+- LDraw.org Discussion Forums (https://forums.ldraw.org)
+-- Forum: General (https://forums.ldraw.org/forum-12.html)
+--- Forum: Official File Specifications/Standards (https://forums.ldraw.org/forum-32.html)
+--- Thread: Cylindrical polygons (/thread-29109.html)
Cylindrical polygons - Peter Blomberg - 2025-10-08
Currently, we have cylindrical polygons with 8, 16, and 48 sides. So, if a part needs a 1-6 sweep, we are forced to use the 48-sided polygon. For very large radii, even 48 sides is not enough. We have 84-sided polygons on the tracker. When we need a cylinder with the number of faces divisible by 5, a custom 50-sided polygon becomes used. What if 16 points are too coarse and 48 points are too dense?
I'd like to solve these by introducing 12, 24, 60, and 84-sided cylinders. The 12-sided is a nice replacement for the 8-sided because three segments make much nicer corners than 2 segments. The 24-sided is perfect when 48 is too much and 16 too little. Both allow 1-6 sweeps. The 60-sided cylinder is more usable than the 50-sided cylinder in that it is divisible by both 3 and 4. The point of the 84-sided cylinder is that the vertexes are distributed differently (divisible by 4, but not by 8) than any multiple of 48, thus allowing vertex optimization at large radii.
The 60-sided cylinder would be used at radii above 36.
The 84-sided cylinder would be used at radii from 80 to 120.
Here's a table showing the segment length for different radii and polygons. Below are recommendations for minima and maxima (radii and segment length) for each polygon optimized for segment length.
The polygon "4" is just a corner made out of one quad at a 45 degree angle.