Animating While Trimming the Spikes of the Figure

clearvars;
close all;
clc;

x = 0:50;
y = rand(1,length(x));
plot(x,y);

I want to trim the spikes of the figure at y=0.5, but while doing it, I want to animate the trim with a triangle (as a tool cuts the spikes with a knife).

Can anyone please help me with this?

Thank you