I am developing a heat map image generator and I have come to 2 solutions to calculate the intensity in a given point within a distance from the heat source:
The first one is similar to wave dispersion:
intensity = 1 / math.pow(1 + distance, 2)
The second one looks nice on the screen, but I invented it myself
intensity = math.pow(2, -distance)
I don't know if any of the solutions above are near the real world behavior.