GoKawiilA DOOM-style raycaster that runs inside a TrueType font's hinting program.
What is this?
TrueType fonts have a built-in virtual machine for grid-fitting glyphs. It's got a stack, storage slots, arithmetic, conditionals, function calls - and it turns out it's Turing-complete. I wanted to see if I could get it to render 3D graphics.
The font file contains a DDA raycasting engine written in TrueType bytecode. The glyph "A" has 16 vertical bar contours, and the hinting program raycasts against a 16x16 tile map and repositions those bars using SCFS instructions to form a 3D perspective view. The whole thing is 6.5 KB.
JS handles movement, enemies, and shooting, then passes coordinates to the font through font-variation-settings . The font does the raycasting and wall rendering. Canvas overlay draws enemies, weapon, and HUD on top.
How it works
I wrote a small compiler that takes a custom DSL and outputs TrueType hinting assembly. The DSL looks like a stripped-down C:
func raycast(col: int) -> int: var ra: int = player_angle + col * 3 - FOV_HALF var dx: int = get_cos(ra) var dy: int = get_sin(ra) ...
This compiles to TT bytecode - FDEF , CALL , RS , WS , SCFS , etc. - and gets injected into a .ttf file along with sin/cos lookup tables and the map data. The compiler handles variable allocation (everything goes into TT storage slots), function definitions (FDEF/ENDF), and a few other things like fixed-point math.
The pipeline: doom.doom -> lexer -> parser -> codegen -> doom.ttf
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