Collision Code

From WorkCDN

This is a set of basic collision routines I have written. It's geometry based, not physics. It's currently coded in C++ with fast integer operations. I will at some point in the future try to expand this with some documentation. These collision routines in the public domain. Feel free to use and abuse at will.

#ifndef COLLISION_H_
#define COLLISION_H_
 
namespace collision {
 
	inline bool point_point(const int x1, const int y1, const int x2, const int y2) {
		return x1 == x2 && y1 == y2;
	}
	inline bool point_hline(const int x1, const int y1, const int y2) {
		return y1 == y2;
	}
	inline bool point_vline(const int x1, const int y1, const int x2) {
		return x1 == x2;
	}
	inline bool point_aabox(const int x, const int y, const int l, const int t, const int r, const int b) {
		return x >= l && x <= r && y >= t && y <= b;
	}
	inline bool point_circle(const int x, const int y, const int cx, const int cy, const int r) {
		return ((cx-x)*(cx-x) + (cy-y)*(cy-y)) <= (r*r);
	}
 
	inline bool hline_hline(const int y1, const int y2) {
		return y1 == y2;
	}
	inline bool hline_aabox(const int y, const int l, const int t, const int r, const int b) {
		return y >= t && y <= b;
	}
	inline bool hline_circle(const int y, const int cx, const int cy, const int r) {
		return ((cy>y) ? (cy-y) : (y-cy)) <= r;
	}
 
	inline bool vline_vline(const int x1, const int x2) {
		return x1 == x2;
	}
	inline bool vline_aabox(const int x, const int l, const int t, const int r, const int b) {
		return x >= l && x <= r;
	}
	inline bool vline_circle(const int x, const int cx, const int cy, const int r) {
		return ((cx>x) ? (cx-x) : (x-cx)) <= r;
	}
 
	inline bool aabox_aabox(const int l1, const int t1, const int r1, const int b1, const int l2, const int t2,
													const int r2, const int b2) {
		return (l1 <= r2) && (r1 >= l2) && (t1 <= b2) && (b1 >= t2);
	}
	inline bool aabox_circle(const int l, const int t, const int r, const int b, const int cx, const int cy, const int cr) {
		if (point_aabox(cx, cy, l, t, r, b))
			return true; // if the center point is in the box we definitely collided
		if (cy <= t) {
			if (cx <= l) {
				// check distance to top left point
				return point_circle(l, t, cx, cy, cr);
			}
			if (cx >= r) {
				return point_circle(r, t, cx, cy, cr);
			} else {
				// its above the top segment
				return (t - cy) <= cr;
			}
		}
		if (cy >= b) {
			if (cx >= r) {
				// check distance to bottom right point
				return point_circle(r, b, cx, cy, cr);
			}
			if (cx <= l) {
				// bottom left
				return point_circle(l, b, cx, cy, cr);
			} else {
				// its below the bottom segment
				return (cy - b) <= cr;
			}
		} else {
			// Center is between the top and bottom segments
			// Check the side segments with VLine code
			if (cx <= l) {
				// its to the left
				return (l - cx) <= cr;
			} else {
				// must be to the right
				return (cx - r) <= cr;
			}
		}
	}
 
	inline bool circle_circle(const int cx1, const int cy1, const int r1, const int cx2, const int cy2, const int r2) {
		return ((cx1-cx2)*(cx1-cx2) + (cy1-cy2)*(cy1-cy2)) <= ((r1 + r2) * (r1 + r2));
	}
 
}
 
#endif /*COLLISION_H_*/