Draw SceneKit object between two points

Question

Having made some progress in the geometry side of things I\'m moving on to putting together an entire scene. That scene has a couple dozen objects, each defined by a boundin

Answer 1

Sprout's (wow, the autocorrect will not allow me to actually type in his name!) post is indeed a solution, but I have implemented a very different solution in my code.

What I do is calculate the length of the line and the two endpoints, based on the X, Y and Z locations from the two ends:

let w = SCNVector3(x: CGFloat(x2m-x1m), y: CGFloat(y2m-y1m), z: CGFloat(z2m-z1m))
let l = w.length()

The length is simply pythag. Now I make an SCNNode that will hold the SCNCylinder, and position it in the middle of the line:

    let node = SCNNode(geometry: cyl)
    node.position = SCNVector3(x: CGFloat((x1m+x2m)/2.0), y: CGFloat((y1m+y2m)/2.0), z: CGFloat((z1m+z2m)/2.0))

And now the nasty part, where we calculate the Euler angles and rotate the node:

    let lxz = (Double(w.x)**2 + Double(w.z)**2)**0.5
    var pitch, pitchB: Double
    if w.y < 0 {
        pitchB = M_PI - asin(Double(lxz)/Double(l))
    } else {
        pitchB = asin(Double(lxz)/Double(l))
    }
    if w.z == 0 {
        pitch = pitchB
    } else {
        pitch = sign(Double(w.z)) * pitchB
    }
    var yaw: Double
    if w.x == 0 && w.z == 0 {
        yaw = 0
    } else {
        let inner = Double(w.x) / (Double(l) * sin (pitch))
        if inner > 1 {
            yaw = M_PI_2
        } else if inner < -1 {
            yaw = M_PI_2
        } else {
            yaw = asin(inner)
        }
    }
    node.eulerAngles = SCNVector3(CGFloat(pitch), CGFloat(yaw), 0)

I suspect there is a much simpler way to do this using one of the other rotation inputs, but this works and working is a feature!