[ODE] several questions from new user
Martin C. Martin
martin at metahuman.org
Mon Jan 26 20:17:17 MST 2004
Ary Setijadi Prihatmanto wrote:
> 1. I tried to make capped-cyllinder chains (only like chain sample just
> with capped cyllinder element) with zero forces on it (free fall
> movement). When the body hit the ground, I noticed that the geoms
> sometimes overlap each other. I try to adjust global ERP and CFM but it
> seems the results in not change. How can I solve the problem.
I think you can't solve the problem. ODE doesn't try to force geoms
apart until they've collided. So you'll always have some overlapping,
at least for a little while. Also, if ERP < 1, they may overlap in
steady state. Although, if you don't have gravity, then probably not.
> 2. I want to make a system with a complex visualization but still with
> simple physical simulation & collision detection. Making a visualization
> as a puppet of physical simulation. For that purpose, I think i will
> going to need joint information especially if we want to use
> skeleton-based mesh. There are methods available for hinge, hinge-2 and
> slider joint types, but not for ball and universal.
> I realize that it is not trivial to get the angle change for ball and
> universal joint, but maybe relative transformation matrix between
> attached bodies will be usefull to get (with jointID parameter) not only
> global transformation matrix(function with GeomID/BodyID parameter).
Sure the universal joint does, although you might need to get the latest
version from CVS. For ball and socket, try attaching an AMotor to it,
with FMAX = 0. You can read the joint angles from the AMotor (I think).
> 3. I also want to have a physical simulation only a part of the body
> system and make it fix for other part for several simulation periods.
> I know it is possible to disable the simulation for the whole "island",
> but is there any way to do the similar for the part of the island?
> I dont want to ruin my ODE copy ^_^
I think this is answered in the fact. You can have a joint or motor
between the part you want fixed & the world.
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