Java-Gaming.org
 Featured games (81) games approved by the League of Dukes Games in Showcase (497) Games in Android Showcase (114) games submitted by our members Games in WIP (563) games currently in development
 News: Read the Java Gaming Resources, or peek at the official Java tutorials
Pages: [1]
 ignore  |  Print
 ODEJava damping  (Read 1242 times) 0 Members and 1 Guest are viewing this topic.
Matt2000

Senior Newbie

Let's all help Java not suck.

 « Posted 2004-02-19 20:41:27 »

Just in case anyone's interested I found that it was possible with certain types of collisions to get an object moving with such great angular momentum that the simutlation eventually clamped the value and turned off physics for the object.  This looks like the object just freaks out and fires off screen after a couple collisions or so.

In any case, I read a little on the ODE mailing lists to see how to do linear and angular damping and they simpy suggested a very small impulse in the opposite direction of each velocity.  So I ended up with this slightly lame method to apply damping wich you can call per step:

 1  2  3  4  5  6  7  8  9  10  11  12  13  14 `private void applyDamping() {    for (int i = 0; i < bodies.size(); i++) {        Body body = (Body) bodies.get(i);        Vector3f linVel = new Vector3f(body.getLinearVel());        linVel.negate();        linVel.scale(0.0001f);        body.addForce(linVel);        Vector3f angVel = new Vector3f(body.getAngularVel());        angVel.negate();        angVel.scale(0.000001f);        body.addRelTorque(angVel);    }}`

Those lovely numbers I'm scaling by are simply the result of trying out a bunch of different values, these seem to work fairly well for the masses I'm using.

Matt
Jani Laakso

Junior Member

Do it with Java!

 « Reply #1 - Posted 2004-02-20 04:12:18 »

Quote
Just in case anyone's interested I found that it was possible with certain types of collisions to get an object moving with such great angular momentum that the simutlation eventually clamped the value and turned off physics for the object.  This looks like the object just freaks out and fires off screen after a couple collisions or so.

Good going!

Yes, also you get bunch of LCP error messages usually at this stage. That damping is usually something that occurs with geoms that do not have well concentrated mass, e.g. long narrow boxes tend to spin off widly. I assume you get similar problems if you play too much with the inertia matrix.

Actually the "right" way to reduce this problem is this:

void dBodySetFiniteRotationMode (dBodyID, int mode);

This function controls the way a body's orientation is updated at each time step. The mode argument can be:

* 0: An ``infitesimal'' orientation update is used. This is fast to compute, but it can occasionally cause inaccuracies for bodies that are rotating at high speed, especially when those bodies are joined to other bodies. This is the default for every new body that is created.
* 1: A ``finite'' orientation update is used. This is more costly to compute, but will be more accurate for high speed rotations. Note however that high speed rotations can result in many types of error in a simulation, and this mode will only fix one of those sources of error.

Quote

In any case, I read a little on the ODE mailing lists to see how to do linear and angular damping and they simpy suggested a very small impulse in the opposite direction of each velocity.  So I ended up with this slightly lame method to apply damping wich you can call per step:

This is something that most simulations would need, unless you want your simulation to run in void (space) without any friction like air has, so I'd say your damping codebit is usefull for all users.

Cheers!
Pages: [1]
 ignore  |  Print

You cannot reply to this message, because it is very, very old.

 Add your game by posting it in the WIP section, or publish it in Showcase. The first screenshot will be displayed as a thumbnail.
 BurntPizza (24 views) 2014-09-19 03:14:18 Dwinin (39 views) 2014-09-12 09:08:26 Norakomi (67 views) 2014-09-10 13:57:51 TehJavaDev (93 views) 2014-09-10 06:39:09 Tekkerue (47 views) 2014-09-09 02:24:56 mitcheeb (68 views) 2014-09-08 06:06:29 BurntPizza (51 views) 2014-09-07 01:13:42 Longarmx (38 views) 2014-09-07 01:12:14 Longarmx (44 views) 2014-09-07 01:11:22 Longarmx (40 views) 2014-09-07 01:10:19
 BurntPizza 37x Riven 18x Rayvolution 18x ags1 16x princec 16x basil_ 16x KevinWorkman 15x LiquidNitrogen 12x kevglass 12x theagentd 11x nsigma 11x deathpat 10x HeroesGraveDev 9x The Lion King 7x Gibbo3771 6x cylab 6x
 List of Learning Resources2014-08-16 10:40:00List of Learning Resources2014-08-05 19:33:27Resources for WIP games2014-08-01 16:20:17Resources for WIP games2014-08-01 16:19:50List of Learning Resources2014-07-31 16:29:50List of Learning Resources2014-07-31 16:26:06List of Learning Resources2014-07-31 11:54:12HotSpot Optionsby dleskov2014-07-08 01:59:08
 java-gaming.org is not responsible for the content posted by its members, including references to external websites, and other references that may or may not have a relation with our primarily gaming and game production oriented community. inquiries and complaints can be sent via email to the info‑account of the company managing the website of java‑gaming.org