[ODE] Some objects pass through other objects

[Keith Wiley]

On Nov 13, 2005, at 6:40 PM, Jon Watte (ODE) wrote:

>
>> chain to represent the sling with a pouch in the middle.   
>> However,  I haven't learned how to use trimeshes in ODE yet, so my  
>> pouch is  actually a few links in the middle of my chain that are  
>> wider than  the
>
> Trimesh-to-trimesh collisions are not very robust; I recommend  
> against modeling the chain links as actual links. Instead, I would  
> model it as a series of bodies linked with universal joints, and  
> model the chain collision as a series of ccylinders. I'd also make  
> the model much coarser than the rendered representation -- maybe  
> five links between the axle and the pouch.

Sorry for the confusion, that's what I meant by links.  My chain is  
an end to end series of short poles (well rectangular, not  
cylindrical) connected by ball joints.  I wonder if universal joints  
would have any advantage.  I guess with now the chain collisions are  
block collisions since the links are long thin blocks, not  
cylinders.  I only did that on the assumption that it would speed  
things up (fewer triangles).  I'll have to try it with cylinders  
too.  It is fairly course right, about five links as you said,  
although I render it the same way that it is modeled, so it doesn't  
look like a rope.  I'm not sure how I would render it more smoothly  
though.  Even if I had multiple small links to render, I would only  
have position/orientation info on the modeled links.  Perhaps I could  
interpolate between them or something.  That seems possible.

> In general, it's important to not get too tied down in details of  
> how you would build your thing in real life, but instead think of  
> the simplest, most robust arrangement of primitives that will  
> accomplish the simulation goal you're after.
>
> This is somewhat mentioned in the documentation and FAQ, but not at  
> all in the amount of detail that someone new to game physics  
> simulation would need to be able to absorb it.

Thanks for the tip.  The model is really great at the moment  
actually.  I'm going to turn it into a simple little game at some point.

Cheers!

________________________________________________________________________
Keith Wiley         kwiley at cs.unm.edu         http://www.unm.edu/~keithw

"Luminous beings are we, not this crude matter."
                                            --  Yoda
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