private void Draw()
    {
        Vector3 startPoint = linePath.Evaluate(0f);
        Vector3 endPoint   = linePath.Evaluate(1f);

        // draw line
        var cPointCache = new Vector3[32];

        for (int i = 0; i < cPointCache.Length; i++)
        {
            cPointCache[i] = Vector3.Lerp(startPoint, endPoint, (float)i / (cPointCache.Length - 1));
        }

        for (int i = 0; i < cPointCache.Length - 1; i++)
        {
            Handles.color = Color.Lerp(Color.yellow, Color.magenta, (float)i / cPointCache.Length);
            var lineSegment = new Vector3[2];
            lineSegment[0] = cPointCache[i];
            lineSegment[1] = cPointCache[i + 1];
            Handles.DrawAAPolyLine(lineSegment);
        }

        // draw direction cone cap
        if (!settings.HideDirectionCones &&
            linePath.LocalSpaceTransform.lossyScale != Vector3.zero &&
            linePath.StartPosition != linePath.EndPosition)    // also hide cones if virtually a dot
        {
            float startConeSize = PathEditorUtility.Nice3DHandleSize(startPoint);
            float endConeSize   = PathEditorUtility.Nice3DHandleSize(endPoint);

            Handles.color = Color.yellow;
            Handles.ConeCap(0, startPoint, Quaternion.LookRotation(linePath.Tangent()), startConeSize);
            Handles.color = Color.magenta;
            Handles.ConeCap(0, endPoint, Quaternion.LookRotation(linePath.Tangent()), endConeSize);
        }

        // test t
        Handles.color = PathEditorUtility.GetTColor(settings.EditorData.T);
        if (settings.TestInterpolate)
        {
            Vector3 targetPoint = linePath.Evaluate(settings.EditorData.T);
            float   sphereSize  = PathEditorUtility.Nice3DHandleSize(targetPoint);
            Handles.SphereCap(0, targetPoint, Quaternion.identity, sphereSize);
        }

        // draw GUI
        InterpolateSceneGUI();
        ToolShelf();
    }