Texture atlas creation

[mosra]

• Probably something similar to what freetype-gl uses?
• https://github.com/juj/RectangleBinPack
• something from nvidia-texture-tools?
• https://observablehq.com/@mourner/simple-rectangle-packing
• https://github.com/TeamHypersomnia/rectpack2D

Barebone joke implementation is now in https://github.com/mosra/magnum/blob/master/src/TextureTools/Atlas.cpp. Also -- would it be possible to preestimate atlas size to avoid specifying it manually?

[ArEnSc]

I think I would be genuinely interested in doing this based on the RectangleBinPack Algorithm which is something I wanted to implement a while ago. This will be looked at after the windowless opengl fix.

[mosra]

Would be great to finish this before the issue turns 10 years old, heh.

Just for the record, an alternative and very specialized algorithm was added recently: https://blog.magnum.graphics/backstage/pot-array-packing/

[ArEnSc]

LMFAO!!!!! omg. Better late than never! =) have fun

[mosra]

Okay, it had to take 11 years after all. As of 66bf0b2 there's a new TextureTools::AtlasLandfill packer, which is based on a very simple idea of tracking currently filled height and filling the image in a linear fashion bottom-up. Thus, "Landfill". It's also capable of incremental packing and has support for texture arrays.

Combined with pre-sorting the items from highest to shortest and making the items all the same orientation it has efficiency comparable to stb_rect_pack, while being significantly faster. This is just an initial implementation aimed at glyph packing however, its efficiency and speed properties, especially for packing larger and more varying input sizes, are likely to improve further.