implement motion controllers and vr drawing with brush preview

src/app.h

@@ -52,6 +52,7 @@ public:
     Sampler sampler_stencil;
     Sampler sampler_linear;
     ui::Plane m_face_plane;
+    //ui::Sphere sphere;
     LayoutManager layout;
     NodeMessageBox* msgbox;
     NodeSettings* settings;
@@ -82,6 +83,10 @@ public:
     bool redraw = true;
     bool animate = false;
     bool ui_visible = true;
+    bool vr_active = false;
+    glm::mat4 vr_controller;
+    glm::vec3 vr_controller_pos;
+    float vr_pressure = 1.f;
     glm::mat4 vr_rot{ 0 };
     glm::mat4 vr_uirot{ 0 };
     glm::vec2 cursor{ 0, 0 };