[shapes] CheckCollisionPointTriangle (fix), CheckCollisionPointLine (new routine) (#1695)

* CheckCollisionPointTriangle

* New feature proposal to existing collision detection routines.
It checks if point [point] belongs to line created between two points [p1] and [p2] with defined margin in pixels[threshold].
1693

1 files changed, 21 insertions, 1 deletions

diff --git a/src/shapes.c b/src/shapes.c
index 89f647d4..789a1f70 100644
--- a/src/shapes.c
+++ b/src/shapes.c
@@ -1468,7 +1468,7 @@ bool CheckCollisionPointTriangle(Vector2 point, Vector2 p1, Vector2 p2, Vector2
 
     float gamma = 1.0f - alpha - beta;
 
-    if ((alpha > 0) && (beta > 0) & (gamma > 0)) collision = true;
+    if ((alpha > 0) && (beta > 0) && (gamma > 0)) collision = true;
 
     return collision;
 }
@@ -1545,6 +1545,26 @@ bool CheckCollisionLines(Vector2 startPos1, Vector2 endPos1, Vector2 startPos2,
     return true;
 }
 
+// Check if point belongs to line created between two points [p1] and [p2] with defined margin in pixels [threshold]
+bool CheckCollisionPointLine(Vector2 point, Vector2 p1, Vector2 p2, int threshold)
+{
+    bool collision = false;
+    float dxc = point.x - p1.x;
+    float dyc = point.y - p1.y;
+    float dxl = p2.x - p1.x;
+    float dyl = p2.y - p1.y;
+    float cross = dxc*dyl - dyc*dxl;
+    
+    if (abs(cross) < threshold*fmaxf(fabsf(dxl), fabsf(dyl)))
+    {
+        if (fabsf(dxl) >= fabsf(dyl)) collision = (dxl > 0)? ((p1.x <= point.x) && (point.x <= p2.x)) : ((p2.x <= point.x) && (point.x <= p1.x));
+        else
+        collision = (dyl > 0)? ((p1.y <= point.y) && (point.y <= p2.y)) : ((p2.y <= point.y) && (point.y <= p1.y));
+    }
+	
+    return collision;
+}
+
 // Get collision rectangle for two rectangles collision
 Rectangle GetCollisionRec(Rectangle rec1, Rectangle rec2)
 {