L3DT users' wiki
Large 3D terrain generator



Plugin information

Author Aaron
Description A plugin to calculate the fast Fourier transform (FFT) of the heightfield, and the inverse transform.
Download link atCalc_FFT-bin.zip (135kB)
Source code Available on request.
DLL version v2.7.1.0 (26th of March 2009).
Dependencies L3DT build 2.7 or later.

Using atCalc_FFT

Applying the forward transform

To calculate the fast Fourier transform (FFT) of the heightfield, select the 'Extensions→atCalc_FFT→Calculate FFT of heightfield' menu option. The output will be two maps called “HF_FFT_Amplitude” and “HF_FFT_Phase”, which will be added to your project. For a typical noisy heightfield, these maps will look like:

:plugins:calc:atcalc_fft:fft_amp.png :plugins:calc:atcalc_fft:fft_phase.png
Amplitude component Phase component

Note that both maps are normal floating-point maps. The phase map appears in colour because the default palette for the phase map is “rainbow”, which maps the -PI→PI value range into a blue→red colour range.

Applying the inverse transform

To calculate the inverse transform, select the 'Extensions→atCalc_FFT→Calculate heightfield from inverse FFT' menu option. This will overwrite the heightfield by inverse-transforming the “HF_FFT_Amplitude” and “HF_FFT_Phase” maps created by the previous use of the 'Calculate FFT of heightfield' menu option (see above).

The output of the inverse transform of the amplitude/phase images is a hightfield such as this:

Heightfield from inverse FFT


The atCalc_FFT plugin will only work on square heightfields that are a power of two. This is a requirement of the FFT algorithm. If you want to transform heightfields of different sizes, you should look into implementing the general (and really slow) Fourier transform algorithm.



  • Released v2.7.1.0
  • Changed function arguments from VarID_maps to VarID_hvars.
  • Updated to Zeolite v2.7.1.


  • Released v2.5.4.0
  • Added menu entries.
  • Changed FFT components from re/im to amplitude/phase.
  • Moved origin to centre of FFT images.


  • Released v2.3.1.0
plugins/calc/atcalc_fft.txt · Last modified: 2017/08/31 07:04 (external edit)
Except where otherwise noted, content on this wiki is licensed under the following license:CC Attribution-Share Alike 3.0 Unported
Recent changes RSS feed Donate Powered by PHP Valid XHTML 1.0 Valid CSS Driven by DokuWiki