Hydraulics in animation problem [Solved]

Hi, I’m new to these forums so Hello to all forum members!

I wanted to learn about animation in Blender so i made a simple test scene with a mechanic leg and wanted to rig it for an animation. At first everything works correctly, hydraulics are in place and with good rotation while posing. The problem is when I play the animation the hydraulics bones (also tried applying tracking on the hydraulic parts with the same result) don’t rotate fast enough, which results in a messed up animation…
Here’s a sample screenshot:


The odd thing about the animation is that when I reset the view somehow (for example switch to some other layer and get back to the correct layer) everything is OK:


Well, I could render frame by frame and then make an animation out of rendered images but im sure this can be solved properly…
I tried tweaking iterations and tolerace on the IK solver (track) constraint, but it changed nothing :frowning:

Here’s a quicktime animation i’ve made:

And the .blend file:

Thanks in advance for any help.

UPDATE: solved

This seems odd. Could you post the .blend file?

sure LINK, but be aware that objects are named in polish, hope that’s not a problem.

Thanks for the reply… thought noone’s interested in helping me :frowning:

hmmm is it impossible to make it better ? 86 views and still no suggestions :frowning:

You put your animation on the Armature Object which jinxed everything. When you do a walkcycle you will animate only the Bones of (let’s say) the arms and the legs going back and forth, the pelvis and shoulders twisting and the backbone springing. So now the character is walking on air in one place. Only then do you put the Armature Object (in Object Mode) onto a Path so that he can go forward at the same speed as his feet.

In this file I changed the forward movement by using the Root Bone (gora) and getting rid of the IPO’s on the Object. (usually the Root Bone will be the first bone you add and either in the spine or seperate from the skeleton and you will use it to turn left and right or bend forward, jump etc).



Thx for checking the .blend file and updating it, but the problem remains :confused: You’ve added more frames which made it a bit better (less noticeable), but i don’t want to add frames just for a slight change… If you play it a bit faster (for example by manually moving the timeline slider) you get the same result as before. My aim is to get the mechanics still so even the fastest moves are handled correctly.
As for the root bone, I’ll remember that :slight_smile: don’t know why i haven’t done it that way in the first place… it looks even easier than rotating and positioning all the meshes :slight_smile:

Yes I see now. Unfortunately this is a known bug:



Try the file I uploaded.
I think the problem is you are using “IK” as the constraint, where “track to” would be the better option. Also, I found that there were discrepancies at some positions even when track to is used, if the object being tracked is an empty, so I duplicated some bones and used those as targets. The empties could be deleted without affecting the animation now, I think.
About the discrepancies. Have anyone else noticed them? For example, in the above blend, if you replaced the _tgt bones with the empties in the track to constraint, (even after adjusting the xyz orientations, so that it tracks properly). the tracking is slightly off when the foot is nearly straight. Perhaps some error is being introduced when multiple level of tracking is involved? (empty tracks bones, bones track empty in turn) where positions are being translated from bone space to object space then back to bone space again? I’m not really sure if this is correct, but that is how I would think of it…(tracking not accurate with empties but accurate with bones as targets)

Yes, in the link to ook’s thread in my post above yours.


:smiley: :o
You’re absolutely right. I was just too eager to post my message without reading previous replies first. So it is a known bug. Hope they manage to fix that in the next release version. Well, it was a good exercise in getting to know what works and what doesn’t. :slight_smile:

Hi, kroni. I’ve solved your problem.
I replaced all empties that determined the posisions of pistons and cylinders with bones.
Try the file I uploaded below.


sorry for the late response.
that seems to do the trick… thx for help