Modeling equations, in their simplest form, are arithmetic combinations of image layers assigned to other image layers. Image layers are indicated by a percent sign followed by the layer number. The following equation assigns the average numeric value of image layers 1 and 2 to image layer 3.
%3 = (%1 +%2)/2
The assignment is evaluated for every pixel in image layer 3, using the corresponding pixel values from image layers 1 and 2.
You can also assign a constant value to an entire image layer.
%1 = 255
A standard set of arithmetic operations is available in modeling expressions:
a + b Addition
a - b Subtraction
a * b Multiplication
a / b Division
a ^ b Exponentiation
(a) Parentheses, also square brackets [].
- a Unary negation
The following mathematical intrinsic functions are also available:
sin(), cos(), tan(), asin(), acos(), atan(), ln(), log10(), exp(), exp10(), rad(), deg(), abs(), int(), random() and frac()
All the rules previously indicated for image layers also apply to bitmap layers, except that the variables are prefixed with two percent signs instead of one. A bitmap layer can have a value of either 1 (ON) or 0 (OFF). For example, if image layer 1 has a digital number greater than 50, then set bitmap layer 15 to 1.
If %1 > 50 then
% %15 = 1
endif
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