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How to get a bone's world position

Hello,

How to get a bone's world position from a script?

apPortrait.SetBonePosition(apOptBone, targetPos) allows us to set a bone to a world position, however there is no method such as apPortrait.GetBonePosition(apOptBone).

There is apOptBone.Position, but it returns the bone's position in anyportrait's own coordinate system, which seems to be some sort of screen position.

4 answers0 replies

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RainyRizzle

Mar 14

Hi!

As you may have guessed, objects including apOptBone have values in AnyPortrait's coordinate system.

Therefore, if you want to obtain the world position in a scene, you should use a different approach.

If you enable the "Socket" option for Mesh and Bone, a "Socket" GameObject will be created separately when baking.

Socket is a Transform that contains the World Position of the object.

First, activate the Socket option of Mesh or Bone.

( https://rainyrizzle.github.io/en/AdvancedManual/AD_Socket.html )

Then, you can use the script to find and use the Transform type Socket.

Use "GetBoneSocket" / "GetOptTransformSocket" functions.

( https://rainyrizzle.github.io/en/Script/SC_Bone.html / https://rainyrizzle.github.io/en/Script/SC_Mesh.html )

Or, you can also find and use it directly from the Scene's Hierarchy.

A Socket is a simple Transform that takes the object's actual world space position or rotation instead, so you can use it easily.

If the problem is not resolved, please leave a comment!

Thank you.

RainyRizzle

Mar 15

Replying to

Hi!

Rather than simply finding the position of the bone, the Get/Set process within continuous updates is a fairly complex issue.

This is because it is an issue related to AnyPortrait's update system as well as Bone or IK Controller.

The most important point of your question is that after the "SetBonePosition" function is called, you cannot immediately get the position of that Bone or any other Bone in the Chain related to that Bone.

And related to the issue, the question seems to be "Does SetBonePosition really have to be called continuously every frame?"

AnyPortrait updates are executed after all other possible scripts have been called.

So, even if you change the value or location of Bone, Mesh, or Control Parameter, it is not reflected immediately, but after AnyPortrait is updated.

This is for reasons similar to Unity's Animation and Physics systems.

For this reason, if you want to get the bone's position accurately, the script must be run after AnyPortrait has finished updating.

However, since the location of the bone must be specified before AnyPortrait's update is executed, you must eventually make the script run in the following order.

"SetBonePosition > [ AnyPortrait Update ] > Get Bone (Socket) Position"

Of course, it would be clear to write the "SetBonePosition" function and then immediately write the codes for "Get Position", but unfortunately this is not possible due to the characteristics of the system.

We will explain using the following example.

This is an example where IK Controller is applied.

(1) This is the Effector Bone of the IK Controller.

(2) We want to attach an external object to one Bone ("Bone 3") in the Chain. The Socket option is enabled.

We wrote an example script as above.

The script above contains “moving an external object to the location of the bone in the chain in real-time.”

(1) It has 3 member variables.

- apPortrait portrait: The target AnyPortrait character.

- Transform attachedTransform: As an external object, it is moved to the position of “Bone 3” in every frame.

- Transform _middleBoneSocket: This is a variable where the Socket of “Bone 3” in the Chain is stored.

(2) In Start, initialization is performed, the Socket of the target Bone is found, and assigned to a variable.

(3) In the Update function, press the A key on the keyboard to temporarily change the position of the effector bone.

At this time, we will pause the editor using “Debug.Break()”.

By writing a script like this, you can test whether “the positions of the bones can be accurately referenced in the frame where SetBonePosition is called.”

(4) In LateUpdate, the external object is moved to the location of “Bone 3”.

This is the part you need to “Get the position of the Bone”.

Although it is unfortunate that the code for getting the bone's location is in LateUpdate rather than Update, the code itself is not complicated, so you will be able to utilize it easily.

Note that:

If you simply want to attach an external object, just register the object as a child of Socket rather than changing the location every time in LateUpdate as shown above.

(1) Place the written script in the Scene and additionally create a new object (Cube).

(2) Assign each element to a member variable in the Script.

When you run the game, you will see the external object moving to the "Bone 3" position.

In this state, let's move the Effector Bone by pressing "A Key".

Since the editor is paused by the "Debug.Break()" function, you can check whether the Socket is properly positioned in the frame where the Effector Bone was moved.

However, if you look at the image above, you can see that the external object is in a strange position.

This means that the script that positions the external object as "Bone 3" was not executed properly.

In other words, it means that the code for "Get Position" did not work properly in the frame where "SetBonePosition" was called.

(Note: Execution order issues are random, so they may appear after the build even if they are not visible in the editor.)

This problem is caused by the “AnyPortrait update system” explained earlier.

Even if the code that retrieves the Bone's position - through Socket - is written in LateUpdate in the script, if it is executed before AnyPortrait's update, the Bone's position is not properly retrieved. ("Wrong Process")

To solve this problem, you need to specify the execution order of the script, such as "Fixed Process", to get the Bone's position after AnyPortrait's update.

In "Project Settings > Script Execution Order", set the script that references the Bone's position to be executed later than the "Default Time".

AnyPortrait's updates are called at the "Default Time", so making it run later than that will solve the problem.

Let's run the game again and press A Key.

When the editor is paused, you will see the object attached, this time to the exact location of "Bone 3".

This means that the code for "Get Position" - using Socket - was called properly.

This is the answer to the issue of the function call order that you need to know when referring to the Bone's position through a Socket.

Below is the answer to your additional question, "Why does Bone's position change back after it has been applied once?"

When you want to specify the position of a bone, it can be persistent or temporary.

For example, aiming at a target would be "a case of temporarily controlling IK."

Also, when specifying the position of a bone with a script, the target position will most likely not be fixed.

Considering the many cases in which users use SetBonePosition, we implemented the function so that it is called every frame where it is needed.

So, when that function is not called, it returns to the original animation.

(Note: You can also control IK naturally by gradually changing the Weight of SetBonePosition to "0 > 1 > 0".)

We hope our answers help you.

If you need additional help, please leave a comment again.

Although you described your IK status in detail, unfortunately, we did not fully understand your situation.

It was difficult to answer because the situation of using SetBonePosition and needing to know the bone's position at the same time was very unfamiliar to us.

If you tell us more about this situation, we will be able to give you a more accurate answer.

Thank you!