fixed #588.

cocos2dx/include/CCPointExtension.h

@@ -301,10 +301,22 @@ CCPoint CC_DLL ccpRotateByAngle(const CCPoint& v, const CCPoint& pivot, float an
 	the hit point also is	p1 + s * (p2 - p1);
  @since v0.99.1
  */
-bool CC_DLL ccpLineIntersect(CCPoint p1, CCPoint p2, 
-					  CCPoint p3, CCPoint p4,
+bool CC_DLL ccpLineIntersect(const CCPoint& p1, const CCPoint& p2, 
+					  const CCPoint& p3, const CCPoint& p4,
 					  float *s, float *t);
 
+/*
+ccpSegmentIntersect returns YES if Segment A-B intersects with segment C-D
+@since v1.0.0
+*/
+bool ccpSegmentIntersect(const CCPoint& A, const CCPoint& B, const CCPoint& C, const CCPoint& D);
+
+/*
+ccpIntersectPoint returns the intersection point of line A-B, C-D
+@since v1.0.0
+*/
+CCPoint ccpIntersectPoint(const CCPoint& A, const CCPoint& B, const CCPoint& C, const CCPoint& D);
+
 }//namespace   cocos2d 
 
 #endif // __SUPPORT_CGPOINTEXTENSION_H__

cocos2dx/support/CCPointExtension.cpp

@@ -124,8 +124,36 @@ CCPoint ccpRotateByAngle(const CCPoint& v, const CCPoint& pivot, float angle)
 	return r;
 }
 
-bool ccpLineIntersect(CCPoint A, CCPoint B, 
-					  CCPoint C, CCPoint D,
+
+bool ccpSegmentIntersect(const CCPoint& A, const CCPoint& B, const CCPoint& C, const CCPoint& D)
+{
+    float S, T;
+
+    if( ccpLineIntersect(A, B, C, D, &S, &T )
+        && (S >= 0.0f && S <= 1.0f && T >= 0.0f && T <= 1.0f) )
+        return true;
+
+    return false;
+}
+
+CCPoint ccpIntersectPoint(const CCPoint& A, const CCPoint& B, const CCPoint& C, const CCPoint& D)
+{
+    float S, T;
+
+    if( ccpLineIntersect(A, B, C, D, &S, &T) )
+    {
+        // Point of intersection
+        CCPoint P;
+        P.x = A.x + S * (B.x - A.x);
+        P.y = A.y + S * (B.y - A.y);
+        return P;
+    }
+
+    return CCPointZero;
+}
+
+bool ccpLineIntersect(const CCPoint& A, const CCPoint& B, 
+					  const CCPoint& C, const CCPoint& D,
 					  float *S, float *T)
 {
     // FAIL: Line undefined
@@ -133,51 +161,37 @@ bool ccpLineIntersect(CCPoint A, CCPoint B,
     {
         return false;
     }
+    const float BAx = B.x - A.x;
+    const float BAy = B.y - A.y;
+    const float DCx = D.x - C.x;
+    const float DCy = D.y - C.y;
+    const float ACx = A.x - C.x;
+    const float ACy = A.y - C.y;
 
-    //  Translate system to make A the origin
-    B.x-=A.x; B.y-=A.y;
-    C.x-=A.x; C.y-=A.y;
-    D.x-=A.x; D.y-=A.y;
+    const float denom = DCy*BAx - DCx*BAy;
 
-    // Cache
-    CCPoint C2 = C, D2 = D;
+    *S = DCx*ACy - DCy*ACx;
+    *T = BAx*ACy - BAy*ACx;
 
-    // Length of segment AB
-    float distAB = sqrtf(B.x*B.x+B.y*B.y);
-
-    // Rotate the system so that point B is on the positive X axis.
-    float theCos = B.x/distAB;
-    float theSin = B.y/distAB;
-    float newX = C.x*theCos+C.y*theSin;
-    C.y  = C.y*theCos-C.x*theSin; C.x = newX;
-    newX = D.x*theCos+D.y*theSin;
-    D.y  = D.y*theCos-D.x*theSin; D.x = newX;
-
-    // FAIL: Lines are parallel.
-    if (C.y == D.y)
+    if (denom == 0)
     {
+        if (*S == 0 || *T == 0)
+        { 
+            // Lines incident
+            return true;   
+        }
+        // Lines parallel and not incident
         return false;
     }
 
-    // Discover position of the intersection in the line AB
-    float ABpos = D.x+(C.x-D.x)*D.y/(D.y-C.y);
+    *S = *S / denom;
+    *T = *T / denom;
 
-    // Vector CD
-    C.x = D2.x-C2.x;
-    C.y = D2.y-C2.y;
+    // Point of intersection
+    // CGPoint P;
+    // P.x = A.x + *S * (B.x - A.x);
+    // P.y = A.y + *S * (B.y - A.y);
 
-    // Vector between intersection and point C
-    A.x = ABpos*theCos-C2.x;
-    A.y = ABpos*theSin-C2.y;
-
-    newX = sqrtf((A.x*A.x+A.y*A.y)/(C.x*C.x+C.y*C.y));
-    if(((A.y<0) != (C.y<0)) || ((A.x<0) != (C.x<0)))
-        newX *= -1.0f;
-
-    *S = ABpos/distAB;
-    *T = newX;
-
-    // Success.
     return true;
 }