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# h4tt3n

Member Since 02 Apr 2008
Offline Last Active Yesterday, 08:55 AM

### In Topic: Problem vehicle suspension formula - If damperForce is >0 then the vehicl...

17 October 2016 - 11:38 PM

I thin it's simply a sign error.

```float suspensionForce = stiffness * contactDepth + dampingForce * contactSpeed;
```

The above line should really have been:

```float suspensionForce = - stiffness * contactDepth - dampingForce * contactSpeed;
```

Cheers,

Mike

### In Topic: Position Based Fluids smoke and fire

17 October 2016 - 11:34 PM

It's very difficult for us to say without having seen any of your code. It's all in the kernels and in tweaking variables. Also, I have reduced instability along the edges in my simulations by "softening" them up; rather than force the particles to stay inside the container by manipulating their position directly, treat the edge as a spring that will allow the fluid to expand a little beyond it when pressure builds up.

Cheers,

Mike

### In Topic: How does Runge-Kutta 4 work in games

06 June 2016 - 02:13 PM

What about manual capping? What if I ensured that the damping never exceeds more force than needed to get object exactly at it's rest position? And for spring to ensure that the force never exceeds the force needed to push it to the other side of the rest length point at the same distance? Is this kind of good idea?

I wrote an article about improving spring stability with simple math. It might be of help to you. My next article presenting even better springs is on its way.

http://www.gamedev.net/page/resources/_/technical/math-and-physics/towards-a-simpler-stiffer-and-more-stable-spring-r3227

### In Topic: How does Runge-Kutta 4 work in games

06 June 2016 - 06:37 AM

Don't use RK4 in games. It is not symplectic, which means that it doesn't conserve enery. Also, I believe that like other higher order integators, it behaves poory with velocity dependent movement. Use symplectic Euler /semi-implicit Euler (at smaller timestep) instead. If you need the high accuracy, instead use David Whysong's excellent integrators that have 4th, 6th, and 8th order accuracy.

### In Topic: Destructiblity: 2D voxel (okay, pixel) physics

03 April 2016 - 12:50 PM

Do you know Cortex Command from Data Realms? It has some very nice pixel physics going on - maybe if you contact them, they will let you in on their methods?

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