[Newbies] PolygonMorph intersection

Jerome Peace peace_the_dreamer at yahoo.com
Thu May 3 22:55:17 UTC 2007

PolygonMorph intersection

Hi Sudheendra Hangal,

You can work with the morphs shadows.

First pass, check if the boundries intersect. If they
don't then your done.

Else get a form the size of the boundry intersection.
In it draw the shadows of each morph s.t. only the
double shadow shows. Then check to see if the form is
all white. If it is not then the morphs intersect.
Obviously if one morph is a rectangle you just have to
see if the others shadow falls on the boundry.

To track down how to do this in a workspace type 

select it and type Cmd-m (for implementers) This will
give you a browser with all the definitions of the
method in the system.

You might be interested in looking at the code I wrote
for puzzleboards:

The index to that and other pieces of code are at:
Goodies from Jerome Peace

The site is bob's superswiki.

I haven't look at that code recently so let me know if
it works or if you have problems. I am pretty sure the
project won't be loadable. Too much has changed and
projects are very sensitive.  The changeset is what I
think I was claiming would work in 3.8 and 3.9.

Let me know how you get on.

Yours in curiosity and service, --Jerome Peace

>  Thanks, Jerome - have filed the issue in Mantis.
>  I'm looking for the easiest way to figure out if
>  polygon A is contained
>  inside polygon B.
>  One way to do this is by checking if polygon A
>  intersects any segments of B
>  and any one of A's vertices lies inside B.
>  is there a better way ?
>  Thanks,
>  -sgh

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