Detaching a soft body Anchor from a moving rigid body...

[BTT1024]

Hi, I am trying to animate an object pulling a blanket across the screen where it would release the blanket midway in the timeline and the blanket would fall to the ground. In my testing - See attached .jas ZIP file, I have a soft body object with anchor points set and the "Attach to object" property set to the rigid body object. The rigid body is keyed to move across the screen - And I recorded the (soft body) Anchor key "Tag On/Off" property in the "On" state at the beginning of the timeline and then recorded the (soft body) Anchor key "Tag On/Off" property in the "Off" state at the 37th frame...

But, the soft body (blanket) does not detach from the rigid body when playing back the frames... But, I do notice if I pause/stop the play back after the keyed Anchor key "Tag On/Off" "Off" state and then click the play button again, the soft body (blanket) detaches and the rigid body keeps moving like I planned (until the end of the timeline).

Do you think this is a bug in Cheetah3D - Or am I trying to do this the wrong way ?

Any assistance would be appreciated - Thank you,
Brian

 

[frank beckmann]

Hi Brian and Welcome.
Just discussed with Martin. It´s no bug to be clear - but simply not available. When the simulation starts there´s no way to release the anchored points.
Can you describe what you want to achieve so we may find an alternatively approach?

Cheers
Frank

 

[BTT1024]

Frank,
Thank you for responding quickly... My goal was to have a character I am working on (testing with a bent cylinder), drag a soft body blanket along the ground to a certain point in the timeline and then release the blanket, letting it fall to the ground - see animated GIF below... I wanted the soft body cloth like physics of a real blanket dragging along the ground then falling (gravity) to the ground...

I've tested so many different methods to try and achieve the described animation, but found no way to do it - Other than to use duplicate objects staged, a dup character and a dup blanket (soft body) with no anchor points set, in the view but not visible (in renderer and view) until the point in the timeline where the blanket should be released and the character continues onward, for which I then record the switch OFF of the initial character and blanket's view in renderer and editor, then switch ON the dup character and dup blanket's view in renderer and editor and record the motion of the dup character onward...

Below is the animated GIF of what I achieved using the method described above - But, I am wondering if there is another way to achieve the same results (I've tried but found no other way to do it) - Do you know of another way to do this? (if not, I will stick with the method described above).

Thank you for your assistance,
Brian

 

[frank beckmann]

Okay - what seems to work quite well is to split the animation into 2 takes:
1. take 1: bake the simulation untill the frame where you want the release to take place by shortening the timeline.
2. make a new take and adjust the timeline to start at that frame where take 1 ends.
3. copy&paste the blanket into the scene (I deleted the anchor tag but think it doesn´t matter) and keyframe the bent cylinder falling down (moving along Y-axis) making it invisible for render and make a double to continue the "fly"
4. the landscape object´s rigid body tag needs to be set to concave
5. now render take 1 and take 2 and sew it together in a video app
Unfortunately soft body seems not to coming to a halt:

Cheers
Frank

 

[Helmut]

* A minor matter:
* FWIW: There seems to be no need to duplicate the tubular object.
* This refers to your original concept. Of course, a re-duplication is redundant in a split movie consisting of 2 takes.

As to the ∞ quivering soft body dynamics in C3D: There was a thread on that quite some time (> 1 year ?) ago. I (very) dimly remember experimenting with the parameters and believe I got the soft body object to become static (eventually). Unfortunately, I can neither find the associated .jas nor any notes I may have recorded then

 

[BTT1024]

Frank and Helmut, Thank you for the help...
- I did notice the quivering of the blanket after it lands on the ground - But, that's OK, I can live with that... I did a quick search on the forum and found the post titled "How to eliminate Soft body shake and shimmy?" - https://www.cheetah3d.com/forum/index.php?threads/12412/

- In that post by user "jdmac", he asks "would it be possible to deactivate a soft (and rigid) body objects upon collision with another specified soft or rigid body object?"
- But, that's not possible at this point as I've tried to record the "tag on/off" property but that doesn't turn off the dynamics effect on the object for some reason....
- The user "jdmac" referred to a post on stackoverflow.com related to the Bullet Physics engine, so it seems that's the way the physics engine works... There may be some script-able property setting that might work perhaps, but for my purposes I'm OK with the way it's working now - I've got a lot of other animation pieces to work on for my project so I will let that one go for now.

Thank you again,
Brian