public Texture2D GenerateTexture(bool makeNoLongerReadable = false)
{
    Texture2D tex = new Texture2D(1, (int)_GradientResolution, TextureFormat.ARGB32, false, true);
    tex.wrapMode = WrapMode;
    tex.filterMode = FilterMode.Bilinear;
    tex.anisoLevel = 1;
    Color[] colors = new Color[(int)_GradientResolution];
    float div = (float)(int)_GradientResolution;
    for (int i = 0; i < (int)_GradientResolution; ++i)
    {
      float t = (float)i/div;
      colors[i] = _Gradient.Evaluate(t);
    }
    tex.SetPixels(colors);
    tex.Apply(false, makeNoLongerReadable);
    return tex;
}

v2f vert (appdata v)
{
  const float PI = 3.14159;
  v2f o;
  o.vertex = UnityObjectToClipPos(v.vertex);
  o.color = v.color;
  o.uv = TRANSFORM_TEX(v.uv, _MainTex);
  o.uv.xy -= 0.5;
  float s = sin (2 * PI * (-v.uv2.x) /360);
  float c = cos (2 * PI * (-v.uv2.x) /360);
  float2x2 rotationMatrix = float2x2( c, -s, s, c);
  rotationMatrix *=0.5;
  rotationMatrix +=0.5;
  rotationMatrix = rotationMatrix * 2-1;
  o.uv.xy = mul (o.uv.xy, rotationMatrix );
  o.uv.xy += 0.5;
  return o;
}

fixed4 SampleSpriteTexture (float2 uv)
{
  fixed4 color = tex2D (_MainTex, uv);
#if UNITY_TEXTURE_ALPHASPLIT_ALLOWED
  if (_AlphaSplitEnabled)
  color.a = tex2D (_AlphaTex, uv).r;
#endif //UNITY_TEXTURE_ALPHASPLIT_ALLOWED
  return color;
}
fixed4 frag (v2f i) : SV_Target
{
  fixed4 col = SampleSpriteTexture ( i.uv) * i.color;
  return col;
}

v2f vert (appdata v)
{
  v2f o;
  o.vertex = UnityObjectToClipPos(v.vertex);
  o.color = v.color;
  o.uv = TRANSFORM_TEX(v.uv, _MainTex);
  o.center = v.center;
  return o;
}
fixed4 frag (v2f i) : SV_Target
{
  const float PI = 3.14159;
  float x =  (i.uv.x - i.center.x);
  float y =  (i.uv.y - i.center.y);
  float angle = acos(dot(float2(0, 1),normalize(float2(x, y))));
  float sign = (x) / abs(x);
  float TwoPI = PI * 2;
  float2 uv = ( sign*angle - i.center.z / 360 * TwoPI) / TwoPI;
  fixed4 col = SampleSpriteTexture (uv) * i.color;
  return col;
}

v2f vert (appdata v)
{
  const float PI = 3.14159;
  v2f o;
  o.vertex = UnityObjectToClipPos(v.vertex);
  o.color = v.color;
  o.uv = TRANSFORM_TEX(v.uv, _MainTex);
  float s = sin (2 * PI * (-v.params.z) /360);
  float c = cos (2 * PI * (-v.params.z) /360);
  float2x2 rotationMatrix = float2x2( c, -s, s, c);
  rotationMatrix *=0.5;
  rotationMatrix +=0.5;
  rotationMatrix = rotationMatrix * 2-1;
  o.uv.xy = mul (o.uv.xy - v.center.xy, rotationMatrix );
  o.params = v.params;
  o.center = v.center;
  return o;
}
fixed4 frag (v2f i) : SV_Target
{
  float x =  i.uv.x;
  float y =  i.uv.y;
  float r1 = i.params.x / 2;
  float r2 = i.params.y / 2;
  float2 uv = sqrt(x * x / r1 + y * y / r2);
  fixed4 col = SampleSpriteTexture (uv) * i.color;
  return col;
}

fixed4 frag (v2f i) : SV_Target
{
  float x =  i.uv.x;
  float y =  i.uv.y;
  float r1 = i.params.x / 2;
  float r2 = i.params.y / 2;
  float2 uv = abs(x) / r1 + abs(y) / r2;
  fixed4 col = SampleSpriteTexture (uv) * i.color;
  return col;
}