hmd orient, vr ui

src/canvas.h

@@ -155,7 +155,7 @@ public:
     Sampler m_sampler_mask;
     Sampler m_sampler_stencil;
     Sampler m_sampler_mix;
-    glm::vec2 m_cam_rot{ 0 };
+    glm::mat4 m_cam_rot = glm::mat4(1);
     glm::vec3 m_cam_pos{ 0 };
     float m_cam_fov = 85;
     glm::vec2 m_cur_pos;