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I have the following code to create a circle Path and a SCNShape from this path. orbit_gradient.png is a horizontal 1px high image that represents a gradient.

let material = SCNMaterial()  
material.isDoubleSided = true  
material.lightingModel = .constant       
material.diffuse.contents = UIImage(named: "art.scnassets/orbit_gradient.png")  

let shapePath = Path.circle(radius: radius, segments: 512)  

let orbitShape = SCNShape(shapePath)  
orbitShape.materials = [material]    
self.orbitNode.geometry = orbitShape 

The problem I have is that when applying the texture to this geometry I'm just left with a white circle. If I set the diffuse to be UIColor.red it displays as red. What I want to accomplish is a stroked circle that appears to gradually fade, creating a rotating trail effect.

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Got there in the end by using SCNGeometrySource and SCNGeometryElement.

  1. Generate vertices
  2. Generate texture coordinates
  3. Generate indices
  4. Set material (my horizontal, 1px tall gradient)

I made a gist of a class I made incase it's useful to anyone else.

https://gist.github.com/kemalenver/79523e5606f62c5958fcf5e9bedc48a5

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