CODEWITHSUNDEEP
mathgeometrylinesbeziercurves
Robin Rodricks
Robin Rodricks

Reputation: 113976

How do you calculate if 2 lines are facing toward or away?

Given the 4 points describing 2 lines, how do you quickly calculate if line A is facing towards or away from line B?

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Similarly, how to check if line A is towards or away from quadratic bezier curve B?

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Upvotes: 4

Views: 2249

Answers (1)

duffymo
duffymo

Reputation: 308763

Take the dot product of the unit vector of the candidate line and the unit normal pointing in the direction you wish for the other (there are two unit normal vectors).

If the dot product is positive, it's "away"; "towards" is negative.

If you don't know vectors, get an intro text and read up on them.

Upvotes: 4

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