// implementation of Seperating Axis Theorem
public boolean intersects(Rectangle b) {
ArrayList<Vector2d> aAxes = getEdgeNormals();
ArrayList<Vector2d> bAxes = b.getEdgeNormals();
for (int i = 0; i < aAxes.size(); i++) {
Vector2d p1 = project(aAxes.get(i));
Vector2d p2 = b.project(aAxes.get(i));
if ((p1.x > p2.y || p2.x > p1.y)) // if they overlap they are intersecting on this axis
return false;
}
for (int i = 0; i < bAxes.size(); i++) {
Vector2d p1 = project(bAxes.get(i));
Vector2d p2 = b.project(bAxes.get(i));
if ((p1.x > p2.y || p2.x > p1.y)) // if they overlap they are intersecting on this axis
return false;
}
return true;
}
public Vector2d intersect(Rectangle b) {
double overlap = Double.MAX_VALUE; // depth
Vector2d collisionNormal = null; // minimum penetration vector or collision normal
ArrayList<Vector2d> aAxes = getEdgeNormals();
ArrayList<Vector2d> bAxes = b.getEdgeNormals();
for (int i = 0; i < aAxes.size(); i++) {
Vector2d p1 = project(aAxes.get(i));
Vector2d p2 = b.project(aAxes.get(i));
if ((p1.x > p2.y || p2.x > p1.y)) // if they overlap they are intersecting on this axis
return null;
else {
double o = Math.min(p1.y, p2.y) - Math.max(p1.x, p2.x);
if (o < overlap) {
overlap = o;
collisionNormal = aAxes.get(i);
}
}
}
for (int i = 0; i < bAxes.size(); i++) {
Vector2d p1 = project(bAxes.get(i));
Vector2d p2 = b.project(bAxes.get(i));
if ((p1.x > p2.y || p2.x > p1.y)) // if they overlap they are intersecting on this axis
return null;
else {
double o = Math.min(p1.y, p2.y) - Math.max(p1.x, p2.x);
if (o < overlap) {
overlap = o;
collisionNormal = bAxes.get(i);
}
}
}
// collision normal and penetration depth has been found
// now we find the most perpendicular edges to the collision normal
Line aEdge = bestEdge(collisionNormal);
Line bEdge = b.bestEdge(new Vector2d(-collisionNormal.x, -collisionNormal.y));
// determine reference and incident edges
Line reference, incident;
Vector2d ref;
boolean flipped = false;
if (aEdge.toVector2d().dot(collisionNormal) <= bEdge.toVector2d().dot(collisionNormal)) {
reference = aEdge;
incident = bEdge;
} else {
reference = bEdge;
incident = aEdge;
flipped = true;
}
ref = reference.toVector2d().normalize();
double offset1 = ref.dot(reference.getPoint1());
ArrayList<Vector2d> clipPoints =
clip(incident.getPoint1(), incident.getPoint2(), new Vector2d(-ref.x, -ref.y), -offset1);
if (clipPoints.size() < 2) return null;
System.out.println("clip1 success");
double offset2 = ref.dot(reference.getPoint2());
clipPoints = clip(clipPoints.get(0), clipPoints.get(1), ref, offset2);
if (clipPoints.size() < 2) return null;
System.out.println("clip2 success");
Vector2d refNormal = ref.getLeftNormal();
if (flipped) refNormal = new Vector2d(refNormal.x * -1, refNormal.y * -1);
double max = refNormal.dot(reference.getPoint1());
if (refNormal.dot(clipPoints.get(0)) - max < 0.0) {
clipPoints.remove(clipPoints.get(0));
if (!clipPoints.isEmpty())
if (refNormal.dot(clipPoints.get(0)) - max < 0.0) clipPoints.remove(clipPoints.get(0));
}
if (!clipPoints.isEmpty()) {
Vector2d collision = new Vector2d(0, 0);
for (int i = 0; i < clipPoints.size(); i++) {
collision =
new Vector2d(collision.x + clipPoints.get(i).x, collision.y + clipPoints.get(i).y);
}
collision = new Vector2d(collision.x / clipPoints.size(), collision.y / clipPoints.size());
return collision;
} else return null;
}
