static nthVertex(y, n) {
        const kR = HctSolver.Y_FROM_LINRGB[0];
        const kG = HctSolver.Y_FROM_LINRGB[1];
        const kB = HctSolver.Y_FROM_LINRGB[2];
        const coordA = n % 4 <= 1 ? 0.0 : 100.0;
        const coordB = n % 2 === 0 ? 0.0 : 100.0;
        if (n < 4) {
            const g = coordA;
            const b = coordB;
            const r = (y - g * kG - b * kB) / kR;
            if (HctSolver.isBounded(r)) {
                return [r, g, b];
            }
            else {
                return [-1.0, -1.0, -1.0];
            }
        }
        else if (n < 8) {
            const b = coordA;
            const r = coordB;
            const g = (y - r * kR - b * kB) / kG;
            if (HctSolver.isBounded(g)) {
                return [r, g, b];
            }
            else {
                return [-1.0, -1.0, -1.0];
            }
        }
        else {
            const r = coordA;
            const g = coordB;
            const b = (y - r * kR - g * kG) / kB;
            if (HctSolver.isBounded(b)) {
                return [r, g, b];
            }
            else {
                return [-1.0, -1.0, -1.0];
            }
        }
    }
Returns the nth possible vertex of the polygonal intersection.

@param y The Y value of the plane.
@param n The zero-based index of the point. 0 <= n <= 11.
@return The nth possible vertex of the polygonal intersection
of the y plane and the RGB cube, in linear RGB coordinates, if
it exists. If this possible vertex lies outside of the cube,
[-1.0, -1.0, -1.0] is returned.