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Baked Animations with 1 Frame Delay using Constraints
Open, Needs Triage by DeveloperPublic


System Information
Operating system: Windows 10
Graphics card: RTX 2080 TI

Blender Version
Broken: 2.8
Worked: 2.79

Short description of error

Problem with the bake animation output with two bone constraints being child of each other, but one not influencing the other, but still doing a weird woob, delay the animation by 1 frame.

Exact steps for others to reproduce the error

I had some problems with animation in 2.79 that I fixed, but it came back in 2.8 and I can’t find how to solve it. Let me explain more about it.

The concept is simple: I have a Character that I’m animating in first person and he hold a two handed sword with both hands (he have 2 human arms). I simply put the Sword attached to a bone called Weapon_R, and the Left Hand Controller (I’m Using IK to make the hand follows two separated bones, one for the right and other for the left), using a Hand Controller to each hand. Sometimes the Armature needs to hold the weapon with the Right Hand at the botton and the Left Hand at the top, He changes the guard with each hand.

So I made a Constraint to both Arm Controllers to one follow each other, activating it or not in the timeline when I need the character to switch between hands. This worked very well in the beggining, but later I discovered that doest not work well. I noticed that when I export to a Game Engine, like Unreal or Unity, and Bake the Animation in Blender, The hand that follows the other in the animation seems to have a 1 frame delay. That’s strange. Even If I Keyframe the Influence to Zero inside the animation, It doesn’t work.

Here’s the file:

The problem was solved In 2.79 when I mark 2 checkboxes called Extra Object Update and Extra Data Update in the Relations Extras, Worked very well and the problem vanished, but they were removed and the Relations Extras drop menu also.

So, while I was creating this post I managed to avoid this problem by removing the constraint entirely from one of the hand controllers and created 2 files. One with the Left animations and other with the Right Animations, but It’s still a bug, I guess? Even clicking in the visibility Icon setting it to off and removing the Influence Keyframes the delay still there.

The bake and the export is working like a charm after that.

Here’s another video of me avoiding the problem: