Path: utzoo!attcan!uunet!mcsun!cernvax!rmal
From: rmal@cernvax.UUCP (richard lucock)
Newsgroups: comp.sys.amiga.tech
Subject: Problems with clipping
Message-ID: <1959@cernvax.UUCP>
Date: 11 Jun 90 12:37:55 GMT
Organization: CERN, European Laboratory for Particle Physics
Lines: 26
References:

I have a program to draw a set of vectors to a window, with an option
to zoom in towards the origin. The vectors are scaled so that at x1.0
magnification, they just fit into the window.  When zooming, I don't
bother to clip the vectors myself, since this should be done by the amiga
routines.  For the first few 'zoom steps', I have no problems.  However, I
find that when the vectors get very long (eg coordinates of +/-20000)
funny things happen - the lines are draw outside the window area, wrap
around the screen (off at the top, on again at the bottom) etc.

I have checked that the coordinate *are* still within the range of the
variable types required by the drawing routines.

The data I am using at the moment is such that the *start* point of all
vectors *is* in the window area, at all times, for all zoom factors.

I have tried this both with the Move()/Draw() routines, and with the
DrawBorder() routine to draw IntuiBorder structures. I get the same
problem in both cases.

Since I am drawing to a window, via its RastPort, and windows use the layers
library, I would have thought that nothing should appear outside the
window area. Is this a known problem ? Is there some work around for it
(other than doing my own clipping) ?

Thanks,
	Richard