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I'm trying to make a systematic way of pickup up and dropping objects in blender (2.8, so no dynamic parent addon).

What I've done so far is to add a child of constraint to the object being pickup up, set the parent to a specific bone, then pick up it and move it around with keframing the influence etc... then when I try to DROP it the issue comes.

WHat I've been doing is, once keyframing the influence back to zero and seeing the object reset to its original position, just manually repositioning and rerotating it to approximately the same position as last frame... But as you can gueess, that is pretty ridiculous to do, there should be a way to copy the position it was at on the last frame.

I was looking on here and I found someone said to say to keyframe the visual location/rotation the frame right before setting the child of influence to 0 and then duplicate it to the next frame, but when I simply add any "visual" keyframe (while the child-of constraint is still on), it moves the position to some completely different place ?()?

Anyone can easily duplicate this by making an armature, then adding a child-of constraint to another object etc... and when you get the influence to 1, just try adding a visual keyframe.

Why does it mess it up, and how can I fix this / drop an object easier (WITHOUT dynamic parent addon since it doesnt work in 2.80)

B''H Bi'ezras -- Boruch Hashem
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  • This is how I get around this problem... https://blender.stackexchange.com/questions/87906/robot-arm-move-a-box/87929#87929 – Edgel3D Jan 01 '19 at 00:57
  • @Edgel3D wow cool I Didn't know you can keyframe the visibility! In fact, I'm trying to do so now (in blender 2.8), and its giving me an error that no suitable context is found... what keyframe options should I use>? – B''H Bi'ezras -- Boruch Hashem Jan 03 '19 at 23:00
  • To switch between objects, take the timeline cursor to frame 1. Place the mouse onto the eye icon in the Outliner and press 'i' to "Insert" a keyframe for frame 1. This will ensure the object is visible at the start. If it's to be invisible, left click on the eye, then press 'i'.

    Later, at the frame where it's to disappear/reappear, click on the eye and press i again.

    Keyframes for each switch will appear in the Dopesheet.

     – Edgel3D Jan 03 '19 at 23:44
  • @Edgel3D except that when I press "i" hovering over the "eye", "I" get an error – B''H Bi'ezras -- Boruch Hashem Jan 04 '19 at 00:26
  • Do you want the Blend file that did that pick-up and drop off? I did that with Vers 2.77a I think and not sure 2.8 will run it. The eye switching should be basic enough and not too version dependant, surely? It was rendered in OpenGL. – Edgel3D Jan 04 '19 at 23:55
  • @Edgel3D I guess it can't hurt, but maybe try just keyframing the eye in 2.8 to see if it works for you, and what keyframe defaults are needed – B''H Bi'ezras -- Boruch Hashem Jan 06 '19 at 06:46
  • @Yaakov5777 I don't have 2.8. All my work is done on 2.77a. You've probably tried this, but if you start off with the default cube and try switching off it's eye icon in the Outliner and keyframe that, it should be conclusive enough. Perhaps it's a bug? As I understand it, 2.8 is still in the Beta stage. – Edgel3D Jan 07 '19 at 00:06
  • @Yaakov5777 how did you get on? An alternative to visual switching would be to physically swap them over. Take the unwanted one somewhere else. I tried another method that doesn't need switching. Just reverse the parenting so the monkey's horizontal travel will move the claw. This allows the claw to move up and down without affecting the monkey. When the monkey/claw parentage is to be broken cleanly though, it all comes down to using a switched duplicate. The influence slider in the 'Child of' modifier doesn't fully achieve this. – Edgel3D Jan 12 '19 at 01:11

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This is the best method I've found pick up and drop and object using the aforementioned child of constraint with an additional copy location and copy rotation constraint on that same object. Then animating the influence siders of the copy location and copy rotation constraint to achieve the desired effect. There is no need to animate the child of influence slider using this method - you can keep the child of influence slider to full strength: 1.000. enter image description here

Dustin Young
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