### What does SageMath use to create the pattern when planes overlap?

When two differently colored planes are plotted on (almost) the same plane, what is the formula that SageMath uses to create the pattern shown in the graph? Here one plane is slightly larger-- which makes SageMath show them both in a way that looks slightly similar to an animal print. Also, as you move/manipulate the graph with the mouse, the pattern changes. What formula or information does SageMath use to show the pattern?

I used the Sage Cell Server online to plot this:

sage: M = implicit_plot3d(lambda x,y,z: x, (-15,15), (-15,15), (-15,15), rgbcolor= (0.0, 1.0, 0.0), frame=true)
sage: N = implicit_plot3d(lambda x,y,z: x, (-15,15), (-15,15), (-15,15.5), rgbcolor= (0.0, 0.0, 1.0), frame=true)
sage: M+N

Thanks for any information you can provide!