From 606cc1d897db0a2df201b1c5f7e98bda29d74c64 Mon Sep 17 00:00:00 2001
From: kai-z99 <147789796+kai-z99@users.noreply.github.com>
Date: Wed, 29 May 2024 23:24:44 -0700
Subject: [PATCH] [rshapes]Circle line collision function (#4018)

* inital function

* working 1

* optimize

* optimized dot product

* simplify

* cleanup

* cleanup

* cleanup

* comment

* var name change

* epsilon
---
 src/raylib.h  |  1 +
 src/rshapes.c | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/raylib.h b/src/raylib.h
index 1bf740b9..dfa98efb 100644
--- a/src/raylib.h
+++ b/src/raylib.h
@@ -1295,6 +1295,7 @@ RLAPI bool CheckCollisionPointTriangle(Vector2 point, Vector2 p1, Vector2 p2, Ve
 RLAPI bool CheckCollisionPointPoly(Vector2 point, Vector2 *points, int pointCount);                      // Check if point is within a polygon described by array of vertices
 RLAPI bool CheckCollisionLines(Vector2 startPos1, Vector2 endPos1, Vector2 startPos2, Vector2 endPos2, Vector2 *collisionPoint); // Check the collision between two lines defined by two points each, returns collision point by reference
 RLAPI bool CheckCollisionPointLine(Vector2 point, Vector2 p1, Vector2 p2, int threshold);                // Check if point belongs to line created between two points [p1] and [p2] with defined margin in pixels [threshold]
+RLAPI bool CheckCollisionCircleLine(Vector2 center, float radius, Vector2 p1, Vector2 p2);               // Check if circle collides with a line created betweeen two points [p1] and [p2]
 RLAPI Rectangle GetCollisionRec(Rectangle rec1, Rectangle rec2);                                         // Get collision rectangle for two rectangles collision
 
 //------------------------------------------------------------------------------------
diff --git a/src/rshapes.c b/src/rshapes.c
index 80df64e2..cb85c1c5 100644
--- a/src/rshapes.c
+++ b/src/rshapes.c
@@ -2315,6 +2315,30 @@ bool CheckCollisionPointLine(Vector2 point, Vector2 p1, Vector2 p2, int threshol
     return collision;
 }
 
+// Check if circle collides with a line created betweeen two points [p1] and [p2]
+RLAPI bool CheckCollisionCircleLine(Vector2 center, float radius, Vector2 p1, Vector2 p2)
+{
+    float dx = p1.x - p2.x;
+    float dy = p1.y - p2.y;
+
+    if ((fabsf(dx) + fabsf(dy)) <= FLT_EPSILON)
+    {
+        return CheckCollisionCircles(p1, 0, center, radius);
+    }
+
+    float lengthSQ = ((dx * dx) + (dy * dy));
+    float dotProduct = (((center.x - p1.x) * (p2.x - p1.x)) + ((center.y - p1.y) * (p2.y - p1.y))) / (lengthSQ);
+
+    if (dotProduct > 1.0f) dotProduct = 1.0f;
+    else if (dotProduct < 0.0f) dotProduct = 0.0f;
+
+    float dx2 = (p1.x - (dotProduct * (dx))) - center.x;
+    float dy2 = (p1.y - (dotProduct * (dy))) - center.y;
+    float distanceSQ = ((dx2 * dx2) + (dy2 * dy2));
+
+    return (distanceSQ <= radius * radius);
+}
+
 // Get collision rectangle for two rectangles collision
 Rectangle GetCollisionRec(Rectangle rec1, Rectangle rec2)
 {