Render heightmap to layer

src/node_panel_grid.h

@@ -28,6 +28,7 @@ public:
     NodeSliderH* m_hm_wireframe;
     NodeSliderH* m_hm_lyaw;
     NodeSliderH* m_hm_lpitch;
+    NodeButton* m_render;
     HeightmapPlane m_hm_plane;
     Image m_hm_image;
     std::string m_file_path;
@@ -37,4 +38,7 @@ public:
     virtual void clone_finalize(Node* dest) const override;
     virtual void init() override;
     void init_controls();
+    float get_height() const;
+    float get_offset() const;
+    void draw_heightmap(const glm::mat4& proj, const glm::mat4& camera) const;
 };