[ODE] Mass and trimesh collisions

Patrick McColgan patrick at torcinteractive.com
Tue Jan 25 12:01:14 MST 2005

Thanks for the replies, no success yet though.

I increased the quickstep solver iterations from the default 20 to 1000 
and it appeared to make no significant difference, I also reduced the 
CFM from the already tiny default of 1e-10 to 0.0 and again saw no great 
changes.  As I said before setting the ERP to 1.0 prevents full 
penetrations on walls but not when the body falls, the body will hit a 
surface falling with a greater velocity.  I don't particularily want to 
have the ERP full anyway.

Megan, the level is indeed a trimesh and my maximum contacts has always 
been four.  When the body collides with walls it generates 2 contact 
points generally and when it fall on the ground it makes 4 so I did 
increase the number and check but I don't really see it as an issue just 
now, perhaps in the future.

As far as I can see the simulation just can't compensate for the 
momentum of the body, I'm not sure if I have any say in that at set up 
but what I'm looking at now is the dependancy on mass and velocity to 
generate contact forces.

Any ideas and advice are appreciated.

Gerritt Brownlee wrote:

> Did you try lowering the CFM?  Or using more iterations per frame, 
> which is different from step size. for example with quickstep:
>   dWorldSetQuickStepNumIterations (world, 15);
>   dWorldQuickStep (world,0.04);
> >Hello
> > >I've been working with ODE to implement a character controller, it 
> >has progressed well however I had been using a cyclinder with a 
> >total mass of 5 units and when I changed the total mass to a more 
> >realistic 80 I found that the avatar (moving at around 2.5 units per 
> >second) started to move through walls and when falling would fall 
> >through floors. > >The collisions do register, they do apply a force 
> in the right >direction which slows the avatar but as I have been 
> stepping through >the program it appears that it just isn't scaling 
> the force enough >despite apparently using the mass and inverse mass 
> in calculations.   >Using the joint feedback function I get a force of 
> about 528 units >twice and I think I need a force of around 12, 000. > 
> >Has anyone else experienced this, or is this a known issue?  I had a 
> >look in the archive but there is very little on it, more seems to be 
> >on mass ratios problem between two bodies.  Is there a limiting 
> >parameter with regards to mass in collisions? > >Setting the ERP to 
> one helped on walls but not floors and the >program is stepped at 
> about 1/60 hz although I did try it at 1/100 >but it made no 
> difference. > >Thanks >_______________________________________________ 
> >ODE mailing list >ODE at q12.org >http://q12.org/mailman/listinfo/ode
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