Re: LANG: VRML Transforms (fwd)

Stephen Chenney ([email protected])
Fri, 6 Oct 1995 12:18:15 -0700 (PDT)

> > The other thing missing from the spec is which way a matrix node is
> > applied. Is it multiplied on the left or on the right? Hence, does the
> > translation part go on the bottom row or the right column? The spec says
> > nothing about this, forcing people to waste their time finding out. And
> > don't tell me that "everyone does it that way" because not everybody does,
> > and even if they did it is no excuse for omiting it.
>
> Huh? The choice of column vectors vs row vectors is totally arbitrary.
> If you use column vectors then the translation is in the right column and
> you postmultiply to accumulate transformations. But this has no bearing
> on the VRML format. It's an implementation issue and there's no right or
> wrong way.

Yeh. I agree with that. But if you are supplying matrices to someone else's
implementation then you need to know how what format to use. That's the VRML
case.

> How an SFMatrix is written to a VRML file is important, but the spec seems
> pretty clear on this.

Here I will admit inadequate esading of the spec. I did not know that the
SFmatrix description contained information about the ordering. My mistake
(in a big way ;-).

Steve.

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