Rotate bone in Space.World coordinates

[Koroldev]

Hi guys, I have little problem.

There is a function, that rotates bone

// type script function 
public static rotateBone(bone: BABYLON.Bone, quat: BABYLON.Quaternion): void {

        var result = bone.getLocalMatrix();

        var xx = quat.x * quat.x;
        var yy = quat.y * quat.y;
        var zz = quat.z * quat.z;
        var xy = quat.x * quat.y;
        var zw = quat.z * quat.w;
        var zx = quat.z * quat.x;
        var yw = quat.y * quat.w;
        var yz = quat.y * quat.z;
        var xw = quat.x * quat.w;

        result.m[0] = 1.0 - (2.0 * (yy + zz));
        result.m[1] = 2.0 * (xy + zw);
        result.m[2] = 2.0 * (zx - yw);
        result.m[3] = 0;
        result.m[4] = 2.0 * (xy - zw);
        result.m[5] = 1.0 - (2.0 * (zz + xx));
        result.m[6] = 2.0 * (yz + xw);
        result.m[7] = 0;
        result.m[8] = 2.0 * (zx + yw);
        result.m[9] = 2.0 * (yz - xw);
        result.m[10] = 1.0 - (2.0 * (yy + xx));
        result.m[11] = 0;

        result.m[15] = 1.0;
    }

But this function rotates bone in local space, and I need rotetes bone in world space. What I should change in function?

[GameMonetize]

You can get a world space quaternion and transform it to a local space quaternion using inverse world matrix

[Koroldev]

3 hours ago, Deltakosh said:

You can get a world space quaternion and transform it to a local space quaternion using inverse world matrix

Can you explain me more clearly? Because I am confusing in quternions and matrixes.

1. How can I get world space quaternion from bone?

2. When I get world quaternion, than I should change desired angle and convert new quaternion in local quaternion?

3. How to convert world quaternion to local and apply it to bone?

Thank!

[GameMonetize]

1. bone.getWorldMatrix()

2. Matrix.Invert(bone.getWorldMatrix())

3.var finalQuat = Quaternion.FromRotationMatrix(Matrix.Invert(bone.getWorldMatrix()))

[Koroldev]

11 hours ago, Deltakosh said:

1. bone.getWorldMatrix()

2. Matrix.Invert(bone.getWorldMatrix())

3.var finalQuat = Quaternion.FromRotationMatrix(Matrix.Invert(bone.getWorldMatrix()))

Okay, I wrote code, and nothing happens

var worldMat = this.boneTorsoDown.getWorldMatrix();

worldMat = worldMat.multiply(BABYLON.Matrix.RotationX(r));

var localMat = BABYLON.Matrix.Invert(worldMat);

var quat = BABYLON.Quaternion.FromRotationMatrix(localMat);

var result = this.boneTorsoDown.getLocalMatrix();
		
var xx = quat.x * quat.x;
var yy = quat.y * quat.y;
var zz = quat.z * quat.z;
var xy = quat.x * quat.y;
var zw = quat.z * quat.w;
var zx = quat.z * quat.x;
var yw = quat.y * quat.w;
var yz = quat.y * quat.z;
var xw = quat.x * quat.w;

result.m[0] = 1.0 - (2.0 * (yy + zz));
result.m[1] = 2.0 * (xy + zw);
result.m[2] = 2.0 * (zx - yw);
result.m[3] = 0;
result.m[4] = 2.0 * (xy - zw);
result.m[5] = 1.0 - (2.0 * (zz + xx));
result.m[6] = 2.0 * (yz + xw);
result.m[7] = 0;
result.m[8] = 2.0 * (zx + yw);
result.m[9] = 2.0 * (yz - xw);
result.m[10] = 1.0 - (2.0 * (yy + xx));
result.m[11] = 0;

result.m[15] = 1.0;

 

[adam]

The only way I was able to get the WorldMatrix for a bone was by using the Mesh worldMatrix and the absoluteTransform of the bone.

Take a look at the SkeletonViewer:

https://github.com/BabylonJS/Babylon.js/blob/master/src/Debug/babylon.skeletonViewer.ts#L40

[GameMonetize]

Yes Adam is correct. bone.getWorldMatrix is not enough as the bone matrix is applied to mesh world matrix