[ODE] skeletal character

[Jani Laakso]

alfo trentam wrote:

> Someone knows how to implement a skeletal character system which make 
> possible to animate a character (run, walk, fight, and so), letting 
> fall like a rag doll and, after some seconds, make it rise animating 
> it again?
> Suggestions are welcome, I don't pretend a full working source code!

Perhaps it might be good to start with basics. Define simple rag doll 
consisting of
-head (sphere)
-neck (CCylinder)
-torso (Box)
-left upper arm (CCylinder), left lower arm (CCylinder), hand (Box)
-right upper arm (CCylinder), lower arm (CCylinder), hand (Box)
-left upper leg (CCylinder), lower leg (CCylinder), foot (Box)
-right upper leg (CCylinder), lower leg (CCylinder), foot (Box)

Make it e.g. with 3d Studio and export it in a format that your 
application can read. Then after ODE has objects created and positioned 
in right place, attach joints to each objects. Experiment with the 
parameters and after your rag doll interacts with other objects good 
enough, start wondering how to make it do actions (walk, sit etc.).

This is all very simple, but can anyone at least share a code (any 
language) that has an example of human body consisting of boxes, 
cylinders and an sphere with joint definitions? I am especially 
interested of joint definitions, what joints are you using and with what 
kind of parameters. I have made an application using Xith3d (Java) + 
odejava (ODE bindings for Java) and it's fun, but takes time to adjust 
all parameters in such way that my rag doll falls and takes hits in 
realistic way..

Making your human body to do actions is another topic that I'd like more 
information as I'd assume that there is no particularly easy way to do 
this in a realistic way. I'd assume that one does not try to simulate 
complex human body actions through ODE's methods (very complex), but to 
make your human body to animate e.g. walking motion as long as ODE 
permits it. At least on games the middleway should be appropriate. In 
other words do it the wrong way by defying physics and set your body to 
new position and angle unless an collision occurs. I'd think that if you 
stand, walk, sit or do other 'deterministic' actions, you do them in the 
old fashioned way, like you would do without ODE. But if an special 
event occurs, e.g. your body collides with an bullet, car or you fall 
from a roof then you instantly switch control back to ode and simulate 
your 'incident' realisticly up to a certain point. After the 'incident' 
you switch back to old fashioned style. This is only speculation and 
simplified description, I hope mailing list readers now fix my 
assumptions and share their ideas..

PS. Be sure to check http://odejava.dev.java.net www-pages. It has three 
3d demos also (windows bat scripts included). Odejava supports almost 
all the aspects of ODE (it works very well on Java), but e.g. trimesh 
API is still missing from the java side.

-- 
Jani Laakso / IT Mill Ltd | Tel. +358 40 5898086 | http://www.itmill.com