Cylinder Orientation between two points on a sphere, Scenekit, Quaternions IOS

Question

I\'ve been trying to draw a cylinder between two points on the outer edge of a sphere using SceneKit. I have already produced a line between these two points using primitive

Answer 1

I have been looking for a solution to make cylinder between two points and thanks to rickster, I have used his answer to make SCNNode extension. There, I have added missing conditions for a possible cylinder orientation to avoid its wrong opposite direction.

func makeCylinder(positionStart: SCNVector3, positionEnd: SCNVector3, radius: CGFloat , color: NSColor, transparency: CGFloat) -> SCNNode
{
    let height = CGFloat(GLKVector3Distance(SCNVector3ToGLKVector3(positionStart), SCNVector3ToGLKVector3(positionEnd)))
    let startNode = SCNNode()
    let endNode = SCNNode()

    startNode.position = positionStart
    endNode.position = positionEnd

    let zAxisNode = SCNNode()
    zAxisNode.eulerAngles.x = CGFloat(M_PI_2)

    let cylinderGeometry = SCNCylinder(radius: radius, height: height)
    cylinderGeometry.firstMaterial?.diffuse.contents = color
    let cylinder = SCNNode(geometry: cylinderGeometry)

    cylinder.position.y = -height/2
    zAxisNode.addChildNode(cylinder)

    let returnNode = SCNNode()

    if (positionStart.x > 0.0 && positionStart.y < 0.0 && positionStart.z < 0.0 && positionEnd.x > 0.0 && positionEnd.y < 0.0 && positionEnd.z > 0.0)
    {
        endNode.addChildNode(zAxisNode)
        endNode.constraints = [ SCNLookAtConstraint(target: startNode) ]
        returnNode.addChildNode(endNode)

    }
    else if (positionStart.x < 0.0 && positionStart.y < 0.0 && positionStart.z < 0.0 && positionEnd.x < 0.0 && positionEnd.y < 0.0 && positionEnd.z > 0.0)
    {
        endNode.addChildNode(zAxisNode)
        endNode.constraints = [ SCNLookAtConstraint(target: startNode) ]
        returnNode.addChildNode(endNode)

    }
    else if (positionStart.x < 0.0 && positionStart.y > 0.0 && positionStart.z < 0.0 && positionEnd.x < 0.0 && positionEnd.y > 0.0 && positionEnd.z > 0.0)
    {
        endNode.addChildNode(zAxisNode)
        endNode.constraints = [ SCNLookAtConstraint(target: startNode) ]
        returnNode.addChildNode(endNode)

    }
    else if (positionStart.x > 0.0 && positionStart.y > 0.0 && positionStart.z < 0.0 && positionEnd.x > 0.0 && positionEnd.y > 0.0 && positionEnd.z > 0.0)
    {
        endNode.addChildNode(zAxisNode)
        endNode.constraints = [ SCNLookAtConstraint(target: startNode) ]
        returnNode.addChildNode(endNode)

    }
    else
    {
        startNode.addChildNode(zAxisNode)
        startNode.constraints = [ SCNLookAtConstraint(target: endNode) ]
        returnNode.addChildNode(startNode)
    }

    return returnNode
}