Product of 2 polygons.
BlitzMax Forums/BlitzMax Programming/Product of 2 polygons.
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| This may sound wierd but I would like some code to add together two polygons giving one polygon as the result. Each polygon is made of array data points. The format is array[x,y,x2,y2.....] I'm not very good at making agorithems, I thought it might first check for line intersections, then divide the line into two lines, these would be saved as temp vars. If either of the two lines resides within a polygon delete the line segment. Then the data of lines is saved into a temp var list and returned. THis might not work and I have no idea how to impliment it. I have something very innovative planned for this.  |
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| Something like this should be quite easy to realize using ScanLine algorithms as it will notify you when you reach a point "within". It will also tell you the intersection point when it reaches it. Using those data should enable you to easily drop the "within vertices" for the edge ones. *I'm sure there are more efficient methods after all. But using Scanline is quite efficient and at least easy to understand what it does ^^* |
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| You can also do this by creating BSP trees for each of your polygons lines. From those trees you can send each line down the other's tree - splitting it where is intersects and keeping/throwing away the portions outside/inside. Then you put all lines left into a new polygon by matching up joining ends and finally reduce the lines by joining those which are inline. There may be more efficient methods like Dreamora says, I expect there is a more efficient scanline method, but I personally have done this with BSP without much fuss. (C++ I'm afraid and the code doesn't belong to me) |
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| Hmm, BSP is a good idea I think. http://www.3dtechdev.com/tutorials/illegalgeometry/illegalgeometrytut.html Put these 2 polygons together as 1 polygon, build a BSP tree of it and remove illegal geometry. cu olli |
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| Great link! |
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| Thanks for all your help guys. :) |
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