检查3D空间中两条线段是否相交

Question

I'm trying to find if two line segments intersects in 3D space. Both segments are given by points (x1, y1, z1) and (x2, y2, z2). The following artcile describes how to do it in 2D space: https://www.geeksforgeeks.org/check-if-two-given-line-segments-intersect/ but I have no clue how to distinguish points orientation in 3D space (if they are clockwise or counter-clockwise). Thanks in advance.

Answer 1

Calculate direction vectors d1 and d2 for both segments ( d1.x = x12-x11 and so on, where x11 is starting point of the first segment, x12 is ending point)

Calculate starting points difference ( bx = x21 - x11 and so on)

Find

p = (d1 x d2) (vector product)

If p is zero vector, then lines are parallel.

If lines do intersect, (b.dot.p) should be = 0 (scalar product), else these lines are skew.

Intersection point:

ip = point11 + d1 * [ (b x d2).dot.p / (p.dot.p) ]

Note that value in [] should be in range 0..1 , otherwise lines intersect outside of segments.

Seems similar approach is described in wiki