Re: guppi coor system

[linas linas org]

It's been rumoured that Rob Browning said:
> > you compose matrices to get the desired combo.  Then, a point in
> > 'modeling coords' is (x,y,z,1) and the point in device coords is
> > just M * (x,y,z,1) (well, technically, for true 3d, to get
> > perspective effects, you need to divide by z at this point, and you
> > had to set up a funny matrix for get the perspective to work, but
> > we're not doing 3d right? :-) )
> 
> And even if we were, most of it's not that hard, and as you point out,
> using homogeneous coordinates (as you've suggested) makes it so that
> you can represent any composition of operations as a single composite
> matrix which represents a fixed computational cost, per-pixel.

Ack! NOOOOOO!

There is some fundamental miscommunication here.  This is *not* per
pixel!  We don't want anything per pixel!  

Coordinate systems is a concept one uses just to specify the endpoints
of a line, the radius & center of a circle, etc.  There's nothing in
here having to do with pixels! 

-------