Quadrilateral

quadrilateral is an implementation of the diamond-square algorithm extended to support rectangles.

corner randomization strength controls how much the initial four seed values vary.

initial randomization strength is how much averages get perturbed by to begin with.

rand falloff indicates how much the randomization amount should be reduced by each step. this falloff is exponential: a value of 1 halves the randomization strength each step, a value of 2 quarters it, etc.

midpoint x and midpoint y determine where the center of the square is. a value of 0.5 for each results in the square being divided into four equal sub-squares each step (i.e., the normal diamond-square algorithm.) 0,0 is the top left corner of the square, and 1,1 is the bottom right corner.

low end and high end control how bright the image is. the average height in the final result will always render as a neutral grey. low end controls how many standard deviations away black is from that. same with high end and white.

generate creates a new heightmap. redraw draws the previously generated heightmap with the new settings.