[Date Prev] [Date Next] [Thread Prev] [Thread Next] Date Index Thread Index Search archive:
Date:Mon Nov 19 11:51:00 2000 
Subject:Re: RE: RCLIB (another extension) (Correction) 
From:Aaron Sloman See text for reply address 
Volume-ID:1001119.01 

[To reply replace "Aaron.Sloman.XX" with "A.Sloman"]

I wrote yesterday:

> ...
> rc_transform_lines(
>     coords1, coords2, steps, colour,
>         widthOrShape, mode, delay, trail, proc);

> ...

> proc is one of the procedures
>     rc_draw_lines           -- for open polygons
>     rc_draw_lines_closed    -- for closed polygons
>     rc_draw_lines_filled    -- for filled polygons
> ...

> ...

> Linear interpolation of points is not ideal, since it will not
> deal with things like rotating fixed-length lines

I now realise that this comment was wrong.

Instead of using one of the three procedures listed as the final
argument for rc_transform_lines

    rc_draw_lines, rc_draw_lines_closed, rc_draw_lines_filled

it is possible to give rc_transform_lines a procedure that treats
four of the numbers as representing a rotatating line, e.g. the
first two are the location of the centre, the second the length
and the third the orientation. Then the length could be kept
constant while the other three change, producing a moving
and rotating line of fixed length.

I have added an example of this sort to the test examples at the top
of the file rclib/auto/rc_transform_lines.p, and also fixed a bug in
rc_transform_lines which stopped it working properly in some cases
if the first argument is a vector instead of a list.

Aaron
===
Aaron Sloman, ( http://www.cs.bham.ac.uk/~axs/ )
School of Computer Science, The University of Birmingham, B15 2TT, UK
EMAIL A.Sloman AT cs.bham.ac.uk   (ReadATas@please !)
PAPERS: http://www.cs.bham.ac.uk/research/cogaff/
FREE TOOLS: http://www.cs.bham.ac.uk/research/poplog/freepoplog.html