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 2D Polygon's and waypoints  (Read 2089 times) 0 Members and 1 Guest are viewing this topic.
Lemon

Senior Newbie

Java games rock!

 « Posted 2005-09-23 08:19:00 »

Hey

I have a problem with a current project I'm working on and I havn't been able to come up with a decent solution for quite some time now

The problem is this:

I have a Polygon object in two dimensions and I wish to find the Waypoint objects for this Polygon object.  The  waypoints are positioned such that if each waypoints was connected to its neighbor they should form a new Polygon whose lines are parallel to the original Polygon and are 10 units away.

i have tried finding the centre and extending a line from the centre through each point of the polygon but this does not work for Polygons which are convex or have an irregular shape. Surely there is an easy solution to this problem  . Efficiency is not terribly important as the waypoint positions are precalculated in my application.

Simon

Riven
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 « Reply #1 - Posted 2005-09-23 09:20:46 »

Don't use a center-point, that requires all polygon-points to be at the same distance fomr the center, which is rarely the case.

Calculate the 2D normal of each edge, go to the center of the edge, follow your normal up to 10 units, make the parallel lines (infinite length) and find where they intersect the neighbour parallel-line, which will be a waypoint.

Picture says more than a thousand words, so here you go:

Hope this helps.

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Lemon

Senior Newbie

Java games rock!

 « Reply #2 - Posted 2005-09-23 10:01:47 »

I will try that

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Jeff

JGO Coder

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 « Reply #3 - Posted 2005-09-23 22:32:09 »

I actually wrote code that did exactly this awhile ago.

Slight difference in order that coems otu to the same thing:  I found the normals of the two conencting edges and averged them to get a normal at the corner and then multipled that unit vector by the required distance from the corner to find the new corner point.

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Riven
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 « Reply #4 - Posted 2005-09-23 23:40:38 »

Well that would have been easier yes, but he wanted parallel lines, that's why it's all slightly more complex.

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Jeff

JGO Coder

Got any cats?

 « Reply #5 - Posted 2005-09-24 04:31:41 »

Well that would have been easier yes, but he wanted parallel lines, that's why it's all slightly more complex.

ah, missed that requirement.

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Lemon

Senior Newbie

Java games rock!

 « Reply #6 - Posted 2005-09-30 03:35:23 »

Well I've got that sorted and everything is working well.

I've got another question though, this ones involving threads.

I'm quite confused about how I should be going about this. Should I create a new class that holds all the data and is a MouseListener and ActionListener and have both this class and the LoadingScreen within the JPanel?

Thanks
Simon
Riven
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Exp: 16 years

 « Reply #7 - Posted 2005-09-30 09:08:35 »

Yes, definitly seperate your data from your GUI. You'll save yourself from a lot of trouble and it'll make your application a lot clearer. Once you seperated it, you'll find it much eachier to do your threading.

Basicly you want this:
onClick -> spawn new Thread that does the heavy task.
periodicly check (every 100ms?)  that new thread changed some variable - possibly now containing the result of the calculation - to notify it's finished.
when you found that the thread has done it's job, grab the results from that variable and paint it.

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