>
> The order in which transformations appear in the VRML file must be
> respected.
>
> To stay with the example by Patrick Sweeney <pjs@clark.net>:
>
> Translation { translation ... }
> Rotation { rotation ... }
> SomeObject
>
> When you think of local coordinate systems (what modellers usually
> do), you first translate SomeObject to its place and rotate it then
> locally on that place.
>
> To achieve this effect in mathematical terms you must reverse
> transformations. I.e. you have first to rotate SomeObject at the
> origin and then tranlate it to its position. If you did the
> Translation first you would rotate the object along a circle around
> the origin going through that object.
>
> In my eyes, this is no special Inventor issue, just basics of Computer
> Graphics Transformations.
My point of confusion was not with how to perform transformations, but
that from the VRML spec it is not clear which order to perform the
transforms in. My original assumption was that I am building up a
transform matrix that first translates and then rotates (which is
backwards to the way it is supposed to be done), and that this matrix is
then applied to any nodes following it. This, as Stephen pointed
out, is part of the problem. The VRML spec assumes intimate knowledge of
Open Inventor.
> > bye, > Michael >
Later.
- pat