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On Selection of the Wave Spectrum in Ocean Wave Real-time Rendering

Abstract: The Phillips spectrum is widely used in ocean wave real-time rendering. First, the#br# structure of the spectrum is analyzed. The Phillips spectrum is an instantaneous spatial spectrum.#br# Its frequency spectrum is in accord with the spectrum form raised by Neumann and similar to the#br# P-M spectrum. Its directional distribution function is that recommended by the international#br# towing tank conference. On the hypothesis that the wave energy per unit area of the Phillips#br# spectrum equals that of the P-M spectrum, the spectral constant is computed, and the spectral wind#br# speed is clarified. In addition to the Phillips spectrum, other spectra are tried as well. The P-M#br# spectrum and the directional distribution function of cos-2s form are used to construct an#br# instantaneous spatial spectrum, denoted as PM-cos2s form, and the JONSWAP spectrum and the#br# direction distribution function of Poisson form are applied for constructing an instantaneous#br# spatial spectrum, denoted as J-Po from. The comparison of the rendering results of the three#br# spectra shows that the wave rendered with the Phillips spectrum and PM-cos2s spectrum can#br# reflect wind speed influence on the wave, but cannot embody the fetch length influence, while the#br# wave rendered with J-Po spectrum can show the fetch length effect along with wind speed on the wave. With the same computer hardware, the frame rates of the three spectra are equal. For wave#br# rendering in the nautical simulator, the wind parameter of the selected spectrum should contain the#br# wind speed as well as fetch length, and the generated wave of the spectrum should distribute in#br# (-?,?] of the wind speed. So J-Po spectrum is more suitable than the other two for the nautical#br# simulator. The method was used in the nautical simulator.#br# Key words: ocean wave rendering; Phillips spectrum; directional distribution function; wind#br# speed   

  • Online:2015-04-30 Published:2015-03-30

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Abstract: The Phillips spectrum is widely used in ocean wave real-time rendering. First, the
structure of the spectrum is analyzed. The Phillips spectrum is an instantaneous spatial spectrum.
Its frequency spectrum is in accord with the spectrum form raised by Neumann and similar to the
P-M spectrum. Its directional distribution function is that recommended by the international
towing tank conference. On the hypothesis that the wave energy per unit area of the Phillips
spectrum equals that of the P-M spectrum, the spectral constant is computed, and the spectral wind
speed is clarified. In addition to the Phillips spectrum, other spectra are tried as well. The P-M
spectrum and the directional distribution function of cos-2s form are used to construct an
instantaneous spatial spectrum, denoted as PM-cos2s form, and the JONSWAP spectrum and the
direction distribution function of Poisson form are applied for constructing an instantaneous
spatial spectrum, denoted as J-Po from. The comparison of the rendering results of the three
spectra shows that the wave rendered with the Phillips spectrum and PM-cos2s spectrum can
reflect wind speed influence on the wave, but cannot embody the fetch length influence, while the
wave rendered with J-Po spectrum can show the fetch length effect along with wind speed on the wave. With the same computer hardware, the frame rates of the three spectra are equal. For wave
rendering in the nautical simulator, the wind parameter of the selected spectrum should contain the
wind speed as well as fetch length, and the generated wave of the spectrum should distribute in
(-,] of the wind speed. So J-Po spectrum is more suitable than the other two for the nautical
simulator. The method was used in the nautical simulator.

Key words: ocean wave rendering, Phillips spectrum, directional distribution function, wind
speed