GLTeapot: normalize quaternion

Quaternions representing rotation should have unit length. Multiplying
quaternions cause error accumulation and length change. Normalizing
quaternion after rotation will avoid that.

Fixes #7160.

Change-Id: I82f1f2b89c326a4d2c956c03296600e79ac267c2
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2270
Reviewed-by: Jérôme Duval <[email protected]>

src/apps/glteapot/GLObject.cpp

@@ -181,6 +181,7 @@ GLObject::RotateWorldSpace(float rx, float ry)
 {
 	fRotation = Quaternion(Vector3(0.0f, 1.0f, 0.0f), 0.01f * rx) * fRotation;
 	fRotation = Quaternion(Vector3(1.0f, 0.0f, 0.0f), 0.01f * ry) * fRotation;
+	fRotation.normalize();
 	changed = true;
 }