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Open-sourcing the MuJoCo physics simulator for robotics

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Re: Open-sourcing the MuJoCo physics simulator for robotics

#71

Post by lostdog »

tiborsaas wrote: post #24
6gvONxR4sf7o wrote: post #18

Earlier quoted context omitted.

I have personally spent tons of time dealing with models exploiting physics issues. It’s a major issue. It’s true that either can adequately simulate the setups, but is it true that either can be equally exploited? I genuinely don’t know. I kinda assumed physx is more exploitable.

What kind of exploits are you talking about? Cheating in games for example?

Say you're teaching a robot to walk, but the joint constraints in the simulator aren't quite right. It would be possible for the policy to exert more torque on the joint than it's supposed to be able to in real life. Take that policy and put it on a real robot and it won't work.

Re: Open-sourcing the MuJoCo physics simulator for robotics

#72

Post by Animats »

The demo object that turns itself over is nice.

I used to use a rattleback as a test back when I was working on accurate but slow physics engines in the 1990s. That's an ellipsoid cut by a plane that isn't axis-aligned. You spin it, and it spins, stops, rocks, and spins a bit in the other direction. Very similar to what they're doing.

The key to this is a multi-point contact model. If your contacts are single points, the frictional effects are wrong. It's not that hard to do this. I held a patent on that (#6,067,096), and there was a product called Falling Bodies, the first ragdoll system that really worked.

It was just too early in the 1990s. 100 MIPS was not enough.

Re: Open-sourcing the MuJoCo physics simulator for robotics

#73

Post by regularfry »

CamperBob2 wrote: post #66
regularfry wrote: post #19

Earlier quoted context omitted.

Wonderful that you had thousands of dollars as an undergrad to be able to do so.

I'm not even sure what virtue you're trying to signal here. Just because someone used the limited funds they had available to obtain the software and educational resources they were interested in, they've exercised some sort of inappropriate privilege? Isn't that the whole idea behind college? Spend money to learn cool stuff?

Ok, I'll spell it out. Presenting the idea that MuJoCo having a license fee rather than being free is better, not worse, or even that the difference doesn't matter because "well, I paid for stuff" is the inappropriate part of the privilege. Given a choice between "I can learn X but I need to spend significant money on it" and "I can learn X for free", with everything else equal arguing for the former is exclusionary.

Re: Open-sourcing the MuJoCo physics simulator for robotics

#74

Post by pol4ko »

TaylorAlexander wrote: post #46
rg111 wrote: post #30

MuJoCo is the standard in much of robotics, and recently in the Deep RL space. When I was learning Deep RL, I edged on what could be done through OpenAI gym, or self-made environments, I decided to begin working with MuJoCo. But for an undergrad student from a developing country, the fees were extremely high. So, I just didn't go forward with Deep RL much. I dabbled for a while and tried using PyBullet. Did not go th…

I similarly did not get in to using MuJoCo because I want all my work to be reproducible with open source. So I spent time trying to get RL working in Godot video game engine, but ran in to some road blocks. I know MuJoCo already has all the necessary pipelines so this is exciting indeed!

Hi. Do you mind sharing more of your work with Godot? I'm working in a similar project for software testing.

Re: Open-sourcing the MuJoCo physics simulator for robotics

#75

Post by CamperBob2 »

regularfry wrote: post #73
CamperBob2 wrote: post #66

Earlier quoted context omitted.

I'm not even sure what virtue you're trying to signal here. Just because someone used the limited funds they had available to obtain the software and educational resources they were interested in, they've exercised some sort of inappropriate privilege? Isn't that the whole idea behind college? Spend money to learn cool stuff?

Ok, I'll spell it out. Presenting the idea that MuJoCo having a license fee rather than being free is better, not worse, or even that the difference doesn't matter because "well, I paid for stuff" is the inappropriate part of the privilege. Given a choice between "I can learn X but I need to spend significant money on it" and "I can learn X for free", with everything else equal arguing for the former is exclusionary.

with everything else equal arguing for the former is exclusionary.

Sure. But who argued for that? They merely pointed out that they considered this particular physics engine worth spending money on. The implication was that because money is typically limited for a college student, the software must really be worthwhile. The implication was not "LOL, you must be broke and can't afford good software."

Re: Open-sourcing the MuJoCo physics simulator for robotics

#76

Post by regularfry »

CamperBob2 wrote: post #75
regularfry wrote: post #73

Earlier quoted context omitted.

Ok, I'll spell it out. Presenting the idea that MuJoCo having a license fee rather than being free is better, not worse, or even that the difference doesn't matter because "well, I paid for stuff" is the inappropriate part of the privilege. Given a choice between "I can learn X but I need to spend significant money on it" and "I can learn X for free", with everything else equal arguing for the former is exclusionary.

with everything else equal arguing for the former is exclusionary. Sure. But who argued for that? They merely pointed out that they considered this particular physics engine worth spending money on. The implication was that because money is typically limited for a college student, the software must really be worthwhile. The implication was not "LOL, you must be broke and can't afford good software."

The implication j was responding to was "if you really cared, a mere few hundred dollars wouldn't matter because you'd be able to find the money." If you don't read that into the message chain, fine, but I do.

Re: Open-sourcing the MuJoCo physics simulator for robotics

#77

Post by CamperBob2 »

Animats wrote: post #72

The demo object that turns itself over is nice. I used to use a rattleback as a test back when I was working on accurate but slow physics engines in the 1990s. That's an ellipsoid cut by a plane that isn't axis-aligned. You spin it, and it spins, stops, rocks, and spins a bit in the other direction. Very similar to what they're doing. The key to this is a multi-point contact model. If your contacts are single points,…

It's hard to do it if some asshat patents it, that's for sure. At least in commercial applications.
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