[GRASS5] Q. How do you find the islands for a given area?
Eric G. Miller
egm2 at jps.net
Sat Feb 24 17:30:20 EST 2001
I've been looking into the d.area island drawing problem. Anyway, I'm
trying to figure out how you find out:
For a given area A:
How many interior boundary islands does it have?
How do I get line_pnts struct(s) for just these interior islands?
I've discovered I can get the total number of islands in the map with
And, I can get an island using:
Vect_get_isle_points (&Map, isle_num, &pnts)
Problem is, I want to know just the islands for the current area. Even
with V2_get_area (&Map, area_num, &area_ptr), the area_ptr->n_isles
gives me nothing (even though I'm using a little test vector that has
two areas each with one interior island).
My idea for a solution to the filled area drawing routines would
basically connect all the islands to their outer area where the
island is closest to the area boundary. (Make any sense). I don't know
how else these holes could be handled.
| _ |<= Area
| / \ |
| \_/ |
| Isle^ |
| | | (Area "line points" now loops down and around island,
| / \ | then back up to where it dropped down to the island
| \_/ | to continue the rest of the area boundary)
What am I missing?
Eric G. Miller <egm2 at jps.net>
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