Added bi-linear interpolation for getting Z coordinate at any location in the grid.

main.cpp

@@ -1104,7 +1104,6 @@ private:
 
     using ImageHolder = std::unique_ptr<uint8_t[], void (*)(void *)>;
     std::vector<std::pair<ref<Texture>, ImageHolder>> m_images;
-    int m_current_image;
 };