Added function: Vector3RotateByQuaternion()

Rotate a Vector3 by a Quaternion

src/raymath.h

@@ -122,20 +122,20 @@
         float m2, m6, m10, m14;
         float m3, m7, m11, m15;
     } Matrix;
+
+    // Quaternion type
+    typedef struct Quaternion {
+        float x;
+        float y;
+        float z;
+        float w;
+    } Quaternion;
 #endif
 
 // NOTE: Helper types to be used instead of array return types for *ToFloat functions
 typedef struct float3 { float v[3]; } float3;
 typedef struct float16 { float v[16]; } float16;
 
-// Quaternion type
-typedef struct Quaternion {
-    float x;
-    float y;
-    float z;
-    float w;
-} Quaternion;
-
 #include <math.h>       // Required for: sinf(), cosf(), tan(), fabs()
 
 //----------------------------------------------------------------------------------
@@ -398,6 +398,18 @@ RMDEF Vector3 Vector3Transform(Vector3 v, Matrix mat)
     return result;
 };
 
+// Transform a vector by quaternion rotation
+RMDEF Vector3 Vector3RotateByQuaternion(Vector3 v, Quaternion q)
+{
+    Vector3 result = { 0 };
+
+    result.x = v.x*(q.x*q.x + q.w*q.w - q.y*q.y - q.z*q.z) + v.y*(2*q.x*q.y - 2*q.w*q.z) + v.z*(2*q.x*q.z + 2*q.w*q.y);
+    result.y = v.x*(2*q.w*q.z + 2*q.x*q.y) + v.y*(q.w*q.w - q.x*q.x + q.y*q.y - q.z*q.z) + v.z*(-2*q.w*q.x + 2*q.y*q.z);
+    result.z = v.x*(-2*q.w*q.y + 2*q.x*q.z) + v.y*(2*q.w*q.x + 2*q.y*q.z)+ v.z*(q.w*q.w - q.x*q.x - q.y*q.y + q.z*q.z);
+
+    return result;
+}
+
 // Calculate linear interpolation between two vectors
 RMDEF Vector3 Vector3Lerp(Vector3 v1, Vector3 v2, float amount)
 {