Draw a rope or cable between two posts that sags the right amount for its length

A rope drawn as a simple curve looks right at one length and wrong at others, and a rope that gets longer without hanging lower looks stretched. Here is how to find the real hang from the length of rope and the distance between the posts.

Why this works

A hanging rope takes the one shape where every piece is held up by its neighbours, and that shape is fixed by how much longer the rope is than the gap. Knowing only length and gap, you can find the sag, so a longer rope visibly hangs deeper without any hand-tuning.

When not to use it

Don't use it for a rope that carries weight in the middle, swings, or is pulled sideways: its shape then changes every moment. Move a chain of linked points instead. Also not for posts at different heights without extra work.

In the full entry

• What to build, step by step
• Starting values and the reason for each
• 3 common mistakes and the fix
• 36 lines of example code with 5 checks that pass
• How your AI shows you that it works

Say this to your AI

Use the Spielerando entry "Draw a rope or cable between two posts that sags the right amount for its length" (read_entry rope-bridge-sags-by-its-slack) in my game. Build it step by step, and show me how you checked that it works.

Or skip this and connect the MCP: your AI then finds all of this by itself.Connect the MCP