dummy image

In some cases, if textures are missing, dummy images are created.

https://cloud.githubusercontent.com/assets/3192173/16155380/719bd150-34af-11e6-875a-22393d8f7312.jpg default:dirt_with_grass missing: default_grass_side.png available: default_dirt.png, default_dirt_normal.png, default_grass_side_normal.png

https://github.com/minetest/minetest/blob/master/src/client/tile.cpp#L1115-L1147