Drawing a line on SceneKit won't work on device - ios

Question

Following this solution: Custom SceneKit Geometry and converted to Swift 3, the code became:
func drawLine() {
var verts = [SCNVector3(x: 0,y: 0,z: 0),SCNVector3(x: 1,y: 0,z: 0),SCNVector3(x: 0,y: 1,z: 0)]
let src = SCNGeometrySource(vertices: &verts, count: 3)
let indexes: [CInt] = [0, 1, 2]
let dat = NSData(
bytes: indexes,
length: MemoryLayout<CInt>.size * indexes.count
)
let ele = SCNGeometryElement(
data: dat as Data,
primitiveType: .line,
primitiveCount: 2,
bytesPerIndex: MemoryLayout<CInt>.size
)
let geo = SCNGeometry(sources: [src], elements: [ele])
let nd = SCNNode(geometry: geo)
geo.materials.first?.lightingModel = .blinn
geo.materials.first?.diffuse.contents = UIColor.red
scene.rootNode.addChildNode(nd)
}
It work on simulator:
But I got error on device:
/BuildRoot/Library/Caches/com.apple.xbs/Sources/Metal/Metal-85.83/ToolsLayers/Debug/MTLDebugRenderCommandEncoder.mm:130: failed assertion `indexBufferOffset(0) + (indexCount(4) * 4) must be <= [indexBuffer length](12).'
What is happening?
The entire code is here: Source code

Answer 1

I'm answering my own question because I found a solution that can help others.
The problem was on "indexes", 3 indexes won't draw 2 vertices. Must set 2 indexes for each vertice you want to draw.
This is the final function:
func drawLine(_ verts : [SCNVector3], color : UIColor) -> SCNNode? {
if verts.count < 2 { return nil }
let src = SCNGeometrySource(vertices: verts, count: verts.count )
var indexes: [CInt] = []
for i in 0...verts.count - 1 {
indexes.append(contentsOf: [CInt(i), CInt(i + 1)])
}
let dat = NSData(
bytes: indexes,
length: MemoryLayout<CInt>.size * indexes.count
)
let ele = SCNGeometryElement(
data: dat as Data,
primitiveType: .line,
primitiveCount: verts.count - 1,
bytesPerIndex: MemoryLayout<CInt>.size
)
let line = SCNGeometry(sources: [src], elements: [ele])
let node = SCNNode(geometry: line)
line.materials.first?.lightingModel = .blinn
line.materials.first?.diffuse.contents = color
return node
}
Calling:
scene.rootNode.addChildNode(
drawLine(
[SCNVector3(x: -1,y: 0,z: 0),
SCNVector3(x: 1,y: 0.5,z: 1),
SCNVector3(x: 0,y: 1.5,z: 0)] , color: UIColor.red
)!
)
Will draw: