How to draw line node keep same size in camera as Measure App in iPhone? - swift

Question

I try make an AR app as a Measure default app in iPhone. ( I base on project TBXark/Ruler on github)
I draw startNode, endNode, cylinder line, and SCNText. But I can't manage the scale of size, it only readable in near, and so small when measure far plane detect.
I have 2 question:
How to keep size node, cylinder and text same when draw near or far as Measure App
How to draw scntext with background and align the same direction cylinder line as Measure App.
Here is my Line Node class:
class LineNode: NSObject {
let startNode: SCNNode
let endNode: SCNNode
var lineNode: SCNNode?
let textNode: SCNNode
let sceneView: ARSCNView?
// init func
init(startPos: SCNVector3,
sceneV: ARSCNView,
color: (start: UIColor, end: UIColor) = (UIColor(hexCss: 0xF1B426), UIColor(hexCss: 0xD43278)),
font: UIFont = UIFont.boldSystemFont(ofSize: 8) ) {
sceneView = sceneV
let scale = 1 / 400.0
let scaleVector = SCNVector3(scale, scale, scale)
func buildSCNSphere(color: UIColor) -> SCNSphere {
let dot = SCNSphere(radius: 1)
dot.firstMaterial?.diffuse.contents = color
dot.firstMaterial?.lightingModel = .constant
dot.firstMaterial?.isDoubleSided = true
return dot
}
// startNode
startNode = SCNNode(geometry: buildSCNSphere(color: color.start))
startNode.scale = scaleVector
startNode.position = startPos
sceneView?.scene.rootNode.addChildNode(startNode)
// endNode
endNode = SCNNode(geometry: buildSCNSphere(color: color.end))
endNode.scale = scaleVector
// line with start to end
lineNode = CylinderLine(parent: sceneView!.scene.rootNode,
v1: startNode.position,
v2: endNode.position,
radius: 0.001,
radSegmentCount: 16,
color: UIColor.white)
sceneView?.scene.rootNode.addChildNode(lineNode!)
// text show measure line length
let text = SCNText (string: "--", extrusionDepth: 0.1)
text.font = font
text.firstMaterial?.diffuse.contents = UIColor(hexCss: 0xffa800)
text.firstMaterial?.lightingModel = .constant
text.alignmentMode = CATextLayerAlignmentMode.center.rawValue
text.truncationMode = CATextLayerTruncationMode.middle.rawValue
text.firstMaterial?.isDoubleSided = true
textNode = SCNNode(geometry: text)
textNode.scale = SCNVector3(1 / 500.0, 1 / 500.0, 1 / 500.0)
super.init()
}
// update end node realtime
public func updatePosition(pos: SCNVector3, camera: ARCamera?, unit: MeasurementUnit.Unit = MeasurementUnit.Unit.centimeter) -> Float {
// update endNode
let posEnd = updateTransform(for: pos, camera: camera)
if endNode.parent == nil {
sceneView?.scene.rootNode.addChildNode(endNode)
}
endNode.position = posEnd
// caculate new mid
let posStart = startNode.position
let middle = SCNVector3((posStart.x + posEnd.x) / 2.0, (posStart.y + posEnd.y) / 2.0 + 0.002, (posStart.z + posEnd.z) / 2.0)
// update text measure
let text = textNode.geometry as! SCNText
let length = posEnd.distanceFromPos(pos: startNode.position)
text.string = MeasurementUnit(meterUnitValue: length).roundUpstring(type: unit)
text.materials.first?.diffuse.contents = UIColor.orange
textNode.setPivot()
textNode.position = middle
if textNode.parent == nil {
sceneView?.scene.rootNode.addChildNode(textNode)
}
lineNode?.removeFromParentNode()
lineNode = lineBetweenNodeA(nodeA: startNode, nodeB: endNode)
sceneView?.scene.rootNode.addChildNode(lineNode!)
return length
}
}

Answer 1

I use this to update scale if even if you stay far away it still readable
func updateScaleFromCameraForNodes(_ nodes: [SCNNode], fromPointOfView pointOfView: SCNNode , useScaling: Bool){
nodes.forEach { (node) in
//1. Get The Current Position Of The Node
let positionOfNode = SCNVector3ToGLKVector3(node.worldPosition)
//2. Get The Current Position Of The Camera
let positionOfCamera = SCNVector3ToGLKVector3(pointOfView.worldPosition)
//3. Calculate The Distance From The Node To The Camera
let distanceBetweenNodeAndCamera = GLKVector3Distance(positionOfNode, positionOfCamera)
let a = distanceBetweenNodeAndCamera*1.75
if(useScaling) {
node.simdScale = simd_float3(a,a,a)
}
}
SCNTransaction.flush()
}
then called it in the renderer updateAtTime
self.updateScaleFromCameraForNodes(self.nodesAdded, fromPointOfView:
self.cameraNode, useScaling: true)