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As always I need your help. I need to draw a straight line from a start value (declared as SCNVector3) and connected to the position in the real world till the end point.

Can someone explain to me with some lines of code how can I do it? Thank you!

Saurabh Jain
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Pietro Messineo
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1 Answers1

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You'll need to implement: touchesBegan, touchesMoved, touchesEnded, touchesCancelled for your camera view controller. In touchesBegan you will need to make hitTest for current ARFrame in the UITouch location. Then you'll have your startPosition and your lastTouch, which is your start UITouch.

Then you will need to add timer with 0.016_667 interval (60Hz) which will update your last touch position with hitTest when you camera moves. Same you'll do in touchesMoved function. And in touchesMoved you'll also update your lastTouch. So at this point you'll have your startPosition and currentPosition, which is SCNVector3. And you can just redraw SCNCylinder (with 0.001m radius for example) for those positions if you need straight line.

At last step in touchesEnded you'll fix your line, or if touchesCancelled you will remove it and clear lastTouch.

UPD

If you need 2D line on the screen, then you'll need to use projectPoint for your ARSceneView.

3D line drawing

For drawing 3D line you could SCNGeometry use extension:

extension SCNGeometry {
    class func line(from vector1: SCNVector3, to vector2: SCNVector3) -> SCNGeometry {
        let indices: [Int32] = [0, 1]
        let source = SCNGeometrySource(vertices: [vector1, vector2])
        let element = SCNGeometryElement(indices: indices, primitiveType: .line)
        return SCNGeometry(sources: [source], elements: [element])
    }
}

Using:

let line = SCNGeometry.line(from: startPosition, to: endPosition)
let lineNode = SCNNode(geometry: line)
lineNode.position = SCNVector3Zero
sceneView.scene.rootNode.addChildNode(lineNode)
Vasilii Muravev
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  • Thank you very much for the explanation. I have already a touchesBegan and touchesEnded function, but I haven't really got it how can I draw the SCNCylinder and how the code will understand how to connect the starting point to the end point? I will need to set the node 1 on the touchesBegan with the startPosition and the same but with the second node inside the touchesEnded? – Pietro Messineo Aug 29 '17 at 09:20
  • @PietroMessineo you could try `let line = SCNGeometry.triangleFrom(vector1: startPoint, vector2: startPoint, vector3: endPoint)` and then `let lineNode = SCNNode(geometry: line)` – Vasilii Muravev Aug 29 '17 at 18:23
  • There's a good example: https://stackoverflow.com/questions/35002232/draw-scenekit-object-between-two-points – Vasilii Muravev Aug 29 '17 at 18:26
  • Thank you! I will try it asap ;) – Pietro Messineo Aug 29 '17 at 20:45
  • I don't know why but: " Type 'SCNGeometry' has no member 'triangleFrom' " – Pietro Messineo Aug 30 '17 at 11:17
  • @PietroMessineo see updated answer. I forgot that `triangleFrom` was my extension func :) – Vasilii Muravev Aug 30 '17 at 14:17
  • How to give custom UI for the line.Like showing tape line instead of the line. – sudheer Nov 08 '17 at 09:11