/**
* Gets the point of collision between a BoundingSphere and a Ray.
*
* @param a
* @param b
* @return
*/
public static Vector3 getCollision(BoundingSphere a, Ray b) {
Vector3 m = b.origin.subtract(a.center);
float e = m.dot(b.direction);
float f = (float) (m.dot(m) - a.radius * a.radius);
// Exit if r’s origin outside s (c > 0) and r pointing away from s (b > 0)
if (f > 0.0f && e > 0.0f) {
return null;
}
float discr = e * e - f;
// A negative discriminant corresponds to ray missing sphere
if (discr < 0.0f) {
return null;
}
// Ray now found to intersect sphere, compute smallest t value of intersection
float t = (float) (-e - MathHelper.sqrt(discr));
// If t is negative, ray started inside sphere so clamp t to zero
if (t < 0.0f) {
t = 0.0f;
}
return b.origin.add(b.direction.multiply(t));
}
/**
* Checks collision between a BoundingSphere and a Ray.
*
* @param a
* @param b
* @return
*/
public static boolean checkCollision(BoundingSphere a, Ray b) {
Vector3 m = b.origin.subtract(a.center);
float e = m.dot(b.direction);
float f = (float) (m.dot(m) - a.radius * a.radius);
// Exit if r’s origin outside s (c > 0) and r pointing away from s (b > 0)
if (f > 0.0f && e > 0.0f) {
return false;
}
float discr = e * e - f;
// A negative discriminant corresponds to ray missing sphere
if (discr < 0.0f) {
return false;
}
// Ray now found to intersect sphere
return true;
}
/**
* Checks the collision between a BoundingSphere and a Segment.
*
* @param a
* @param b
* @return
*/
public static boolean checkCollision(BoundingSphere a, Segment b) {
Vector3 m = b.origin.subtract(a.center);
Vector3 l = b.endpoint.subtract(b.origin);
float lnorm = l.fastLength();
Vector3 d = l.multiply(1f / lnorm);
float e = m.dot(d);
float f = (float) (m.dot(m) - a.radius * a.radius);
// Exit if r’s origin outside s (c > 0) and r pointing away from s (b > 0)
if (f > 0.0f && e > 0.0f) {
return false;
}
float discr = e * e - f;
// A negative discriminant corresponds to ray missing sphere
if (discr < 0.0f) {
return false;
}
// Check that the intersection is not past the segment
return -e - MathHelper.sqrt(discr) <= lnorm;
}
