public void ComputeTransferFunction()
        {
            Vector4[] transferFunc = new Vector4[256];
            Cubic[]   colorCubic   = Cubic.CalculateCubicSpline(mColorKnots.Count - 1, mColorKnots);
            Cubic[]   alphaCubic   = Cubic.CalculateCubicSpline(mAlphaKnots.Count - 1, mAlphaKnots);

            int numTF = 0;

            for (int i = 0; i < mColorKnots.Count - 1; i++)
            {
                int steps = mColorKnots[i + 1].IsoValue - mColorKnots[i].IsoValue;

                for (int j = 0; j < steps; j++)
                {
                    float k = (float)j / (float)(steps - 1);

                    transferFunc[numTF++] = colorCubic[i].GetPointOnSpline(k);
                }
            }

            numTF = 0;
            for (int i = 0; i < mAlphaKnots.Count - 1; i++)
            {
                int steps = mAlphaKnots[i + 1].IsoValue - mAlphaKnots[i].IsoValue;

                for (int j = 0; j < steps; j++)
                {
                    float k = (float)j / (float)(steps - 1);

                    transferFunc[numTF++].w = alphaCubic[i].GetPointOnSpline(k).w;
                }
            }
            for (int i = 0; i < colorarray.Length; i++)
            {
                // Debug.Log(i+" "+transferFunc[i]);
                if (transferFunc[i].w > 1)
                {
                    transferFunc[i].w = 1;
                }
                if (transferFunc[i].w < alphaValueThreadshold)
                {
                    transferFunc[i].w = 0;
                }
                colorarray[i] = transferFunc[i];
                //Debug.Log(i + " " + transferFunc[i]);
            }
            //  material.SetColorArray("_ColorArray", colorarray);
        }