ength of the gradient of the implicit.
            float grad_dot = 4 * dot(Z, Z);
            // Avoid calling inversesqrt on zero.
            if (bool(medPrecision)) {
                grad_dot = max(grad_dot, 6.1036e-5);
            } else {
                grad_dot = max(grad_dot, 1.1755e-38);
            }
            float approx_dist = implicit * inversesqrt(grad_dot);
            if (bool(medPrecision)) {
                approx_dist *= scale.x;
            }

            half alpha;
            if (edgeType == kFillBW) {
                alpha = approx_dist > 0.0 ? 0.0 : 1.0;
            } else if (edgeType == kFillAA) {
                alpha = saturate(0.5 - half(approx_dist));
            } else if (edgeType == kInverseFillBW) {
                alpha = approx_dist > 0.0 ? 1.0 : 0.0;
            } else {  // edgeType == kInverseFillAA
                alpha = saturate(0.5 + half(approx_dist));
            }
            return inColor * alpha;
        }