/*
* 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/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])
{
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])
/*
* 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
); }