/* 
   Fast Circle-Rectangle Intersection Checking
   by Clifford A. Shaffer
   from "Graphics Gems", Academic Press, 1990
   */

#include "GraphicsGems.h"

boolean Check_Intersect(Box2 *R, Point2 *C, double Rad)

	/* Return TRUE iff rectangle R intersects circle with centerpoint C and
	   radius Rad. */
{
	double Rad2;

	Rad2 = Rad * Rad;
	/* Translate coordinates, placing C at the origin. */
	R->max.x -= C->x;  R->max.y -= C->y;
	R->min.x -= C->x;  R->min.y -= C->y;

	if (R->max.x < 0) 			/* R to left of circle center */
		if (R->max.y < 0) 		/* R in lower left corner */
			return ((R->max.x * R->max.x + R->max.y * R->max.y) < Rad2);
		else if (R->min.y > 0) 	/* R in upper left corner */
			return ((R->max.x * R->max.x + R->min.y * R->min.y) < Rad2);
		else 					/* R due West of circle */
			return(ABS(R->max.x) < Rad);
	else if (R->min.x > 0)  	/* R to right of circle center */
		if (R->max.y < 0) 	/* R in lower right corner */
			return ((R->min.x * R->min.x + R->max.y * R->max.y) < Rad2);
		else if (R->min.y > 0)  	/* R in upper right corner */
			return ((R->min.x * R->min.x + R->min.y * R->min.y) < Rad2);
		else 				/* R due East of circle */
			return (R->min.x < Rad);
	else				/* R on circle vertical centerline */
		if (R->max.y < 0) 	/* R due South of circle */
			return (ABS(R->max.y) < Rad);
		else if (R->min.y > 0)  	/* R due North of circle */
			return (R->min.y < Rad);
		else 				/* R contains circle centerpoint */
			return(TRUE);
}