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Thread: Transformation Matrices for Nodes Elements?

  1. #1

    Transformation Matrices for Nodes Elements?


    I believe I have most of my animation loading code working thus far. But I am having a bit of trouble with creating the transformation matrices from each <node> of the hierarchy of <node> of type "JOINT" . Here is the hierarchy.

    Code :
          <node id="BONE_Root" name="BONE_Root" type="JOINT">
            <rotate sid="jointOrientX">1 0 0 -90.000000</rotate>
            <rotate sid="rotateY">0 1 0 -0.000027</rotate>
            <rotate sid="rotateX">1 0 0 -90.000003</rotate>
            <scale sid="scale">0.025400 0.025400 0.025400</scale>
            <node id="BONE_Transform" name="BONE_Transform" type="JOINT">
              <translate sid="translate">0.000011 -20.000000 0.000006</translate>
              <rotate sid="rotateZ">0 0 1 0.000027</rotate>
              <rotate sid="rotateY">0 1 0 4.085627</rotate>
              <rotate sid="rotateX">1 0 0 90.000009</rotate>
              <node id="BIND_Head" name="BIND_Head" type="JOINT">
                <translate sid="translate">-0.000000 -0.000011 58.740158</translate>
                <rotate sid="rotateZ">0 0 1 4.085628</rotate>
                <rotate sid="rotateX">1 0 0 0.000007</rotate>

    I have been able of retrieve all the values for each node, but for each node, I dont know how I should go about multiplying its transformation data to create the Joint's transformation matrix. Can someone please show me how?

    I Appreciate the help.

  2. #2
    Senior Member
    Join Date
    Aug 2004

    Re: Transformation Matrices for Nodes Elements?

    The COLLADA spec says that the transformation elements can be converted to (column) matrices and post-multiplied in the order they are given within each <node> to compose its local coordinate system.

    So, for example: [BONE_Root] = [jointOrientX] [rotateY] [rotateX] [scale]

  3. #3

    Re: Transformation Matrices for Nodes Elements?

    Thanks for the reply marcus.

    I am using directX on my code so I need to build a row major tranfomration matrix from these <node> element transforms ( I transpose the matrices of the inverse bind matrices to make thme row major also. ). So I take each of the <node>'s tranformations and use them to create matrices for each one. For example,

    [jointOrientX] becomes its own matrix
    [rotateY] becomes its own matrix
    and so on for each transform.

    When I have turned each transform into a matrix. I concatenate them like you posted in your example below.

    [BONE_Root] = [jointOrientX] [rotateY] [rotateX] [scale]

    However, there is something wrong in my doing here becuase I am not getting the correct results on the asset skeleton when it is loaded into my 3d game. Perhaps this has to do about the post multiplication you mentioned. I dont quite understand what this means. Can you elaborate that?


  4. #4
    Senior Member
    Join Date
    Jul 2004
    Santa Clara

    Re: Transformation Matrices for Nodes Elements?

    post-multiplying with column-major matrices produces the same result as pre-multiplying with row-major matrices

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