Hi
I guess this is more of a wish than a question, but I'm consistently
and pleasantly surprised by your answers :-)

What I'd like is to be able to apply arbitrary transformations to
vector expressions and get vector expressions back.

The problem is, with something like an articulated robot arm, I want to
have pneumatic cylinders that run from one joint to another, where the
other joint has had an arbitrary transform{} applied. If I could apply
the same transform{} to a vector identifying the point on the un-transformed
object I could use that as the target for the other end of the cylinder.

-------

<Wish>
On a closely related note, is anyone familiar with constraint
resolution systems, like the one implemented in Metafont?
And has anyone thought of adding such a constraint
resolution system to POV-Ray?

In Metafont you can say things like

        transform T;    % declare T as an unknown transformation
        % z1 z2 etc are known points (vectors)
        z1 transformed T = z2;
        z3 transformed T = z4;
        z5 transformed T = z6;

and after enough such constraints have been specified, T can be
used to transform other points. (Metafont only has 2 dimensions
to worry about of course).

The really cool thing about Metafont is that its variables are
variables in the mathematical sense: they take on a value only
when enough is known about them, so it's quite alright to say

        z1 = 1/2[z2, z3];       % z1 is half way between z2 and z3
        z2 = (1, 1);
        z3 = (3, 5);

Where none of the variables previously had values, and after which
z1 magically has the value (2, 3).
</Wish>

Well, I can dream :-)

-- 
Bill Hails

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