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Quick return no collision if projectile and player are far apart.

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holycleugh 2018-09-15 11:37:23 -04:00 committed by Andrei Alexeyev
parent 06900313af
commit 0dcdfcb101
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GPG key ID: 363707CD4C7FE8A4
1 changed files with 35 additions and 2 deletions
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37
src/util/geometry.c
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@ -25,11 +25,29 @@ bool point_in_ellipse(complex p, Ellipse e) {
) <= 1;
}
// If segment_ellipse_nonintersection_heuristic returns true, then the
// segment and ellipse do not intersect. However, **the converse is not true**.
// Used for quick returning false in real intersection functions.
static bool segment_ellipse_nonintersection_heuristic(LineSegment seg, Ellipse e) {
Rect seg_bbox = {
.top_left = fmin(creal(seg.a), creal(seg.b)) + I * fmin(cimag(seg.a), cimag(seg.b)),
.bottom_right = fmax(creal(seg.a), creal(seg.b)) + I * fmax(cimag(seg.a), cimag(seg.b))
};
float largest_radius = fmax(creal(e.axes), cimag(e.axes))/2;
Rect e_bbox = {
.top_left = e.origin - largest_radius - I*largest_radius,
.bottom_right = e.origin + largest_radius + I*largest_radius
};
return !rect_rect_intersect(seg_bbox, e_bbox, true);
}
// Is the point of shortest distance between the line through a and b
// and a point c between a and b and closer than r?
// if yes, return f so that a+f*(b-a) is that point.
// otherwise return -1.
double lineseg_circle_intersect(LineSegment seg, Circle c) {
static double lineseg_circle_intersect_fallback(LineSegment seg, Circle c) {
complex m, v;
double projection, lv, lm, distance;
@ -64,10 +82,17 @@ double lineseg_circle_intersect(LineSegment seg, Circle c) {
}
bool lineseg_ellipse_intersect(LineSegment seg, Ellipse e) {
if (segment_ellipse_nonintersection_heuristic(seg, e)) {
return 0;
}
// Transform the coordinate system so that the ellipse becomes a circle
// with origin at (0, 0) and diameter equal to its X axis. Then we can
// calculate the segment-circle intersection.
seg.a -= e.origin;
seg.b -= e.origin;
double ratio = creal(e.axes) / cimag(e.axes);
complex rotation = cexp(I * -e.angle);
seg.a *= rotation;
@ -76,7 +101,15 @@ bool lineseg_ellipse_intersect(LineSegment seg, Ellipse e) {
seg.b = creal(seg.b) + I * ratio * cimag(seg.b);
Circle c = { .radius = creal(e.axes) / 2 };
return lineseg_circle_intersect(seg, c) >= 0;
return lineseg_circle_intersect_fallback(seg, c) >= 0;
}
double lineseg_circle_intersect(LineSegment seg, Circle c) {
Ellipse e = { .origin = c.origin, .axes = 2*c.radius + I*2*c.radius };
if (segment_ellipse_nonintersection_heuristic(seg, e)) {
return 0;
}
return lineseg_circle_intersect_fallback(seg, c) >= 0;
}
bool rect_in_rect(Rect inner, Rect outer) {