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# Intersection of lines - optimization if perpendicular?

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Hello dear community, I can figure out the point of intersection of 2 lines. Now I have 2 lines which I know are perpendicular to each other! Is there a opzimization for finding the point of intersection in this special case? Thanks! Nathan

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Are the lines guaranteed to be perpendicular before entering the function that calculates the intersection? Only in that case the optimization is worthwhile since otherwise the perpendicular case is just an arbitrary case to optimize for.

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I can think of one 'optimisation'. Probably not worth it, unless it's really special (axis aligned lines).

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Quote:
 Original post by arithmaAre the lines guaranteed to be perpendicular before entering the function that calculates the intersection? Only in that case the optimization is worthwhile since otherwise the perpendicular case is just an arbitrary case to optimize for.

Yes, they always are perpendicular.

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If the two lines are perpendicular and you have two initial points on them then the problem boils to projecting a point on another line.

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Vector IntersectPerpendicularLines(const Vector& A0, const Vector& A1, const Vector& B0, const Vector& B1){    Vector A = A1 - A0;    Vector D = B0 - A0;    float ad = A.DotProduct(D);    float a2 = A.DotProduct(A);    return A0 + A * (ad / a2);}

[Edited by - oliii on March 22, 2007 6:23:01 PM]

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Quote:
 Original post by oliii *** Source Snippet Removed ***

That's a great example of why documentation and testing are such a good idea... [smile]

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Quote:
 Original post by arithmaIf the two lines are perpendicular and you have two initial points on them then the problem boils to projecting a point on another line.

That makes sense! Thanks for the help!
And thanks for the code-example, Oliii!

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Quote:
Original post by jjd
Quote:
 Original post by oliii *** Source Snippet Removed ***

That's a great example of why documentation and testing are such a good idea... [smile]

Heh, I usually do. but that should work (I think) [grin]

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It shouldn't even compile. ^_^

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