Rigid Body Weights and Ragdoll Armatures.

Hi all

I have a couple of quick questions regarding rigid bodies.

My first question is regarding the mass of objects.

I have a model I’m working on at the moment which has heavy wooden blocks being suspended by lightweight cotton or string.
The cotton is made using a chain of rigid body blocks joined at the ends. I need to suspend the wooden blocks from the cotton without the cotton affecting the movement of the blocks until it is completely tense. Also, the cotton needs to be completely inelastic. I’ve demonstrated this in the attached pictures, they show heavy and light blocks each suspended from seperate fixed points. One image shows how I need it to work, the heavy blocks hanging straight down, unnafected by the chain until completely outstretched. The other image shows what happens when the mass of the ojects is equal, the lightweight chain sags, pulling the heavier blocks in (not what cotton would do to wood). I thought it would as simple of upping the mass on the blocks but this makes the joints of the cotton stretch an amazing amount.

Is there any way I can make the mass of the objects drastically different but have rigid body joints completely inelastic? I can’t imagine this wouldn’t be possible, I should think I am just looking in the wrong places.

My second question is about rigid bodies affecting armatures. I’ve read many posts that say rigid bodies on armatures don’t work, but I’ve also been directed to this post, which has a ragdoll bear moving an armature. I can’t work out how this is done, could anyone please help me figure this out? I don’t need a ragdoll armature in-game, just a baked ragdoll movement to then use in an animation.

If anyone could help me out with either of these questions I really would appreciate it!

while the sumo engine (the one that is now depricated) seems to have gotten an name for Blender when used for scientific simulation, the Bullet engine 2.0 (as it exists in the current stable release) is not quite so precise. At the moment, we’re all waiting for the next release of Blender (2.45+) which has updated the Bullet engine to ver. 2.5 and looks to be a much more comprehensive integration.

The bit of the release candidate that I’ve seen shows rigid body joints and dynamic material friction values that are substantially different than what we’ve gotten used to thus far…
Different enough that I’ve halted development of my own RBJ-based project until 2.45 hits.

That being said, I would remind you that the minimum mass value is .01( not .1 as is sometimes assumed), and that there is a Damp value (0.0 to 1.0) that you can use to help minimize passive movement of your dynamic objects.

Keep trying and let us know if you find a solution before the next release!!!


Thank you for the reply Lefty.

This is exciting news about the Bullet update, I can’t wait to see what it brings. If the joint system is that different than what we are used to, will work done on the previous system come in to the new one properly? Because I’ve already done quite a lot of work on my project, but without inelastic joints with reasonable weight ratios, I’m not really sure it will work at all.

I’ll keep playing with weight ratios and damping settings, and I’ll definitely let you know if I can come up with anything decent. I’ve noticed quite a few people wishing for this feature.

On the other question, do you (or anyone) have any idea on how the ragdoll can control an armature so perfectly as was in that example? Once again, I don’t need it for in-game functionality, I know that’s not currently possible. But I do need a baked ragdoll rig in an animation. This is another very important part of the project.