GoKawiilPosted on May 10, 2026 by Kyle Croarkin
When was the last time one line of code made you realize how far you’ve come?
For context, I’ve been writing a voxel game in Dyalog APL for nearly 7 months now. I started learning APL 9 months ago to be able to do this. Anything that is able to be done in APL I attempt to do purely in APL in a style befitting for APL. This includes Perlin noise terrain generation, converting internal representations of blocks into geometry to be rendered, frustum culling, collision and a lot more. It is currently able to reach >60 FPS on my MacBook with a render distance of 12, with most of the bottlenecks being silly choices from my part as I learn APL while doing this.
One line of code in this project that I greatly enjoy is the code that checks what faces of a chunk are exposed so that they can be selected and passed to the vertex buffer for the chunk. I like it so much that I even had a section dedicated to it in my talk at DYNA26
↑[0]{edges∨solid>⍵}¨0 1 2∘.{⍵⌽[⍺]solid}¯1 1
Very broad, what it does can be broken up like this.
We have 2 3d boolean arrays solid and edges of size 16 128 16 that represent whether or not a solid block is found in each position. edges only checks if a solid block is found on the edges of the chunk.
0 1 2∘.{⍵⌽[⍺]solid}¯1 1 shifts the solid array in each of the 3 axes 0 1 2 back and forth ¯1 1 . The outer product of it returns a 2d array where each row specifies an axes and the rotation.
solid>⍵}¨ compares each shift with the original array. This being true indicates that the face is visible.
{edges∨ makes it also set all edges to be visible. This is important since shifting wraps around the edges of the array that it shifts towards.
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