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286 lines
7.9 KiB
C
286 lines
7.9 KiB
C
/*
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* Mesa 3-D graphics library
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* Version: 6.5.3
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*
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* Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* Antialiased Triangle rasterizers
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*/
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#include <precomp.h>
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/*
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* Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
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* vertices and the given Z values.
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* A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
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*/
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static inline void
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compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
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GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
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{
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const GLfloat px = v1[0] - v0[0];
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const GLfloat py = v1[1] - v0[1];
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const GLfloat pz = z1 - z0;
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const GLfloat qx = v2[0] - v0[0];
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const GLfloat qy = v2[1] - v0[1];
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const GLfloat qz = z2 - z0;
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/* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
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const GLfloat a = py * qz - pz * qy;
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const GLfloat b = pz * qx - px * qz;
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const GLfloat c = px * qy - py * qx;
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/* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
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on the distance of plane from origin and arbitrary "w" parallel
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to the plane. */
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/* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
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which is equal to "-d" below. */
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const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
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plane[0] = a;
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plane[1] = b;
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plane[2] = c;
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plane[3] = d;
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}
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/*
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* Compute coefficients of a plane with a constant Z value.
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*/
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static inline void
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constant_plane(GLfloat value, GLfloat plane[4])
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{
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plane[0] = 0.0;
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plane[1] = 0.0;
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plane[2] = -1.0;
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plane[3] = value;
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}
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#define CONSTANT_PLANE(VALUE, PLANE) \
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do { \
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PLANE[0] = 0.0F; \
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PLANE[1] = 0.0F; \
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PLANE[2] = -1.0F; \
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PLANE[3] = VALUE; \
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} while (0)
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/*
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* Solve plane equation for Z at (X,Y).
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*/
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static inline GLfloat
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solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
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{
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ASSERT(plane[2] != 0.0F);
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return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
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}
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#define SOLVE_PLANE(X, Y, PLANE) \
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((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
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/*
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* Solve plane and return clamped GLchan value.
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*/
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static inline GLchan
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solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
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{
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const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
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#if CHAN_TYPE == GL_FLOAT
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return CLAMP(z, 0.0F, CHAN_MAXF);
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#else
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if (z < 0)
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return 0;
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else if (z > CHAN_MAX)
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return CHAN_MAX;
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return (GLchan) IROUND_POS(z);
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#endif
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}
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static inline GLfloat
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plane_dx(const GLfloat plane[4])
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{
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return -plane[0] / plane[2];
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}
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static inline GLfloat
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plane_dy(const GLfloat plane[4])
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{
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return -plane[1] / plane[2];
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}
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/*
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* Compute how much (area) of the given pixel is inside the triangle.
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* Vertices MUST be specified in counter-clockwise order.
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* Return: coverage in [0, 1].
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*/
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static GLfloat
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compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
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const GLfloat v2[3], GLint winx, GLint winy)
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{
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/* Given a position [0,3]x[0,3] return the sub-pixel sample position.
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* Contributed by Ray Tice.
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*
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* Jitter sample positions -
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* - average should be .5 in x & y for each column
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* - each of the 16 rows and columns should be used once
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* - the rectangle formed by the first four points
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* should contain the other points
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* - the distrubition should be fairly even in any given direction
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*
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* The pattern drawn below isn't optimal, but it's better than a regular
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* grid. In the drawing, the center of each subpixel is surrounded by
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* four dots. The "x" marks the jittered position relative to the
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* subpixel center.
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*/
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#define POS(a, b) (0.5+a*4+b)/16
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static const GLfloat samples[16][2] = {
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/* start with the four corners */
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{ POS(0, 2), POS(0, 0) },
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{ POS(3, 3), POS(0, 2) },
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{ POS(0, 0), POS(3, 1) },
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{ POS(3, 1), POS(3, 3) },
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/* continue with interior samples */
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{ POS(1, 1), POS(0, 1) },
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{ POS(2, 0), POS(0, 3) },
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{ POS(0, 3), POS(1, 3) },
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{ POS(1, 2), POS(1, 0) },
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{ POS(2, 3), POS(1, 2) },
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{ POS(3, 2), POS(1, 1) },
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{ POS(0, 1), POS(2, 2) },
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{ POS(1, 0), POS(2, 1) },
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{ POS(2, 1), POS(2, 3) },
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{ POS(3, 0), POS(2, 0) },
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{ POS(1, 3), POS(3, 0) },
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{ POS(2, 2), POS(3, 2) }
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};
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const GLfloat x = (GLfloat) winx;
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const GLfloat y = (GLfloat) winy;
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const GLfloat dx0 = v1[0] - v0[0];
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const GLfloat dy0 = v1[1] - v0[1];
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const GLfloat dx1 = v2[0] - v1[0];
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const GLfloat dy1 = v2[1] - v1[1];
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const GLfloat dx2 = v0[0] - v2[0];
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const GLfloat dy2 = v0[1] - v2[1];
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GLint stop = 4, i;
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GLfloat insideCount = 16.0F;
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ASSERT(dx0 * dy1 - dx1 * dy0 >= 0.0); /* area >= 0.0 */
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for (i = 0; i < stop; i++) {
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const GLfloat sx = x + samples[i][0];
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const GLfloat sy = y + samples[i][1];
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/* cross product determines if sample is inside or outside each edge */
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GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0]));
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/* Check if the sample is exactly on an edge. If so, let cross be a
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* positive or negative value depending on the direction of the edge.
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*/
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if (cross == 0.0F)
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cross = dx0 + dy0;
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if (cross < 0.0F) {
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/* sample point is outside first edge */
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insideCount -= 1.0F;
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stop = 16;
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}
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else {
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/* sample point is inside first edge */
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cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0]));
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if (cross == 0.0F)
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cross = dx1 + dy1;
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if (cross < 0.0F) {
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/* sample point is outside second edge */
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insideCount -= 1.0F;
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stop = 16;
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}
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else {
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/* sample point is inside first and second edges */
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cross = (dx2 * (sy - v2[1]) - dy2 * (sx - v2[0]));
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if (cross == 0.0F)
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cross = dx2 + dy2;
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if (cross < 0.0F) {
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/* sample point is outside third edge */
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insideCount -= 1.0F;
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stop = 16;
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}
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}
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}
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}
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if (stop == 4)
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return 1.0F;
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else
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return insideCount * (1.0F / 16.0F);
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}
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static void
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rgba_aa_tri(struct gl_context *ctx,
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const SWvertex *v0,
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const SWvertex *v1,
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const SWvertex *v2)
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{
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#define DO_Z
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#include "s_aatritemp.h"
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}
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static void
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general_aa_tri(struct gl_context *ctx,
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const SWvertex *v0,
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const SWvertex *v1,
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const SWvertex *v2)
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{
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#define DO_Z
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#define DO_ATTRIBS
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#include "s_aatritemp.h"
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}
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/*
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* Examine GL state and set swrast->Triangle to an
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* appropriate antialiased triangle rasterizer function.
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*/
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void
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_swrast_set_aa_triangle_function(struct gl_context *ctx)
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{
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SWcontext *swrast = SWRAST_CONTEXT(ctx);
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ASSERT(ctx->Polygon.SmoothFlag);
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if (ctx->Texture._EnabledCoord
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|| swrast->_FogEnabled) {
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SWRAST_CONTEXT(ctx)->Triangle = general_aa_tri;
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}
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else {
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SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
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}
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ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
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}
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