Geometrie conventions for computational techniques that speed up the thermal model computation. Top: The red surface represents all geometric configurations of the angles i, e, and ψ that describe the lunar surface seen by GF-4 on July 25, 2018. The black dots indicate the sampling points we evaluate the thermal model. Bottom: Example for self-heating on periodic fractal surfaces. A red square encircles the original fractal surface of 200 × 200 pixels. Outside the red square, it is repeated periodically. A white X marks the pixel of interest. The red pixels within the red square directly illuminate X for a given self-heating radius of 100 pixels. When assuming periodicity, the blue pixels within the original fractal are transported to the yellow pixel positions. Now, X receives a realistic amount of self-heating radiation, even though it is located at the edge of the original fractal surface.