so here is a basic texture being subtracted by a ramp provided by the UV space on it’s red channel
then green
so from here we can attach something that is subtractive to the ramp before it affects the texture
this slider does the trick for visualization and the clamp ensures were are not sending values outside of 0…1
from here we can substitute the maths with multiplies, power of or
‘smoothstep’ & ‘remap’ nodes to do more interesting things - notice subtraction creates a hue shift, this may not be desired.
many ideas i mention are brought up visually here
with the custom vertex stream Shuriken can drive that slider rather than a value on the material
the basic setup of a Custom1.x is here
for basics on how to start using shader graph I found this
