Change Vector3D definition style

src/engine/geometry.h

@@ -1,10 +1,12 @@
 #ifndef GEOMETRY_H_
 #define GEOMETRY_H_
 
-typedef struct {
+typedef struct Vector3D Vector3D;
+
+struct Vector3D {
 	float x;
 	float y;
 	float z;
-} Vector3D;
+};
 
 #endif