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unit Fractal;
{***********************************************************
Project: C-evo External Map Generator
Copyright: 1999-2023 P Blackman
License: GPLv3+
Fractal Terrain Generation (fBm sytle textures),
based on algorithms by F. Kenton Musgrave
***********************************************************}
interface
uses Noise;
type
TFBm = class
private
const ExpArraySize = 16;
private
exponent_array: array [1..ExpArraySize] of Double;
fOctaves,
fLacunarity: Double;
public
constructor Create(H: Double; // fractal increment parameter
Lacunarity: Double; // gap between successive frequencies
Octaves: Double; // number of frequencies in the fBm
ResetNoise: Boolean);
function Compute(point: Vector): Double;
end;
implementation uses Math, Noises;
var
Noise3: TNoises;
constructor TfBm.Create
(H: Double; // fractal increment parameter
Lacunarity: Double; // gap between successive frequencies
Octaves: Double; // number of frequencies in the fBm
ResetNoise: Boolean);
var
frequency: Double;
i: Integer;
begin
inherited Create;
if ResetNoise then
Noise3.Free;
fLacunarity := Lacunarity;
// Check that octaves is not too large for exponent array
if Octaves > Pred(ExpArraySize) then
fOctaves := Pred(ExpArraySize)
else
fOctaves := Octaves;
if (Noise3 = nil) OR ResetNoise then
Noise3 := TNoises.Create;
// precompute and store spectral weights
frequency := 1.0;
for i := 1 to 1 + Trunc(fOctaves) do
begin
// compute weight for each frequency
exponent_array[i] := power(frequency, -H);
frequency := frequency * Lacunarity;
end;
end;
function TfBm.Compute(point: Vector): Double;
const distort = 1.9;
var
Value, Remainder: Double;
i: Integer;
begin
Value := 0.0;
for i := 1 to Trunc(fOctaves) do
begin
Value := Value + Noise3.VRNoise3 (point, distort) * exponent_array[i];
point.x := point.x * fLacunarity;
point.y := point.y * fLacunarity;
point.z := point.z * fLacunarity;
end;
Remainder := fOctaves - Trunc(fOctaves);
if ABS(Remainder) > 0.0001 then
// add in ``octaves'' remainder
Value := Value + Remainder * Noise3.VRNoise3(point, distort) * exponent_array[1 + Trunc(fOctaves)];
Result := Value;
end;
end.
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