Well, dependant on how accurate you want it, you
could try this:
declare a small sphere, positioned exactly like the
"fingertip" of the robotarm. Then, do the same
transformations with it.

In effect, this should position the declared sphere
exactly at the same tip as the arm where you want
the particles to come from.
Now, you use min_extent and max_extent to get
the boundary box of the sphere, and since the sphere
is completely round, you should get a box with
equal sides. Calculate the center of the boundary
box ( done like this: (min+max)/2 ) and use that as
position where particle enter the world.

This more or less tracks the arm, instead of you
doing all the calculations.

Aside of that, you're way is probably the only other
possiblity out there, as far as I can tell.

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights

> Perhaps this isn't the place to be asking this - though it is related to
the
> post.
>
> I've got my (at the moment fairly basic) particle system up and running
and
> I'd like to generate particles at the end of the arm. However, the arm
> movement at the moment is forward kinematics - i.e. the general structure
is
>
> #macro ArmPart2(angle 2, angle3...)
> // Modelling here
> object (ArmPart3(angle3...) rotate y*angle2 translate <5,4,-20>)
> #end
>
> #macro Robot(angle1, angle 2, angle3...)
> // Modelling here
> object (ArmPart1(angle2, angle3...) rotate x*angle1 translate <0,35,2>)
> #end
>
> with similar definitions for ArmPart2, ArmPart3 etc, and the robot being
> placed by a single call to Robot(...). The position in global coordinates
of
> the end of the arm doesn't seem to be very easy to get at. At the moment,
> I'm finding the position with a long formula with lots of embedded
> vrotate(...) functions, but this hardly seems the most elegant solution.
>
> The way I would usually place things at the exact end of the arm is to
place
> them in the macro that defines the very end part of the arm. However, this
> isn't possible in this case, as the particles have to move realistically
> relative to the global coordinate system, not relative to the end part of
> the arm.
>
> Anyone got any suggestions as to a better way than a very long equation?
>
> Regards,
>
> -Chris
>
>


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