calculate normal matrix once in cpp (performance),

added bool variable to turn light on/off (still needs button),

QtMeshViewer/Source/GeometryEngine.cpp

@@ -191,6 +191,9 @@ void GeometryEngine::drawGeometry(QOpenGLShaderProgram *program, bool wireframe)
 		// Set model matrix
 		program->setUniformValue("m_matrix", it.modelMatrix);
 
+		// Set normal matrix
+		program->setUniformValue("n_matrix", (normMatrix * it.modelMatrix).normalMatrix());
+
 		// decide if this is transparent
 		program->setUniformValue("b_transparent", tmp_transparent);