On Mon, 13 Mar 2000 17:27:07 -0000, Tom Melly wrote:
>I'm suprised - I'm trying to write a short newbie tutorial on object
>transformations, and one of my general rules is always create objects with a
>known point at <0,0,0>. Don't you lose track of where you objects are going
>to end up if you scale them? (or at least find it harder).

If you create it where you want it, you don't need to scale it.  I don't see
the problem here.

Okay, to be honest, I still follow the rule of creating things at the origin.
But if I'm going to make a simple stool, I do this:

 union {
   box {<-6, 36, -6>,<6,37,6>}
   intersection {
     box {<-8,0,-8>,<8,36.5,8>}
     cylinder { <-5,0,-5>, <-4,36.5,-4>, .5 }
     cylinder { < 5,0,-5>, < 4,36.5,-4>, .5 }
     cylinder { <-5,0, 5>, <-4,36.5, 4>, .5 }
     cylinder { < 5,0, 5>, < 4,36.5, 4>, .5 }
   }
 }

That is, I create the parts of the stool where they should be, relative to the
fixed point on the stool that I have chosen to have at the origin (in this case,
a point on the floor directly under the center.)  To me, this looks a lot 
cleaner than trying to create and translate and rotate and scale all those 
components to get the desired result.  I will still translate and rotate the 
stool to put it where I want it (but I won't scale it, because it's already to 
scale.)

The exception, of course, is when I need an ellipsoid or a torus.  Those have to
be created at the origin.  (In fact, I wish there were an alternate syntax for
toruses that took a center and an axis so I could work with them without having
to wave my left hand around to figure out the rotations.)

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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