BABYLON.Bone.prototype.setAbsolutePosition

[Samuel Girardin]

Hi, 

 

I add for some tests  BABYLON.Bone.prototype.getAbsolutePosition , this was easy returning m12,m13,m14 of the bone's _worldTransform matrix. Now,  I try to add setAbsolutePosition method to bone, and I failed. Certainly due to my bad matrix knowledge, I tried to get some inspiration from Gwenael push about Mesh..setAbsolutePosition. With no succes. 

 

If someone got an idea to achieve that (Gwenael ?!) , it would be super cool !

 

Sam.

[Samuel Girardin]

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[Samuel Girardin]

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[gwenael]

Hi Samuel,

 

Really sorry but I have been so busy recently by a project at work that I haven't spent time on this forum. I haven't played so far with bones in BabylonJS but I might be able to look at it. Could you share what you have done so far?

[Samuel Girardin]

Hi gwenael ! 

 

So about skeleton and bones : I really want to be able to move one bone, or a group of bones to an absolute position. I  understand the recursivity of Bone.prototype.getAbsoluteMatrix. I thought if I did something like the inverse of this method, By first translate the root bone and apply this transformations to all other bones, I would be able get THE bone MATRIX I want for moving my bone to his expected place. I failed, I try during several days.

If you want to have a look here is a link : http://www.visualiser.fr/Babylon/Skin/Default.htm

 

Here is some screen capture with explanations... I would like to be able a bone or or group of bone where I want. I understand, when the skeleton is animated, I have to apply thoses transformations after the skeleton is updated. If you have one solution or some new ways I didn't explored... Thks. Sam.

 

[AndyBeaulieu]

I am trying to do the something very similar...

 

Given the position and rotation of a mesh in the world, I want to position a bone in the same position and orientation.

 

Does anyone have any ideas on this?

 

Thanks!

[GameMonetize]

Bones have a function called updateMatrix which update the associated matrix.

 

The final matrix (absolutematrix) transmitted to shaders is built using this matrix and the bone's parent absolutematrix:

BABYLON.Bone.prototype.getAbsoluteMatrix = function () {

        var matrix = this._matrix.clone();

        var parent = this._parent;

 

        while (parent) {

            matrix = matrix.multiply(parent.getLocalMatrix());

            parent = parent.getParent();

        }

 

        return matrix;

    };

[AndyBeaulieu]

Thanks!!

 

I'm still not getting it though. It seems like no matter what I send to bone.updateMatrix(), the deformation does not update on the mesh.

 

It's like my changes are lost in the call to _updateDifferenceMatrix(), but I don't see how.

 

I will try to make a demo of the issue, but any thoughts are welcome!

[AndyBeaulieu]

Here is a very small test project to show what I am trying to do...

 

http://www.andybeaulieu.com/downloads/BoneSetAbsolutePosition_022214.zip

 

The project has (1) a mesh with skeleton, and (2) a box that is nearby and slightly rotated, like so:

 

 

 

 

 

What I am trying to have happen is that the "head" bone gets positioned and rotated in the same world space as the box, like so:

 

 

I have a stub started, but nothing else because everything I have tried has failed

 

So if anyone can help with a function implementation like that below, which would accept a bone and a mesh, and then move that bone to the mesh and rotate, many thanks in advance!

    THEGAME.Engine.prototype.moveBoneToMesh = function (bone, mesh) {               // ********************        // need some help here...        // this function should set "bone" position and orientation to         // be equal to "mesh"        // ********************        var matrix = mesh.getWorldMatrix().clone();                     // also, calling updateMatrix here seems to do nothing, regardless        // of what matrix value is sent in?        bone.updateMatrix(matrix);          }

[Samuel Girardin]

Hey Andy  (it starts like a french song !)

 

I think we try to achieve the same thing. I work on other stuff for now... Perhaps I don't understand your problem, but it seems you don t manage to see any mesh displacement or transformation.

 

In my case I manage to displace  (the hand of my 3D mesh). Not at the right place ... For that, if  I don't call something like  : 

this.scene.beginAnimation(this.meshSkeleton , 0,1,true, 1); 

I can't have the transformation when I use 

this.meshSkeleton.bones[index].updateMatrix(matrix)

I'm almost sure calling the skeleton animation just from one frame tell to the engine to update all the skeleton. Without that I can't see any tranformation(there must be an other way to update the skeleton)

My problem is to compute the right matrix ...  Perhaps this can help. I'm a bit lost on this..

 

Sam

      

[AndyBeaulieu]

Hi Samuel,

 

Adding in a call to beginAnimation _did_ succeed in applying the deformation to my mesh, thanks!

