implement motion controllers and vr drawing with brush preview

src/node_stroke_preview.cpp

@@ -148,7 +148,7 @@ void NodeStrokePreview::handle_resize(glm::vec2 old_size, glm::vec2 new_size)
     m_stroke.reset();
     m_stroke.start(m_brush);
     for (int i = 0; i < 20; i++)
-        m_stroke.add_point(BezierCurve::Bezier2D(kp, i / 20.f), 1.f);
+        m_stroke.add_point(glm::vec3(BezierCurve::Bezier2D(kp, i / 20.f), 0), 1.f);
 
     m_rtt.destroy();
     m_rtt.create((int)new_size.x, (int)new_size.y);