Added collision check between ray and box

- Added CheckCollisionRayBox() function.
- Updated and improved core 3d picking example (currently working as
expected).

3 files changed, 32 insertions, 3 deletions

diff --git a/examples/core_3d_picking.c b/examples/core_3d_picking.c
index 2fc05e81..0d6f4ac7 100644
--- a/examples/core_3d_picking.c
+++ b/examples/core_3d_picking.c
@@ -24,9 +24,12 @@ int main()
     Camera camera = {{ 0.0, 10.0, 10.0 }, { 0.0, 0.0, 0.0 }, { 0.0, 1.0, 0.0 }};
 
     Vector3 cubePosition = { 0.0, 1.0, 0.0 };
+    Vector3 cubeSize = { 2.0, 2.0, 2.0 };
     
     Ray ray;        // Picking line ray
     
+    bool collision = false;
+    
     SetCameraMode(CAMERA_FREE);         // Set a free camera mode
     SetCameraPosition(camera.position); // Set internal camera position to match our camera position
 
@@ -45,7 +48,10 @@ int main()
             // NOTE: This function is NOT WORKING properly!
             ray = GetMouseRay(GetMousePosition(), camera);
             
-            // TODO: Check collision between ray and box
+            // Check collision between ray and box
+            collision = CheckCollisionRayBox(ray,
+                (Vector3){cubePosition.x - cubeSize.x / 2,cubePosition.y - cubeSize.y / 2,cubePosition.z - cubeSize.z / 2},
+                (Vector3){cubePosition.x + cubeSize.x / 2,cubePosition.y + cubeSize.y / 2,cubePosition.z + cubeSize.z / 2});
         }
         //----------------------------------------------------------------------------------
 
@@ -57,8 +63,8 @@ int main()
 
             Begin3dMode(camera);
 
-                DrawCube(cubePosition, 2, 2, 2, GRAY);
-                DrawCubeWires(cubePosition, 2, 2, 2, DARKGRAY);
+                DrawCube(cubePosition, cubeSize.x, cubeSize.y, cubeSize.z, GRAY);
+                DrawCubeWires(cubePosition, cubeSize.x, cubeSize.y, cubeSize.z, DARKGRAY);
 
                 DrawGrid(10.0, 1.0);
                 
@@ -67,6 +73,8 @@ int main()
             End3dMode();
             
             DrawText("Try selecting the box with mouse!", 240, 10, 20, GRAY);
+            
+            if(collision) DrawText("BOX SELECTED", (screenWidth - MeasureText("BOX SELECTED", 30)) / 2, screenHeight * 0.1f, 30, GREEN);
 
             DrawFPS(10, 10);
 
diff --git a/src/models.c b/src/models.c
index f78be41d..dd170e0b 100644
--- a/src/models.c
+++ b/src/models.c
@@ -1336,6 +1336,26 @@ bool CheckCollisionBoxSphere(Vector3 minBBox, Vector3 maxBBox, Vector3 centerSph
     return collision;
 }
 
+// Detect collision between ray and box
+bool CheckCollisionRayBox(Ray ray, Vector3 minBBox, Vector3 maxBBox)
+{
+    bool collision = false;
+    
+    float t[8];
+    t[0] = (minBBox.x - ray.position.x) / ray.direction.x;
+    t[1] = (maxBBox.x - ray.position.x) / ray.direction.x;
+    t[2] = (minBBox.y - ray.position.y) / ray.direction.y;
+    t[3] = (maxBBox.y - ray.position.y) / ray.direction.y;
+    t[4] = (minBBox.z - ray.position.z) / ray.direction.z;
+    t[5] = (maxBBox.z - ray.position.z) / ray.direction.z;
+    t[6] = fmax(fmax(fmin(t[0], t[1]), fmin(t[2], t[3])), fmin(t[4], t[5]));
+    t[7] = fmin(fmin(fmax(t[0], t[1]), fmax(t[2], t[3])), fmax(t[4], t[5]));
+    
+    collision = !(t[7] < 0 || t[6] > t[7]);
+    
+    return collision;
+}
+
 // TODO: Useful function to check collision area?
 //BoundingBox GetCollisionArea(BoundingBox box1, BoundingBox box2)
 
diff --git a/src/raylib.h b/src/raylib.h
index 72211b59..b6900a97 100644
--- a/src/raylib.h
+++ b/src/raylib.h
@@ -756,6 +756,7 @@ void DrawBillboardRec(Camera camera, Texture2D texture, Rectangle sourceRec, Vec
 bool CheckCollisionSpheres(Vector3 centerA, float radiusA, Vector3 centerB, float radiusB);                     // Detect collision between two spheres
 bool CheckCollisionBoxes(Vector3 minBBox1, Vector3 maxBBox1, Vector3 minBBox2, Vector3 maxBBox2);               // Detect collision between two boxes
 bool CheckCollisionBoxSphere(Vector3 minBBox, Vector3 maxBBox, Vector3 centerSphere, float radiusSphere);       // Detect collision between box and sphere
+bool CheckCollisionRayBox(Ray ray, Vector3 minBBox, Vector3 maxBBox);                                           // Detect collision between ray and box
 Vector3 ResolveCollisionCubicmap(Image cubicmap, Vector3 mapPosition, Vector3 *playerPosition, float radius);   // Detect collision of player radius with cubicmap
                                                                                                                 // NOTE: Return the normal vector of the impacted surface