about actor color Interpolate

I colored the actor with the following codes:
data = actor.GetMapper().GetInput()

How to make the bounds clearly without Interpolate like the following pic.

SetInterpolateScalarsBeforeMapping may not useful…

Creating a LUT with 2 colors and using SetInterpolateScalarsBeforeMapping seems to work for me. Test:

from vedo import *
cub = CubicGrid(n=(20,20,20)).alpha(1).lw(1)
arr = cub.points()[:,0]
lut = buildLUT([(0.42,'red'), (1,'white')])
cub.cmap(lut, arr).show(axes=1)