Fix heightmap shadow rt and draw the light pos

src/node_panel_grid.h

@@ -32,6 +32,7 @@ public:
     NodeButton* m_render;
     NodeButton* m_commit;
     HeightmapPlane m_hm_plane;
+    Sphere m_sphere;
     Image m_hm_image;
     Texture2D m_texture;
     Sampler m_sampler_linear;