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  New Version of Phys2D  (Read 7389 times)
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Offline CommanderKeith
« Reply #30 - Posted 2007-03-02 03:39:27 »

That looks amazing, well done, really impressive. 

I can't wait to see it in action!

Offline gideon

Senior Newbie





« Reply #31 - Posted 2007-03-06 23:43:17 »

A small update: I am still working on the collision detection, it's mostly a long and painfull process of debugging. There are quite a lot of problems with floating point rounding errors which are not easy to solve. While many examples work perfectly, like the gear system I showed before, however some simple examples exhibit very strange (jumpy) behaviour.

Movable line support is coming along nicely, although I will have to seriously alter the collision detector's structure to properly implement line-line collisions and allowing one way pass-though lines. For both problems, I need to know on what side (of a line) the other body was in the last frame. Just making the collision detector statefull isn't enough; it will have to be updated each frame as well. But I'm talking to myself.

Currently I'm planning to
- get the most apparant bugs fixed or work around them
- get movable line support working except for line-line collisions and pass-through lines
.. and release a patch. After that I'll continue with optimizations and getting the line-stuff working, but that will be another patch.

I still update my project's svn fairly regularly: http://sourceforge.net/svn/?group_id=117163, in case you can't wait any longer.

The towship's adventures
Offline darkprophet

Senior Member




Go Go Gadget Arms


« Reply #32 - Posted 2007-03-07 04:49:38 »

Sorry to state this if you already knew, but you could do all your calculations as doubles then cast the result...I know Intel FPUs have 80bit precision so a double takes roughly the same time as a float to calculate (there are a few other issues).

DP

Friends don't let friends make MMORPGs.

Blog | Volatile-Engine
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Legends of Yore - The Casual Retro Roguelike
Offline gideon

Senior Newbie





« Reply #33 - Posted 2007-03-07 10:45:49 »

Using doubles only makes the problem more rare: very small penetrations will simply always be there, I have to deal with them some way or another.

The towship's adventures
Offline Marvin Fröhlich

Senior Member




May the 4th, be with you...


« Reply #34 - Posted 2007-03-07 20:59:01 »

Using doubles only makes the problem more rare: very small penetrations will simply always be there, I have to deal with them some way or another.

Did you check the performance impact of using doubles instead of floats? (Of course correctness should be of higher priority than performance.)

Marvin
Offline gideon

Senior Newbie





« Reply #35 - Posted 2007-03-07 23:22:11 »

(Of course correctness should be of higher priority than performance.)

Why should it? As long as everything looks 'natural' I'm ok with it. In any case, I haven't had any need for doubles yet; the problems that I encounter are usually more related to picking the right collision normal and penetration depth.

There might be some trouble up ahead though. I haven't properly tested the accuracy yet, for example placing object very far from the origin and using very small objects. Most certainly things will go wrong somewhere, if it turns out we need more 'space' (determined by the minimum objects size and maximum distance from the origin) switching to floats isn't really big a deal.

Maybe fixed point math could be useful. Does anyone know whether fixed point math actually is faster than floating point math? On modern processors like my dual core amd64 it's probably completely irrelevant, but what about mobile processors?

The towship's adventures
Offline darkprophet

Senior Member




Go Go Gadget Arms


« Reply #36 - Posted 2007-03-08 03:21:47 »

fixed point is faster on mobile phones than floating point. IIRC, a few games use fixed point to accelerate 3D rendering on the NGage platform.

DP

Friends don't let friends make MMORPGs.

Blog | Volatile-Engine
Offline t_larkworthy

Senior Member


Medals: 1
Projects: 1


Google App Engine Rocks!


« Reply #37 - Posted 2007-03-08 10:35:36 »

I checked out Phys2D yesterday with the idea of intergrating it with JOODE. It looks really nice, but at the moment there are not really enough new 2D primatives to really warrent the work. So just waiting for polgon support... hehe. I would personally like accuracy to be there, with a switch to turn it off, though our tri mesh support also has problems with very pointy thin geometies (ported from Collada I think).
Tom

Runesketch: an Online CCG built on Google App Engine where players draw their cards and trade. Fight, draw or trade yourself to success.
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