public void solve(GameState state) {
// Seed the wiggle value
wiggle = 0x7A7A7A7A ^ state.getFrame();
// Solve each object with respect to another
for (GameThing a : state.getThings()) {
if (a.hasParent()) {
// Things inside buildings vehicles don't have physics
continue;
}
for (GameThing b : state.getThings()) {
if (a == b) {
// Don't push things away from themselves!
continue;
}
if (b.hasParent()) {
// Don't push things that are inside of buildings or vehicles
continue;
}
solveThing(a, b);
}
}
}
protected void solveThing(GameThing a, GameThing b) {
float d; // distance between two objects
float dx; // x distance
float dy; // y distance
float p; // proportion of how much to push away
float c; // constraint distance
if (!a.isMobile() && !b.isMobile()) {
// Both are immobile
return;
}
// calculate distance
dx = b.getX() - a.getX();
dy = b.getY() - a.getY();
if (dx == 0.0f && dy == 0.0f) {
// When the delta vector is zero but we still need to push
// objects around then we create a pseudo-random amount to
// push them so that there is not the same bias every time
dx = dx + ((wiggle % 0xFFFF) / (float) 0xFFFF) * 0.25f;
dy = dy - ((wiggle % 0xFFFF) / (float) 0xFFFF) * 0.25f;
// Recalculate wiggle so that the next two objects
// that wiggle don't push away in the same directions
wiggle = wiggle ^ (a.getID() + b.getID());
}
// calculate the length of the distance vector
d = (float) Math.sqrt(dx * dx + dy * dy);
c = a.getSize() + b.getSize();
if (d >= c) {
// Things don't collide
return;
}
if (!a.isMobile()) {
// Push B away from A
p = -(d - c) / d;
b.translate(dx * p, dy * p);
return;
}
if (!b.isMobile()) {
// Push A away from B
p = (d - c) / d;
a.translate(dx * p, dy * p);
return;
}
// Both are mobile and can be moved
p = (d - c) / d;
a.translate(dx * 0.5f * p, dy * 0.5f * p);
b.translate(dx * -0.5f * p, dy * -0.5f * p);
}
