Feature point in polygon #57
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server/src/util.c
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| * \brief rayFromPointIntersectsLine checks whether ray in X axis direction from point intersects |
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Do you mean a ray that starts in an (x,y) coordinate and travels in positive X-direction, parallell to the x-axis?
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| // Compare the slopes of the lines AB and AP - if the slope of AB is larger than that of AP | ||
| // then a ray in X axis direction will not intersect AB | ||
| if (linePointAX != linePointBX) |
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Might be a bit nitpicky but if the line is vertical, but wouldn't the previous two if-statements have returned a value already? To check this, assume that linePointAX = linePointBX, then it follows that minVal = maxVal which both of the two previous if-statements cover. pointX will always be less than, equal or bigger than minVal.
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I agree, but I would rather have divide-by-zero be explicitly handled so that the code is crystal clear to someone reading it. The machine code will be the same as if I had removed it since the compiler optimises away this check.
server/src/util.c
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| // If the first and last points are different, the polygon segment between them must also be included | ||
| if (verticesX[0] != verticesX[nPtsInPolygon-1] || verticesY[0] != verticesY[nPtsInPolygon-1]) |
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It is in general hard to compare doubles, especially if you want to check that they are equal to each other. Usually you would check that the difference is small enough to count as zero. This could look something like
abs(x-y) < epsilon
where epsilon is some really small number.
Addressed comments
Implemented ray casting algorithm for checking if a point is in a polygon