Virtual World timing depends on your pc?
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Author:  customwebprogrammer [ Mon Sep 26, 2011 11:32 am ]
Post subject:  Virtual World timing depends on your pc?

First off, the FTC Bowled Over competition arena is fantastic! What a super way for our team to try out RobotC at home, or when the Tetrix bot is still under construction!

A buddy and I are emailing code back and forth for the FTC Bowled-Over VW. He created a quick demo that comes down the ramp, turns, and pushes the bowling ball into the front parking zone. His demo uses all timed movements, like motor on, waitMsec(3000); motor off.

When I run his demo on my laptop, the robot does move, but barely gets halfway down the ramp before the program ends! He built the demo on a nice desktop, and my laptop is a minimalist Centrino 1.6MHz. I suspect that it just runs so slow on my laptop that the timing stops the motors way too early.
We've rewritten our quick demo to use encoders, and are now in the process of sharing that. But I'm left with the question: is motion timing processor-dependent?

Author:  Ed Paradis [ Mon Sep 26, 2011 11:47 am ]
Post subject:  Re: Virtual World timing depends on your pc?

I suspect your machine doesn't meet the minimum requirements, unfortunately. Motion timing and overall physics performance will suffer greatly if your machine cannot run the simulation at full speed.

Essentially what happens is that physics simulation "frames" get skipped if the computer isn't fast enough to process them. Then you end up with an incomplete approximation.

So, yes, it ends up being processor-dependent, but only if your machine can't run the simulation fast enough. I also suspect that you won't get very repeatable results on an underpowered machine because which frames get skipped is essentially random. Once the simulation is running at full speed, it will be the same on all machines.


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