SP4CEBAR 2024-12-07 21:02 (Edited)

Planet terrain!

All it takes is 25 characters, it doesn't need any pixel buffers or raster effects!
This algorithm chooses the right cells to draw a circle.

Two years ago I made my Cell vector intersection analyzer to generate terrain by calculating the intersections between NX's cells and line segments and selecting characters based on that, this worked well for making terrain.
6 months later I tried to use it to make Large circles without fancy graphics. This did draw circles but they were full of jagged edges.
Today I revisited the problem and found that I needed to change the original line-cell intersection finder for a circle-cell intersection finder. Doing so required an understanding of the cell vector intersection analyzer which was full of abbreviated variable names. After renaming those and applying structs I wrote this new algorithm. Who would've guessed this took 9 and a half hours?

This algorithm shares some similarities with a marching squares algorithm

Bug: Inverting X and Y of the circle caused the circle's radius to become zero. Detected by tracing the radius around this subprogram. Fixed
Bug: The other answer of ACOS wasn't accounted for. Detected by staring at the code. Fixed
Bug: Each analysis turned out to span two cells. Detected by turning all cells but the center one off and adding sprites to each. Fixed
Bug: The transition between the upper half and the flipped cell lower half was slightly off. Detected by looking at the output. Adding an experimental offset of four seemed to have helped. Fixed

Cell-Circle Intersection Finder