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collide: handle degenerate case for into-sphere test more robustly

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This case happens, for example, when colliding a capsule with identical begin and end points into a sphere.
This commit is contained in:
rdb 2019-03-29 13:28:53 +01:00
parent 63a764a61b
commit 3ea562d404
1 changed files with 9 additions and 3 deletions
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12
panda/src/collide/collisionSphere.cxx
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@ -620,14 +620,20 @@ intersects_line(double &t1, double &t2,
double A = dot(delta, delta); double A = dot(delta, delta);
nassertr(A != 0.0, false);
LVector3 fc = from - get_center(); LVector3 fc = from - get_center();
double B = 2.0f* dot(delta, fc);
double fc_d2 = dot(fc, fc); double fc_d2 = dot(fc, fc);
double radius = get_radius() + inflate_radius; double radius = get_radius() + inflate_radius;
double C = fc_d2 - radius * radius; double C = fc_d2 - radius * radius;
if (A == 0.0) {
// Degenerate case where delta is zero. This is effectively a test
// against a point (or sphere, for nonzero inflate_radius).
t1 = 0.0;
t2 = 0.0;
return C < 0.0;
}
double B = 2.0f * dot(delta, fc);
double radical = B*B - 4.0*A*C; double radical = B*B - 4.0*A*C;
if (IS_NEARLY_ZERO(radical)) { if (IS_NEARLY_ZERO(radical)) {