 

But I have the same outstanding issue as yourself now - I am not sure how to compute the correct matrix either.

[Samuel Girardin]

Andy, could you try that ?

 

I'm not sure to have -the- solution, but it sounds good.. I use dude.babylon if you want to test my code.

 

Edit : Transformation are relative to the box position.

// the dummy box with 2 rotations tricks to well orient the headthis.dummyHelper.rotation.y =- Math.PI / 2;this.dummyHelper.rotation.z = Math.PI / 2;var matrix:BABYLON.Matrix = this.dummyHelper.getWorldMatrix().clone();    matrix.invert();// in this case index=7 is the bone head root , if you want to try with the hand the index = 34this.meshSkeleton.bones[7].updateMatrix(this.meshSkeleton.bones[7].getAbsoluteMatrix().clone().multiply(matrix));

[AndyBeaulieu]

Thanks for trying and sharing!

 

Unfortunately it is not working with my mesh. If I send in the topmost parent bone ("hip"), then it works, but any other child I try does a bad scale, rotate and transform on the mesh.

 

Maybe it is something specific with my mesh - I haven't tried it with "dude" yet.

 

I'll keep playing with it - it must be a hierarchical issue - if I start with the hip bone and then work through the children, maybe it can be fixed.

[AndyBeaulieu]

Just pinging this one again, does anyone have any further ideas on this? 

 

Basically, I need to set world position and rotation of a bone inside a skeleton to have the same rotation and position as a mesh in the world. I am not understanding the bone's matrix and parent relationship enough to pull this off.

 

More details here -

 

http://www.html5gamedevs.com/topic/3736-babylonboneprototypesetabsoluteposition/?p=25777

[GameMonetize]

Starting from :

this.meshSkeleton.bones[7].getAbsoluteMatrix().clone().multiply(matrix)

 

I think it is just a matter of getting the inverse of the absoluteMatrix to block parent hierarchy

[AndyBeaulieu]

Do you mean the inverse of the parent's absoluteMatrix?

 

Something like the following? Although this doesn't seem to quite work...

THEGAME.Engine.prototype.moveBoneToMesh = function (bone, mesh) {        var meshMatrix = mesh.getWorldMatrix().clone();        meshMatrix.invert();        var boneMatrix = bone.getAbsoluteMatrix().clone();        boneMatrix = boneMatrix.multiply(meshMatrix);        if (bone._parent) {            var parentMatrix = bone._parent.getAbsoluteMatrix().clone();            parentMatrix.invert();            boneMatrix = boneMatrix.multiply(parentMatrix);        }        bone.updateMatrix(boneMatrix);        that._scene.beginAnimation(bone._skeleton, 0, 1, true, 1);    }

[GameMonetize]

Could you prepare me a small sample somewhere ? (jsfiddle is great)

 

I promise to find what you need

[AndyBeaulieu]

Okay, here is a jsfiddle - 

 

http://jsfiddle.net/andybeaulieu/9Ffv5/37/

 

If you go there and:

 

• click the "Copy Bones" button. This creates a series of box meshes that mirror the skeleton of the guy in the scene.
   
• click the "Move to Bones" button. What _should_ happen is that the bones in the skeleton move over to their respective meshes in the "copy" of the skeleton to the left. So they should translate, rotate (no need to scale) to the box meshes in the skeleton to the left.
   
• looking at my code, the problem function is right at the top - moveSkeletonToBones. In there, I want to iterate through each bone in the skeleton, and orient it (translate and rotate) to its respective "copy" of the bone to the left.

Thanks for any ideas. I think this would be a powerful function for rag dolls and programmatic animation of the skeleton!

[AndyBeaulieu]

*bump* ?

[GameMonetize]

I'm on it

[GameMonetize]

I have a question: why are you not just moving the dude where the bones are ?

[GameMonetize]

Like this:

http://jsfiddle.net/9Ffv5/40/

[AndyBeaulieu]

heh, that would be easy wouldn't it

 

But my what my ultimate goal here is to create a ragdoll. So, the box meshes to the left will eventually have physics added to them and joints created between them.

 

Then, by matching the position and rotation of the box meshes to the bones in the skeleton, I should have a ragdoll... That's the idea anyway I am open to other suggestions though.

[Samuel Girardin]

Hey Andy,

 

Just for illustrated, I think you want to  achieve something like that (stage3D demo (rip)). Shoot the ragoll.

 

I'm right ?

[AndyBeaulieu]

Yes Samuel - exactly!

 

Nice demo by the way