Search found 803 matches

by ewjordan
Wed Dec 15, 2010 5:31 am
Forum: Java
Topic: are thread-local variables really all that fast
Replies: 6
Views: 1663

Re: are thread-local variables really all that fast

If I had to guess, I'd say that thread locals are almost certainly not the optimal solution here, storing the objects per-world is probably going to be quite a bit faster. My gut says that the thread lookup is actually the slowest part of that operation, though I could be wrong. The problem, of cour...
by ewjordan
Mon Nov 15, 2010 7:00 pm
Forum: Java
Topic: Background Image
Replies: 2
Views: 2650

Re: Background Image

You seem to have figured it out - all the image handling stuff in the testbed is done through Processing, so check the docs there at http://processing.org/reference/ for info on the various methods.
by ewjordan
Fri Nov 05, 2010 9:20 am
Forum: Flash
Topic: Flash to Java port of this code (maybe getTransform)
Replies: 1
Views: 861

Re: Flash to Java port of this code (maybe getTransform)

Vec2 ldirection = wheel.getXForm().R.col2.clone(); ldirection.mulLocal(engineSpeed); If you're using a different version of JBox2d, it's possible it might be getTransform instead of getXForm. Are you using Eclipse/Netbeans/IntelliJ? You should be able to get autocompletion, and browse through the p...
by ewjordan
Wed Oct 20, 2010 6:33 pm
Forum: General Discussion
Topic: Move a body from point A to point B in T time
Replies: 2
Views: 1116

Re: Move a body from point A to point B in T time

The formula you need is x(t) = x(0) + v(0)*t + .5 (F/m) * t^2

Solving for F, and writing the equation for y, too:

Fx = (x(t) - x(0) - vx(0)*t) * 2m/t^2
Fy = (y(t) - y(0) - vy(0)*t) * 2m/t^2

I think...might want to check my math, though.
by ewjordan
Fri Oct 15, 2010 11:59 pm
Forum: General Discussion
Topic: Changing a body from dynamic to static
Replies: 9
Views: 1820

Re: Changing a body from dynamic to static

That (http://bit.ly/bO2IW0) is an awesome effect, fantastic idea! I'll take a look through your code at some point soon; it's nice to have independent confirmation of the bug, the codebase I discovered it in was complex enough that I couldn't really be sure it wasn't something else going on. I'm sti...
by ewjordan
Fri Oct 15, 2010 10:52 am
Forum: General Discussion
Topic: Changing a body from dynamic to static
Replies: 9
Views: 1820

Re: Changing a body from dynamic to static

There are still a few bugs in the AS3 port, particularly related to continuous physics and the way it interacts with the solver, which cause trouble even when bodies are not bullets (probably caused by the fact that CCD is always active for non-bullets against static objects). It may be that its goi...
by ewjordan
Thu Oct 14, 2010 2:43 am
Forum: Build Issues
Topic: cmake didn't generate xcodeproj file
Replies: 9
Views: 3984

Re: cmake didn't generate xcodeproj file

Here's the exact list of commands that work for me, starting from scratch just now. 0) cd (wherever you like to put code) 1) svn checkout http://box2d.googlecode.com/svn/trunk/ box2d-svn (lots of output snipped) ...Checked out revision 141. 2) cd box2d-svn/Box2D/Build 3) cmake -DBOX2D_INSTALL=ON -DB...
by ewjordan
Wed Oct 13, 2010 12:33 pm
Forum: Build Issues
Topic: cmake didn't generate xcodeproj file
Replies: 9
Views: 3984

Re: cmake didn't generate xcodeproj file

cmake -DBOX2D_INSTALL=ON -DBOX2D_BUILD_SHARED=ON -G Xcode ..

is what you want, I think.

Might have to delete the cache file before it will run, if it's already generated the Unix makefiles.
by ewjordan
Wed Oct 13, 2010 12:14 pm
Forum: General Discussion
Topic: Conservation Laws Under Constraint Violation
Replies: 2
Views: 789

Re: Conservation Laws Under Constraint Violation

Okay, if that's to be expected, then that's fine - I don't actually need such large structures, I just found it curious that they blew up like that.

Will see if I can put together a testbed example later today, though, just to show you what's going on.
by ewjordan
Wed Oct 13, 2010 3:06 am
Forum: General Discussion
Topic: Conservation Laws Under Constraint Violation
Replies: 2
Views: 789

Conservation Laws Under Constraint Violation

Mostly a question for Erin. While trying to track down (what I now think is) a CCD bug in the Flash port, I've been testing against Java (easier to check AS3 code vs. Java than C++) and building some rather large structures lately, tall triangle scaffoldings composed of many rods and joints, and one...

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