Why AI-generated fonts don't work in game engines (and the BMFont gap)

Our studio's designer kept running into the same problem: she'd generate a beautiful pixel-art font using an AI image tool, but Godot (and Unity, Phaser, LibGDX) wouldn't accept it. The reason is a format mismatch that trips up a lot of indie developers. What game engines actually need Most game engines use BMFont format for bitmap fonts — a standard originally from AngelCode's Bitmap Font Generator. It consists of two files: font.png — a sprite sheet with all glyphs laid out on a grid font.fnt