Physics Engine Deep Dive: Part II

Benjamin Jordan
11 min readJul 23, 2024
“Numbers” | Kevin Dooley

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This is part two of a series. Part one can be found here.

In the last article, we defined some terms: we learned what rigid bodies were, breezed through Newtonian kinematics, and developed some simple force models. We also explored the idea of physical stability using Linear Stability Theory (LST). This gave us an explicit method for determining how our force models and parameters affect the stability of the system.

In this article, we are going to deep dive numerical methods. We’re going to try to understand how they work and more importantly, why sometimes they don’t work.

From Wikimedia.

Recap

In Part I, we briefly touched on the fact that numerical methods operate iteratively. That is, given the current state of a system, a numerical method approximates a future state (Why can’t we just figure out the exact solution to a complex system? Among other reasons, see Bonini’s Paradox.). These methods are generally given small time steps like 1/60th or 1/30th of a second where the smaller the time step, the closer the…

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Benjamin Jordan
Benjamin Jordan

Written by Benjamin Jordan

Tech, thought, teaching. Total loser. Founder @SpyreIO, Adjunct @SLU. Formerly VPE @N3TWORK, CTO @Big Run Studios, CTO @Enklu, Studio Tech Director @NCSOFT.