Re: [boost] Re: A preliminary proposal: AGG project

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-05-05 20:37:36

At 01:55 PM 5/4/2002, Maxim Shemanarev wrote:

 >...
 >
 >Suppose you're working on a GIS system. Here scaling is essntial and very
 >important. And although AGG renderers have low-level clipping, it can 
fail
 >when you try to enlarge your map because of integer overflow. Besides 
it'll
 >take much more time and memory if you render privitives whose coordinates
 >are far outside of the rendering framework. What is the solution? Very
 >simple - you just include a clipping converter in the proper place of 
your
 >pipeline. This converter clips *polygons* (it's going to be implemented 
in
 >AGG soon). On the other hand, there's a number of applications where this
 >high-level clipping can be omited.

I ran into the clipping problem you describe some years ago. Because the 
graphics package didn't handle the integer overflow issues, we hand to 
pre-clip all inputs, which was a major pain in the whatever.  A pipeline 
approach sounds very useful.

For a lot of digital geography applications, there is a serious issue of 
who, when, where, and what has the responsibility for conversion from world 
to device coordinates.  Can coordinate conversions likewise be done at the 
point in the pipeline that makes the most sense for the application?

--Beman