float sCircleHeightInPixel = 100;
float sCircleWidthInPixel = 100;
float sBorderWidthInPixel = 10;
float sAngleStart = -3.14;
float sAngleEnd = 3.14;
float sSmoothness = 0.005; // Menos suavização

float4 PixelShaderFunction(float4 Diffuse : COLOR0, float2 TexCoord : TEXCOORD0) : COLOR0
{
    float2 uv = float2( TexCoord.x, TexCoord.y ) - float2( 0.5, 0.5 );

    float angle = atan2( -uv.x, uv.y );  // -PI to +PI
    if ( sAngleStart > sAngleEnd )
    {
        if ( angle < sAngleStart && angle > sAngleEnd )
            return 0;
    }
    else
    {
        if ( angle < sAngleStart || angle > sAngleEnd )
            return 0;
    }

    float2 vec = normalize( uv );
    float CircleRadiusInPixel = lerp( sCircleWidthInPixel, sCircleHeightInPixel, vec.y * vec.y );
    float borderWidth = sBorderWidthInPixel / CircleRadiusInPixel;

    float dist = sqrt( dot( uv, uv ) );
    
    // Definição da borda
    float edge1 = 0.5 - borderWidth; // Borda interna
    float edge2 = 0.5;               // Borda externa

    float alpha = smoothstep(edge1 - sSmoothness, edge1 + sSmoothness, dist) *
                  (1.0 - smoothstep(edge2 - sSmoothness, edge2 + sSmoothness, dist));

    return Diffuse * alpha;
}

technique tec0
{
    pass P0
    {
        PixelShader = compile ps_2_0 PixelShaderFunction();
    }
}