Welded parts acting as if they're anchored

Bug Reports Studio Bugs
#1

Issue:
Welded parts will act as if they’re anchored until a 3rd party influence (Ie: Part touches it, studio drags the object etc.), then it acts fine. They also will not interact with other objects at all (Ie: Attach a brick to one of the welded parts, and it won’t respect the new position until it’s touched.)

Video of issue: http://gyazo.com/880fe802849b5a0d3021c25c1e71478e

Repro steps:

  1. Have two welded parts (Weld doesn’t matter)
  2. Adjust C0/C1 on part so it’s different from the original.
  3. Notice how the parts will act as if they’re anchored in mid-air, and won’t respect joints.

Edit: I should mention that both cubes are completely smooth, and they are not attached to the baseplate in any way at all.

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#2

Which one of these parts is Part0?

#3

One on top

#4

I should clarify, it doesn’t matter where the weld exists, or which part is the part0/1, it does it regardless.

#5

Can confirm, here’s what seems to be a solid repro

https://www.dropbox.com/s/m70iso0243qphkl/weld%20weirdness%20repro.rbxl

Click reset model to create the model, move weld to move the weld and see the bug. If you move the weld while the parts are still wiggling around it will fall as expected, but if you move the weld after they’ve settled something needs to touch them before they’ll move.

#6

This isnt even any new bug, its been there for years probably.

Basically roblox seems to assume that weld properties are not changed during the lifetime of the weld, and as such changing the properties does not update them graphics while the body is in the sleeping physics state.

There is another possibly related bug which might have been fixed, where if you have a moving object, and then weld it to an anchored object, the previously moving object magically appears in some random position it was in the past before you welded it.

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