Uploaded July 2024 | Updated September 2026, 1 week ago

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What happens when two circles collide in a p5.js canvas? In this video, I examine the math and implement idealized elastic collisions in a JavaScript physics simulation. This video supplements the Nature of Code book series in Chapter 6 which uses 3rd party physics libraries to handle collisions rather than a direct implementation. Code: thecodingtrain.com/challenges/184-elastic-collisions

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p5.js Web Editor Sketches:
🕹️ Elastic Collisions: editor.p5js.org/codingtrain/sketches/3DrBb8LCp
🕹️ Elastic Collisions - Quadtree: editor.p5js.org/codingtrain/sketches/z8n19RFz9

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References:
📕 The Nature of Code: natureofcode.com
🛒 Pre-order The Nature of Code: nostarch.com/nature-code
🔗 Elastic Collision: en.wikipedia.org/wiki/Elastic_collision
📃 2-Dimensional Elastic Collisions without Trigonometry: vobarian.com/collisions/2dcollisions2.pdf
📃 Elastic Collisions Formula Derivation: dipamsen.github.io/notebook/page/collisions.pdf

Related Coding Challenges:
🚂 youtu.be/IIrC5Qcb2G4
🚂 youtu.be/OJxEcs0w_kE
🚂 youtu.be/PoW8g67XNxA
🚂 youtu.be/h5ZNcAPXxew

Timestamps:
0:00 Introduction
0:20 The Nature of Code book
1:22 Review background material
4:15 Collision Resolution
5:42 Start Coding
8:48 Add collide() function
10:17 Momentum and kinetic energy
14:15 Line of impact
16:44 Add the formulas
21:25 Simplify the code
22:57 Check for overlap
24:31 Check the particle's kinetic energy
25:48 Fix error
27:30 Add more particles
30:11 Optimizations
30:50 Outro

Editing by Mathieu Blanchette
Animations by Jason Heglund
Music from Epidemic Sound

🚂 Website: thecodingtrain.com
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🔗 p5.js: p5js.org
🔗 p5.js Web Editor: editor.p5js.org
🔗 Processing: processing.org

📄 Code of Conduct: github.com/CodingTrain/Code-of-Conduct

This description was auto-generated. If you see a problem, please open an issue: github.com/CodingTrain/thecodingtrain.com/issues/new

#collisions #physicssimulation #collisiondetection #p5js #javascript