Math question: How to compute the area of polygons
Dar Scott
dsc at swcp.com
Wed Mar 19 12:43:01 EST 2003
On Wednesday, March 19, 2003, at 09:05 AM, Geoff Canyon wrote:
> But before you even do that, you should come up with a rough, simple
> calculation that will tell you there is no collision, or that you need
> to do the more exact test. So for example, if polygon A has no point
> more than 30 pixels away from its loc, and polygon B has no point more
> than 25 pixels away from its loc, then your first calculation would be
> the distance between the loc of A and the loc of B; if it's more than
> 55 pixels, there is no intersection. If it's less, then you do the
> more exact calculation.
A rough test is a very good idea, especially if there are lots of
objects that might collide.
An alternate rough test is the bounding rectangle overlap.
> If you're looking for collision detection, I think it would be faster
> to check the line segments of polygon A against the line segments of
> polygon B to see if any of them intersect. If they do, there's a
> collision. There may be a faster way than that, but I think at least
> that it would be faster than computing the areas.
Ah, I just mailed off the same idea. There is a hole. That is the
case of one being completely inside the other. I covered that in my
mailing, but it may not be needed.
Dar Scott
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