Blender v3.1.2
UE5.0 Official version

Content ： export FBX Model and Baking and exporting FBX Animation , be used for UE5 Load and render .

current MMD The skeleton of the model , Used a lot Gift bone , This is in Blender in , It is realized indirectly by the driver .
under these circumstances , stay UE It becomes very difficult to manipulate bones with donor bone relationship , But this article is not to solve this problem ...

1 export FBX Model time ,FBX The skeleton has many names with _dummy The skeleton of

Solve the problem when exporting FBX Model time .FBX The skeleton of the model will have many names _dummy The problem of strange bones .
those The name carries _dummy Strange bones , It's actually IK bone and Gift bone The drive's auxiliary bone . Used to drive By IK Bone and Donated bone The movement of .
export FBX Model time , Click The green arrow indicates Trash can icon , You can delete IK Bone and donor bone The driver of , here IK Bone and bone function Will be temporarily closed .
Export FBX Model ,FBX The skeleton will not have any _dummy bones .
When the export is complete , Click on On the left of the trash can Bone button , You can recover IK Bone and donor bone drive and function 了 .
Be careful , Export FBX Model time , You cannot export bone animation directly , Because by default , Directly imported vmd Animation is needed and IK Bone and bone function Working together . Unless you've baked the animation manually （ That's what I'll say later ） 了 .

Use UE5 Load the just exported fbx Model , Find out fbx Your skeleton doesn't have any name with dummy Strange bones , success .

2 Bake bone animation manually and export

First make sure the donor bone function is normal , If not sure , You can click on the mmd_tool Panel Bone button , He will automatically rebuild IK Bone and donor bone .
In object mode , Select the model skeleton , Find the menu item object -> Animation -> Bake animation , Open the baking menu .
Here's the picture

Bake animation panel As shown in the figure below , The start frame and end frame are filled in according to the actual number of animation frames
The frame step size is generally filled in 5 or 10 That's enough , The smaller the value. , Means the finer the baking , The more resources are consumed

Be sure to select Visual framing , at present Bake IK And donated bone drives Transformation , So as to apply IK The effect of bone and donor bone , Turn it off in the back IK Bone and donor bone The function will not have any impact on the animation at all .

Select Clear curve , It can automatically remove redundant frames

Click ok , Start baking , It takes a little longer , It depends on the machine configuration .
After baking , You can see in the action editor , One more animation clip Action fragment , This is the baked animation .

Now? , Click on mmd_tool The trash can icon next to the bone of the panel , close IK Bone and bone function .
Play animation , You'll find that , The model animation is completely normal , and close IK Bone and bone function The bone animation before is exactly the same , The animation clip does not depend on any IK bone , Advanced bone functions such as donor bone .
Okay , Now you can export FBX Model time , Then check Export Bake the animation , This ensures that FBX Animation Exactly as expected .
You will now Exported FBX Animation import UE5 , You can find exactly the same .