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# Irlan Robson

Member Since 08 May 2012
Online Last Active Today, 05:12 AM

### Bounce v1.0 Release

24 July 2015 - 12:51 PM

Good afternoon everyone.

I'm happy to distribute Bounce, a lightweight and portable 3D physics engine for games.

Bounc3 is available at GitHub.

https://github.com/irlanrobson/Bounce

Some of the physics engine features can be seen at the basic (.pdf) documentation, living inside the repository. Additionaly, a demo application lives inside the repository as well.

Cheers,

Irlan R.

### Adding restitution to the MLCP

24 May 2015 - 08:22 AM

The compl. cond. for the contact and impact in a vel. based formulation is:

Ju(t + dt) + eJu(t) >= 0 _|_ lambda >= 0.

where u = system velocity, and J is the normal jacobian, e is the coefficient of restitution.

My question is:

Using an error correction term b, the condition becomes:

Ju(t + dt) + eJu(t) + b >= 0 _|_ lambda >= 0

?

So, defining low = 0, high = infinite, passing thourgh all simplification, assuming acceleration = ( u(t + dt) - u(t) ) / dt, we have

A = J*M^-1*J^T,

x = dt*Lambda

b = J * ( u(t)+dt*M^-1*f) + eJ*u(t) + b, (f == external forces),

w = Ax - b _|_ low <= w <= high,

?

### 3D SAT Problem

10 April 2015 - 07:55 PM

Hello, newbie to SAT algorithm.

What am I missing in the SAT implementation below?

http://pastebin.com/CqNbB7ph

I think the problem is between the edge-edge case. Code doing all computations in world-space.

### Graphs tool for a thesis (needing an suggestion)

13 March 2015 - 10:20 AM

I need a graphs tool to write my graduation project. I'm writing a rigid body simulation so I need to graph the Euler and RKs methods. I would like to know if there is one which I can do this fast. A free software if possible.

### Friction Impulses (boxes are sliding on the ground)

09 February 2015 - 08:07 AM

Hi.

The problem I'm facing with is with correct impulses but wrong behaviour. The physics engine uses split-impulses (bias-velocities), but when objects fall over a plane it starts to slide like if there was an joint above them. Here's a video:

[This video was deleted because was messing up with my channel, but it is what the description says]

The loop (at 60HZ = 0.016ms):

Update contact positions (contact caching not implemented yet, so skip it);

Check for collisions;

Apply forces (integrate velocities);

Prepare constraint data (normal inverse mass, two tangents inverse mass, and bias values);

Warm Start last frame impulses (contact caching not implemented yet, so skip it)

Apply Contact Constraint Impulses (10 iterations, zero accumulated bias impulse, etc.);

Apply velocities (integrate positions, zero bias velocities);

I'm skiping the warm start, but that doesn't mean that I should get the behaviour above.

Has anyone faced with that problem?

Here's the overview of each task:

http://pastebin.com/K1iF06nH

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