(20111215) 12:00

Util.c

@@ -0,0 +1,93 @@
+#include <math.h>
+
+#include "Util.h"
+
+
+/////////////////////////////
+// SolveQuadratic
+//
+// Solves a Quadratic equation using a, b and c coeficients.
+int SolveQuadratic(float a,float b,float c,float *Rmin,float *Rmax){
+	float root;
+	float divisor;
+	float b2;
+	b2=b*b;
+	root=b2-4.0*a*c;
+	if(root<0){
+		// Complex
+		return(0);
+	}
+	divisor=(2.0*a);
+	if(fabs(divisor)==0.0f){
+		// +inf -inf
+		return(0);
+	}
+	root=sqrtf(root);
+	Rmin[0]=(float)((-b-root)/divisor);
+	Rmax[0]=(float)((-b+root)/divisor);
+	return(1);
+}
+
+
+/////////////////////////////
+// Intersec_RayUnitCircle
+//
+// Intersection between a ray and a Unit Circle.
+int Intersec_RayUnitCircle(vec2 orig,vec2 vel,vec2 center,float *t){
+	float a,b,c;
+	float Rmin,Rmax;
+	vec2 temp;
+
+	// Solve as a unit circle
+	a=vec2_dot(vel,vel);
+	if(fabs(a)<0.000001f){
+		return(0);
+	}
+	vec2_minus(temp,orig,center);
+	b=2.0f*vec2_dot(temp,vel);
+	c=vec2_dot(temp,temp)-1.0f;
+	if(SolveQuadratic(a,b,c,&Rmin,&Rmax)){
+		if(Rmin>=-0.0001f && Rmin<Rmax && Rmin<=1.0f){
+			*t=Rmin;
+			return(1);
+		}
+		if(Rmax>=-0.0001f && Rmin>Rmax && Rmax<=1.0f){
+			*t=Rmax;
+			return(1);
+		}
+	}
+	return(0);
+}
+
+
+/////////////////////////////
+// Colision_CircleCircle
+//
+// Colision point of a circle against another circle.
+int Colision_CircleCircle(
+	vec2 cir1[2],float rad1,
+	vec2 cir2,float rad2,
+	float *t,vec2 n)
+{
+	vec2 vel,orig,cen,temp;
+	float rads,invrads;
+
+	// Convert to a unit circle vs ray
+	rads=rad1+rad2;
+	invrads=1.0f/rads;
+	vec2_minus(vel,cir1[1],cir1[0]);
+	vec2_scale(vel,vel,invrads);
+	vec2_scale(orig,cir1[0],invrads);
+	vec2_scale(cen,cir2,invrads);
+	if(Intersec_RayUnitCircle(orig,vel,cen,t)){
+		// Calculate n
+		vec2_minus(vel,cir1[1],cir1[0]);
+		vec2_scale(temp,vel,*t);
+		vec2_plus(temp,cir1[0],temp);
+		vec2_minus(temp,cir2,temp);
+		vec2_scale(n,temp,1.0f/rads);
+		return(1);
+	}
+	return(0);
+}
+