Cursor Gravity

#1

Post by kirubakaran » Mon, Mar 16, 2009, 5:10 AM UTC

Re: Cursor Gravity

#2

Post by paulbaumgart » Mon, Mar 16, 2009, 5:53 AM UTC

It's surprisingly fun for such a simple little thing, especially since the lack of friction makes it so much more compelling than the "marble in a bowl" demonstration I got when I was a kid.

Re: Cursor Gravity

#3

Post by newt0311 » Mon, Mar 16, 2009, 6:44 AM UTC

Howto for orbits: This is a closed system so the only energy that can possibly be added into the system is from your movement of the cursor. So keep the cursor far away from the planet until it hits about center and then move the cursor close but so that the planet slingshots around it. This should establish a stable orbit. If you are careful enough, the orbit will stay in the screen.

PS. Checked the physics. Seems fine as its just standard Newtonian.

Re: Cursor Gravity

#4

Post by aristus » Mon, Mar 16, 2009, 7:19 AM UTC

I used to do this with a large magnet and a little chip off the magnet... accidentally figured out how orbits work. Fun times. :)

Re: Cursor Gravity

#5

Post by tome » Mon, Mar 16, 2009, 9:00 AM UTC

He's used the Euler method, which I think is why you get aberrant behaviour when the cursor comes near the particle:

http://en.wikipedia.org/wiki/Euler's_method#Error

Re: Cursor Gravity

#6

Post by extension » Mon, Mar 16, 2009, 9:36 AM UTC

This also serves as a good repro of a Firefox memory leak (watch your task manager while it's running). There won't be many usable canvas apps until their JS engine is tightened up or replaced.

Re: Cursor Gravity

#7

Post by pmjordan » Mon, Mar 16, 2009, 9:52 AM UTC

Nice little toy, but what's the next level? 2 objects, try to get a stable orbit? Talk about a steep difficulty curve. (http://en.wikipedia.org/wiki/N-body_problem)

Re: Cursor Gravity

#8

Post by [deleted] » Mon, Mar 16, 2009, 10:28 AM UTC

extension wrote: post #6

This also serves as a good repro of a Firefox memory leak (watch your task manager while it's running). There won't be many usable canvas apps until their JS engine is tightened up or replaced.

[deleted]

Re: Cursor Gravity

#9

Post by allocativeeffic » Mon, Mar 16, 2009, 12:06 PM UTC

extension wrote: post #6

This also serves as a good repro of a Firefox memory leak (watch your task manager while it's running). There won't be many usable canvas apps until their JS engine is tightened up or replaced.

No, it gcs after a while. Memory usage steadily climbs until it hits a certain point and then drops back down.

Re: Cursor Gravity

#10

Post by ilaksh » Mon, Mar 16, 2009, 12:09 PM UTC

Would work fine in IE if he just added the ExplorerCanvas js file (from Google) http://excanvas.sourceforge.net/