Transform Node's "center" field 
Author Message
 Transform Node's "center" field


> ...
> it, and then modifying the translation, and center field parameters.  However
> I still do not understand how the center field works.

The center field specifies the center of rotation. It has no effect on position
(since that is what the translation field is for). If you are conversant with
matrix formulations of transforms, this is taken directly from Carey&Bell
( http://www.*-*-*.com/ #Transform):

Given a 3-dimensional point P and Transform node, P is transformed into point P'
in its parent's
coordinate system by a series of intermediate transformations. In matrix
transformation notation, where C
(center), SR (scaleOrientation), T (translation), R (rotation), and S (scale)
are the equivalent
transformation matrices,

    P' = T C R SR S -SR -C P

The following Transform node:

Transform {
    center           C
    rotation         R
    scale            S
    scaleOrientation SR
    translation      T
    children         [...]


is equivalent to the nested sequence of:

Transform {
  translation T
  children Transform {
    translation C
    children Transform {
      rotation R
      children Transform {
        rotation SR
        children Transform {
          scale S
          children Transform {
            rotation -SR
            children Transform {
              translation -C
              children [...]


Chris Morley

Sun, 10 Jun 2001 03:00:00 GMT  
 [ 2 post ] 

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