kernel RadialVectors : ImageComputationKernel<ePixelWise>
{
  Image<eRead, eAccessPoint, eEdgeClamped> src;  //the input image
  Image<eWrite> dst;  //the output image

  param:
    float ratio;  //This parameter is made available to the user.
    float2 center;
    float protect;
    float rotate;
    float gamma;
    float multiply;
    float2 size;

  local:

    float _imgDiag; //Image diagonal

  //In define(), parameters can be given labels and default values.
  void define() {
    defineParam(ratio, "Aspect Ratio", 1.0f);
    defineParam(center, "Center", float2(1.0f,1.0f));
    defineParam(protect, "Protect Center", 0.0f);
    defineParam(rotate, "Rotate Vectors", 0.0f);
    defineParam(gamma, "Gamma", 1.0f);
    defineParam(multiply, "Multiply", 1.0f);
  }

  //The init() function is run before any calls to kernel().
  void init() {
    _imgDiag = length(size);
  }

  //The kernel function is run at every pixel to produce the output.
  void process(int2 pos) {
    //float2 posf = float2(pos.x, pos.y);
    float2 posf = float2(src(0)*size.x, src(1)*size.y);
    float2 v = posf-center;
    v = v/(_imgDiag/2.0f);

    // Edit vector magnitude: Blackpoint+clamp for protecting center
    if (protect < (1.0f)){ //If we protect the whole image then we don't need to output any vectors
      // Edit aspect Ratio
      v = float2(v.x, v.y * ratio);
      // Find vector Magnitude so that can be edited
      float magv = length(v);

      magv = max((magv - protect) / (1.0f-protect),0.0f);
      magv = pow(magv, 1.0f/gamma);
      float2 normv;
      if (magv>0.0f){
        normv = normalize(v);
      }
      else {
        normv = float2(1.0f, 0.0f);
      }
      v = normv * magv;
      // Rotate Normals
      if (rotate != 0.0f){
        float r = rotate * 3.141592653589793f / 180.0f;
        v = float2( v.x * cos(r) - v.y * sin(r), v.x * sin(r) + v.y * cos(r));
      }
      // Multiply Output
      //v = v * (_imgDiag/4) * multiply;
      v = v * multiply;
      dst() = float4(v.x, v.y, 0.0f, 0.0f);
      //dst() = float4(magv, magv, magv, 0.0f);
    }
    else{
      dst() = float4(0.0f);
    }

   }
};