Breeding Terrains with Genetic Terrain Programming: The Evolution of Terrain Generators

Table 1

GP functions.

Name	Description
$\text{plus}(h_1\mathrm{,}{h}_2)$	Arithmetical functions
$\text{minus}(h_1\mathrm{,}{h}_2)$
$\text{multiply}(h_1\mathrm{,}{h}_2)$
$\text{sin}(h)$	Trigonometric functions
$\text{cos}(h)$
$\text{tan}(h)$
$\text{atan}(h)$
$\text{myLog}(h)$	Returns $0$ if $h=0$ and $\log \hspace{0.17em}(abs(h))$
	otherwise
$\text{myPower}(h_1\mathrm{,}{h}_2)$	Returns $0$ if $h_1^{h_2}$ is $NaN$ or $Inf$, or has imaginary part, otherwise returns $h_1^{h_2}$
$\text{myDivide}(h_1\mathrm{,}{h}_2)$	Returns $h_1$ if $h_2=0$ and $h_1÷h_2$
	otherwise
$\text{myMod}(h_1\mathrm{,}{h}_2)$	Returns $0$ if $h_2=0$ and $\mathrm{mod}\hspace{0.17em}(h_1\mathrm{,}{h}_2)$
	otherwise
$\text{mySqrt}(h)$	Returns $\text{sqrt}(abs(h))$
$\text{negative}(h)$	Returns $-h$
$\text{FFT}(h)$	2D discrete Fourier transform
$\text{smooth}(h)$	Circular averaging filter with $r=5$
$\text{gradient}X(h)$	Returns the gradient ($dh/dx$ or $dh/dy$) of a height map $h$. Spacing between points is assumed to be 1
$\text{gradient}Y(h)$