SceneKit_高级07_SCNProgram用法探究

let scnView = SCNView(frame: self.view.bounds, options: [SCNView.Option.preferredRenderingAPI.rawValue:true])     
scnView.backgroundColor = UIColor.black
self.view.addSubview(scnView)

 let scene = SCNScene()
 scnView.scene = scene

let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
scene.rootNode.addChildNode(cameraNode)

 let ambientLightNode = SCNNode()
 ambientLightNode.light = SCNLight()
 ambientLightNode.light?.type = .ambient
 scene.rootNode.addChildNode(ambientLightNode)

    let text = SCNText(string: "酷走天涯", extrusionDepth: 1)
    text.font = UIFont.systemFont(ofSize: 1)
    let textNode = SCNNode(geometry: text)
    textNode.position = SCNVector3Make(-2, -0.5, -2)
    scene.rootNode.addChildNode(textNode)

 precision mediump float;
varying vec2 v_uv;
void main() {
    gl_FragColor = vec4(1,v_uv,1);
}

attribute vec4 a_srcPos;   // 几何的原来位置
attribute vec2 a_texcoord; // 几何的纹理坐标
uniform mat4 u_mv;    // ModelView 变换矩阵
uniform mat4 u_proj;  // Projection 变换矩阵
uniform float factor; // 渐变因子
varying vec2 v_uv;     // 两个着色器共享纹理坐标
void main()
{
    vec4 vsPos = u_mv * a_srcPos;
    vec2 nrm = vsPos.xz;
    float len = length(vsPos.xz) + 0.0001;
    nrm /= len;
    float a = len + 0.2 * sin(5.0 * vsPos.y + factor * 10.0);
    vsPos.xz = nrm * a;
    gl_Position = u_proj * vsPos  ;
    v_uv = a_texcoord ;
}

 let program = SCNProgram()
 program.isOpaque = false

 let vertexShader   = Bundle.main.url(forResource: "CustomProgram", withExtension:"vsh")
 let fragmentShader = Bundle.main.url(forResource: "CustomProgram", withExtension:"fsh")
 do {
        program.vertexShader =   try String(contentsOf: vertexShader!, encoding: String.Encoding.utf8)
        program.fragmentShader = try String(contentsOf: fragmentShader!, encoding: String.Encoding.utf8)

  }catch{
        print(error)
 }

 program.setSemantic(SCNGeometrySource.Semantic.vertex.rawValue, forSymbol: "a_srcPos", options: nil)
 program.setSemantic(SCNGeometrySource.Semantic.texcoord.rawValue, forSymbol: "a_texcoord", options: nil)

 program.setSemantic(SCNModelViewTransform, forSymbol: "u_mv", options: nil)
 program.setSemantic(SCNProjectionTransform, forSymbol: "u_proj", options: nil)

   textNode.geometry?.firstMaterial?.program = program

 var morphFactor:Float = 0
 textNode.geometry?.firstMaterial?.handleBinding(ofSymbol: "factor", handler:  { (programID, location, renderedNode, renderer)  in
     morphFactor += 0.01
     glUniform1f(GLint(location),  morphFactor);
  })

    textNode.geometry?.firstMaterial?.writesToDepthBuffer = false
    textNode.geometry?.firstMaterial?.readsFromDepthBuffer = false
    textNode.renderingOrder = 100 // 必须最后渲染

    let move = SCNAction.moveBy(x: 0, y: 0, z: -10, duration: 10)
    textNode.runAction(move)