Physically accurate real-time synthesis of ocean waves for maritime simulators

Abstract

The most efficient approach to the synthesis of multi-directional ocean waves is the so-called Fourier approach, based on a spectral description of waves in wavenumber space. According to this approach, 2D wavenumber spectra are transformed into spatial wave quantities by means of 2D Inverse Discrete Fourier Transforms. The Fourier approach is well described in literature, but the majority of works dealing with it are focused on graphical realism, and usually neglect the physical accuracy of the synthesized ocean scene. This paper presents a new implementation of the Fourier approach which exploits the equivalence between wavenumber and frequency/direction spectra to result in a flexible, performant and physically accurate model that is especially suitable for maritime simulators. In the proposed method, input wave spectra expressed in frequency/direction space are mapped at runtime on the wavenumber spectra used for the ocean synthesis. A GPU implementation based on the multi-band approach allows highly efficient real-time computations. The performance of the method is described in detail, investigating different configurations of the wavenumber spectrum and comparing the results obtained on different hardware. The physical accuracy is assessed by recording time series of synthesized wave elevations and using them to reconstruct a directional wave spectrum. Four benchmark spectra are examined, highlighting a very satisfactory match between the input and the reconstructed spectra, even for complex sea states with multiple wave systems originated from different sources.