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