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erin_catto

@erin_catto@mastodon.gamedev.place

Game Physics/Animation

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erin_catto, to random
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Can I get a lift?

video/mp4

erin_catto,
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@nolokor it is the solver I call "TGS_Soft" that I developed in Solver2D then ported to Box2D. This sample is running in Box2D.

erin_catto, to random
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Rounded polygon testing with a new SDF polygon renderer.

video/mp4

erin_catto,
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@synlogic this is Box2D version 3 (alpha).

erin_catto,
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@slembcke Correct! Basically this: https://www.shadertoy.com/view/lfdSRf

erin_catto, to random
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Testing stuff today and this happened.

video/mp4

erin_catto,
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@slembcke @demofox Yeah, the oscillating shape is waking up the island on the left. This is the correct and desired behavior.

This oscillation and the island waking and sleeping over and over is a very rare configuration. This configuration was the result of spawning several random shapes.

No problems here, just physics being physics.

erin_catto, (edited ) to random
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Box2D needs a lot of rigid bodies to properly test scaling. This test has 49.5k bodies. I'm pleased with the scaling to 8 cores (factor of 6x). At 9+ cores the separate CCX (chiplets) on this CPU become a problem.

erin_catto, to random
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Working to fix this now. Optimizing cache usage. Hopefully that fixes it.

erin_catto,
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@seanmiddleditch
yes, but it shouldn't be this bad based on what I've seen others achieve on chiplet based CPUs

erin_catto, to random
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Is there anything similar to AMD uProf or Intel VTune for Apple Silicon? I want low level details like cache misses.

erin_catto, to random
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Has any game ever shipped with substantial rigid body simulation running on the GPU? Not soft body stuff. I mean things like vehicles, ragdolls, and destruction.

erin_catto,
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@idbrii I believe PhysX runs on the GPU or at least it used to. I'm not sure what games shipped for the Ageia PPU. I only recall it being used for non-gameplay physics (particles).

erin_catto, to random
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Life is a house of cards. Let's try to stabilize it. https://www.youtube.com/watch?v=6dpVxgR7xoc

erin_catto, to random
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Is there anything to keep GDC presenters from doing their presentations again outside of the GDC and uploading the video somewhere? The paywall, low quality recordings, and low quality web interface are a problem.

erin_catto,
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@gorlak Good to know. I wish the GDC was more open with its recordings.
CppCon is a good example. They release most of their videos after a few months. Some of the recordings are 4k.

andykorth, to random
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First experiment with Hugo wasn't too good. First template I picked doesn't work, eventually found a github issues page with half a dozen people also unable to use it. Second hugo theme was missing an installation step (found the fix on an old closed github issue). Then it required go and npm, where it installed 480 packages (!) warned me that the module wasn't compatible with the latest Hugo version, then after 7000 ms of build time, it failed to render the "taxonomy".

erin_catto,
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@slembcke @andykorth finding a good theme is the hardest part of setting up Hugo. Took me a while to find the one I'm using for box2d.org. I love the Hugo workflow otherwise. And they just added better math support.

erin_catto, to random
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Recently I started a side project called Solver2D https://github.com/erincatto/solver2d. The idea is to create a platform for prototyping and comparing many different 2D rigid body solvers. So far there are 8 solvers including PGS, TGS, NGS, and XPBD. I've created many tests that push these solvers to their limits. Read about it here https://box2d.org/posts/2024/02/solver2d/ and see the solvers compared here https://www.youtube.com/watch?v=sKHf_o_UCzI

erin_catto,
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@johanhelsing someone else also mentioned this as well, so I added a simple performance analysis to my post and a short video showing balanced iterations

erin_catto,
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@slembcke soft constraints can act as a low-pass filter for sub-stepping noise/energy. Direct solvers use regularization, which is similar to constraint softness, to deal with over-constrained problems. So they seem like a generally good thing.

On XPBD, the paper I'm following keeps the velocity and position separate. When there is collision overlap, delta positions can imply huge velocities that are not meaningful.

erin_catto, to random
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It's happening!

erin_catto, to random
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Current Box2D v3 build time measured using: https://github.com/Viladoman/CompileScore

erin_catto, to random
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Ported Box2D v3 to Linux running with 4 cores on a Raspberry Pi 5.

erin_catto, to random
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"Sphyl" in Unreal is a great example of "not invented here". I'm glad it is there to remind us to look outside our own capsules.

erin_catto, to random
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Anyone know a good workflow to automate benchmarks? I would like to periodically run benchmarks on the box2d GitHub repo and catch regressions as well as track performance history graphically.

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