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xpbd

by shanecelis

Cart #xpbd-0 | 2023-11-05 | Code ▽ | Embed ▽ | No License

4

Copy and paste the snippet below into your HTML.

<iframe src="https://www.lexaloffle.com/bbs/widget.php?pid=xpbd" allowfullscreen width="621" height="513" style="border:none; overflow:hidden"></iframe>

Library

This is a library to simulate physics using the eXtended Position Based Dynamics (XPBD) methodology.

xpbd.p8

• page 0, library - 1368 tokens
• page 1, demo - 698 tokens

Demo

It contains the following demos you can access with the left and right keys:

• a single bead on a ring;
• multiple beads on a ring;
• a squishy square;
• and an about page with particles.

The bead examples are ports of Matthias Muller's ten minute physics examples.

Usage

Include the first page for the library contents without any demo code.

#include xpbd.p8:0

function _init()
  local a = particle:new { pos = vec(64, 64) } }
  local b = particle:new { pos = vec(74, 64) } }
  sim = xpbd:new { 
    particles = { a, b },
    constraints = { distance_constraint:new { rest_length = 10, a, b } }
  }
end

function _update()
  sim:update()
end

function _draw()
  sim:draw()
end

See demos for how to setup.

Bugs

• I have not optimized the token count yet.
• Collision resolution is not well worked out yet.

Questions

I'm curious if you could use XPBD to make a platformer that felt right. Maybe if it was stiff and used just a one step solver. I have serious doubts but would be fun to see.

License

Copyright (c) 2023 Shane Celis
Released under the MIT license

Acknowlegments

Many thanks to Matthias Muller and his collaborators for XPBD papers, code, examples, and videos that illucidate a refreshingly simple way to simulate physics.

Nice! I always enjoy physics simulations and was entirely unaware of Matthias Muller and his work so thanks for bringing it to my attention.