y for each column
174 * - each of the 16 rows and columns should be used once
175 * - the rectangle formed by the first four points
176 * should contain the other points
177 * - the distrubition should be fairly even in any given direction
179 * The pattern drawn below isn't optimal, but it's better than a regular
180 * grid. In the drawing, the center of each subpixel is surrounded by
181 * four dots. The "x" marks the jittered position relative to the
184 #define POS(a, b) (0.5+a*4+b)/16
185 static const GLfloat samples
[16][2] = {
186 /* start with the four corners */
187 { POS(0, 2), POS(0, 0) },
188 { POS(3, 3), POS(0, 2) },
189 { POS(0, 0), POS(3, 1) },
190 { POS(3, 1), POS(3, 3) },
191 /* continue with interior samples */
192 { POS(1, 1), POS(0, 1) },
193 { POS(2, 0), POS(0, 3) },
194 { POS(0, 3), POS(1, 3) },
195 { POS(1, 2), POS(1, 0) },
196 { POS(2, 3), POS(1, 2) },
197 { POS(3, 2), POS(1, 1) },
198 { POS(0, 1), POS(2, 2) },
199 { POS(1, 0), POS(2, 1) },
200 { POS(2, 1), POS(2, 3) },
201 { POS(3, 0), POS(2, 0) },
202 { POS(1, 3), POS(3, 0) },
203 { POS(2, 2), POS(3, 2) }
206 const GLfloat x
= (GLfloat
) winx
;
207 const GLfloat y
= (GLfloat
) winy
;
208 const GLfloat dx0
= v1
[0] - v0
[0];
209 const GLfloat dy0
= v1
[1] - v0
[1];
210 const GLfloat dx1
= v2
[0] - v1
[0];
211 const GLfloat dy1
= v2
[1] - v1
[1];
212 const GLfloat dx2
= v0
[0] - v2
[0];
213 const GLfloat dy2
= v0
[1] - v2
[1];
215 GLfloat insideCount
= 16.0F
;
219 const GLfloat area
= dx0
* dy1
- dx1
* dy0
;
224 for (i
= 0; i
< stop
; i
++) {
225 const GLfloat sx
= x
+ samples
[i
][0];
226 const GLfloat sy
= y
+ samples
[i
][1];
227 /* cross product determines if sample is inside or outside each edge */
228 GLfloat cross
= (dx0
* (sy
- v0
[1]) - dy0
* (sx
- v0
[0]));
229 /* Check if the sample is exactly on an edge. If so, let cross be a
230 * positive or negative value depending on the direction of the edge.
235 /* sample point is outside first edge */
240 /* sample point is inside first edge */
241 cross
= (dx1
* (sy
- v1
[1]) - dy1
* (sx
- v1
[0]));
245 /* sample point is outside second edge */
250 /* sample point is inside first and second edges */
251 cross
= (dx2
* (sy
- v2
[1]) - dy2
* (sx
- v2
[0]));
255 /* sample point is outside third edge */
265 return insideCount
* (1.0F
/ 16.0F
);
271 rgba_aa_tri(GLcontext
*ctx
,
277 #include "s_aatritemp.h"
282 general_aa_tri(GLcontext
*ctx
,
289 #include "s_aatritemp.h"
295 * Examine GL state and set swrast->Triangle to an
296 * appropriate antialiased triangle rasterizer function.
299 _swrast_set_aa_triangle_function(GLcontext
*ctx
)
301 SWcontext
*swrast
= SWRAST_CONTEXT(ctx
);
303 ASSERT(ctx
->Polygon
.SmoothFlag
);
305 if (ctx
->Texture
._EnabledCoordUnits
!= 0
306 || ctx
->FragmentProgram
._Current
307 || swrast
->_FogEnabled
308 || NEED_SECONDARY_COLOR(ctx
)) {
309 SWRAST_CONTEXT(ctx
)->Triangle
= general_aa_tri
;
312 SWRAST_CONTEXT(ctx
)->Triangle
= rgba_aa_tri
;
315 ASSERT(SWRAST_CONTEXT(ctx
)->Triangle
);