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Fixed intersection test for parallel lines

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This commit is contained in:
Carl Worth 2002-09-17 14:44:52 +00:00
parent a2265c8e1b
commit e9255b4688
2 changed files with 36 additions and 28 deletions
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32
src/xrtraps.c
View file

@ -58,7 +58,7 @@ static double
_ComputeXIntercept (XLineFixed *l, double inverse_slope);
static XFixed
_ComputeIntersect (XLineFixed *l1, XLineFixed *l2);
_LinesIntersect (XLineFixed *l1, XLineFixed *l2, XFixed *intersection);
void
XrTrapsInit(XrTraps *traps)
@ -258,8 +258,8 @@ _ComputeXIntercept (XLineFixed *l, double inverse_slope)
return XFixedToDouble (l->p1.x) - inverse_slope * XFixedToDouble (l->p1.y);
}
static XFixed
_ComputeIntersect (XLineFixed *l1, XLineFixed *l2)
static int
_LinesIntersect (XLineFixed *l1, XLineFixed *l2, XFixed *intersection)
{
/*
* x = m1y + b1
@ -273,7 +273,11 @@ _ComputeIntersect (XLineFixed *l1, XLineFixed *l2)
double m2 = _ComputeInverseSlope (l2);
double b2 = _ComputeXIntercept (l2, m2);
return XDoubleToFixed ((b2 - b1) / (m1 - m2));
if (m1 == m2)
return 0;
*intersection = XDoubleToFixed ((b2 - b1) / (m1 - m2));
return 1;
}
static void
@ -404,16 +408,16 @@ XrTrapsTessellatePolygon (XrTraps *traps,
/* check intersect */
if (en && e->current_x != en->current_x)
{
intersect = _ComputeIntersect (&e->edge, &en->edge);
if (intersect > y) {
/* Need to guarantee that we get all the way past
the intersection point so that the edges sort
properly next time through the loop. */
while (_ComputeX(&e->edge, intersect) < _ComputeX(&en->edge, intersect))
intersect++;
if (intersect < next_y)
next_y = intersect;
}
if (_LinesIntersect (&e->edge, &en->edge, &intersect))
if (intersect > y) {
/* Need to guarantee that we get all the way past
the intersection point so that the edges sort
properly next time through the loop. */
while (_ComputeX(&e->edge, intersect) < _ComputeX(&en->edge, intersect))
intersect++;
if (intersect < next_y)
next_y = intersect;
}
}
}
/* check next inactive point */

32
xrtraps.c
View file

@ -58,7 +58,7 @@ static double
_ComputeXIntercept (XLineFixed *l, double inverse_slope);
static XFixed
_ComputeIntersect (XLineFixed *l1, XLineFixed *l2);
_LinesIntersect (XLineFixed *l1, XLineFixed *l2, XFixed *intersection);
void
XrTrapsInit(XrTraps *traps)
@ -258,8 +258,8 @@ _ComputeXIntercept (XLineFixed *l, double inverse_slope)
return XFixedToDouble (l->p1.x) - inverse_slope * XFixedToDouble (l->p1.y);
}
static XFixed
_ComputeIntersect (XLineFixed *l1, XLineFixed *l2)
static int
_LinesIntersect (XLineFixed *l1, XLineFixed *l2, XFixed *intersection)
{
/*
* x = m1y + b1
@ -273,7 +273,11 @@ _ComputeIntersect (XLineFixed *l1, XLineFixed *l2)
double m2 = _ComputeInverseSlope (l2);
double b2 = _ComputeXIntercept (l2, m2);
return XDoubleToFixed ((b2 - b1) / (m1 - m2));
if (m1 == m2)
return 0;
*intersection = XDoubleToFixed ((b2 - b1) / (m1 - m2));
return 1;
}
static void
@ -404,16 +408,16 @@ XrTrapsTessellatePolygon (XrTraps *traps,
/* check intersect */
if (en && e->current_x != en->current_x)
{
intersect = _ComputeIntersect (&e->edge, &en->edge);
if (intersect > y) {
/* Need to guarantee that we get all the way past
the intersection point so that the edges sort
properly next time through the loop. */
while (_ComputeX(&e->edge, intersect) < _ComputeX(&en->edge, intersect))
intersect++;
if (intersect < next_y)
next_y = intersect;
}
if (_LinesIntersect (&e->edge, &en->edge, &intersect))
if (intersect > y) {
/* Need to guarantee that we get all the way past
the intersection point so that the edges sort
properly next time through the loop. */
while (_ComputeX(&e->edge, intersect) < _ComputeX(&en->edge, intersect))
intersect++;
if (intersect < next_y)
next_y = intersect;
}
}
}
/* check next inactive point */