Search found 85 matches

by DannyChapman
Thu Jun 05, 2008 9:23 am
Forum: General Bullet Physics Support and Feedback
Topic: center of mass not at mesh origin
Replies: 13
Views: 28438

Re: center of mass not at mesh origin

That said, I agree it would be nice to be able to set center of mass on an object - but I can't think of any pratical use for doing so when the intent is to render images based off the physics data. There's lots of uses - e.g. 1. Artists may want to set the origin of models at ground level - e.g. l...
by DannyChapman
Thu Mar 13, 2008 11:55 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Angular spring damping
Replies: 6
Views: 4508

Re: Angular spring damping

Make it apply to the angle between 3 points - so if you have three points A-B-C then whatever force you apply to C, you apply to A in the opposite direction. In fact, you could actually distribute the "opposing" force over multiple other points. I realised later this is wrong :oops: as it does intr...
by DannyChapman
Wed Mar 12, 2008 6:23 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Angular spring damping
Replies: 6
Views: 4508

Re: Angular spring damping

Make it apply to the angle between 3 points - so if you have three points A-B-C then whatever force you apply to C, you apply to A in the opposite direction. In fact, you could actually distribute the "opposing" force over multiple other points.
by DannyChapman
Fri Mar 07, 2008 10:11 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Constraint-Based Verlet Physics Engine
Replies: 20
Views: 11130

Re: Constraint-Based Verlet Physics Engine

My experience is: The Vertlet/particle method for rigid bodies is super-simple to get some simple demos running. However, as soon as you start adding the features that are needed to make it useful - friction, controlled collision restitution, complex shapes etc you end up with so many hacks it becom...
by DannyChapman
Fri Feb 15, 2008 10:27 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Physics for Phun
Replies: 9
Views: 7227

Re: Physics for Phun

This is very nice and fun to play/experiment with. However, I did create a "Newton's Cradle" - 5 balls suspended on highly-damped/strong springs, initially at rest, side by side, and touching each other. When one is dragged to one side, it bounces off the 4 other balls, rather than propagating the s...
by DannyChapman
Mon Dec 17, 2007 11:29 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Physics and Lowpassing
Replies: 8
Views: 2746

Re: Physics and Lowpassing

I use local space positions too and it works fine and is very simple. Also, I woke up this morning thinking how trivial it would be to use this to add an additional position based friction constraint that would be enabled when you detect that static friction _should_ be preventing movement (even tho...
by DannyChapman
Thu Dec 06, 2007 10:15 am
Forum: General Bullet Physics Support and Feedback
Topic: Any decent tutorial on making a Vehicle work with Bullet?
Replies: 4
Views: 4021

Re: Any decent tutorial on making a Vehicle work with Bullet?

You could also look at the demos for other physics libraries, since the demo code will normally be open source even if the physics library itself isn't. There's a "raycast" car with my jiglib (http://www.rowlhouse.co.uk/jiglib, also search for jiglib and jigglex on youtube) that is quite fun to driv...
by DannyChapman
Tue Dec 04, 2007 5:51 pm
Forum: General Bullet Physics Support and Feedback
Topic: Character Controller
Replies: 5
Views: 3304

Re: Character Controller

When you're on a sideways slope the contact point is to one side of the sphere centre. Perhaps when you then move forward, since the ground friction is applied to one side of the sphere centre, it results in a torque around the vertical axis, so your character rotates. Often character controllers ar...
by DannyChapman
Thu Oct 18, 2007 11:18 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Newton's cradle
Replies: 8
Views: 8885

Re: Newton's cradle

If you build the LCP based on Newton's restitution law then you get an unphysical result when you apply it to more than 2 bodies in simultaneous collision because the law is an empirical result of a collision between 2 bodies only. There are collision laws for more than 2 bodies, apparently, but I g...
by DannyChapman
Mon Jan 08, 2007 10:17 pm
Forum: Non-technical forum and license/patent discussion
Topic: Equivalence sequential impulses & Projected Gauss Seidel
Replies: 22
Views: 51465

It is typical to mix a direct LCP solver with iterative method. Especially high speed Ragdolls don't behave well on impact, their limbs detach. Typical scenario is a high speed car against a pedestrian, or a character standing next to a barrel (explosion). I've seen this in a game I worked on in th...