Rounded Box Outline SDF in SparkSL

RoundedBox.sca

//==============================================================================
// Rounded Box Outline SDF
//==============================================================================

float roundedBoxSDF(vec2 CenterPosition, vec2 Size, float Radius)
{
    return length(max(abs(CenterPosition)-Size+Radius,0.0))-Radius;
}

float roundBoxOutline(vec2 size, float thickness, float radius)
{
  vec2 uv = fragment(std::getVertexTexCoord());
  float edgeSoftness   = 0.002;
  float distance       = roundedBoxSDF(uv - vec2(0.5), size/2.0, radius);
  float smoothedAlpha  = 1.0 - smoothstep(-edgeSoftness, edgeSoftness, abs(distance) - thickness);
  
  return smoothedAlpha;
}

vec4 main(vec2 size, float radius) {
    return vec4(roundBoxOutline(size, 0.005, radius), 0., 0., 1.);
}