addTextureShaderToChild.Swift

func addTextureShaderToChild(child:SCNNode) {
  let program = SCNProgram()
  program.fragmentFunctionName = "TextureSurfaceFragment"
  program.vertexFunctionName = "TextureVertexShader"
  program.isOpaque = false;

  // CREATE A MATERIAL, ADD THE PROGRAM, AND ADD IT TO THE CHILD.
  let shaderMaterial = SCNMaterial()
  shaderMaterial.program = program;
  shaderMaterial.transparencyMode = .rgbZero;
  shaderMaterial.blendMode = .alpha;
  shaderMaterial.writesToDepthBuffer = false
  shaderMaterial.readsFromDepthBuffer = false
  shaderMaterial.cullMode = .back

  let image = UIImage(named: "YOUR_TEXTURE")!
  let imageProperty = SCNMaterialProperty(contents: image)
  // The name you supply here should match the texture parameter name in the fragment shader
  shaderMaterial.setValue(imageProperty, forKey: "diffuseTexture")

  child.geometry?.materials.removeAll();
  child.geometry?.materials = [shaderMaterial];
}