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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/** \file
* \ingroup bke
*/
#include "BKE_ocean.h"
#include "BLI_math.h"
#include "ocean_intern.h"
#ifdef WITH_OCEANSIM
/* -------------------------------------------------------------------- */
/** \name Ocean Spectrum from EncinoWaves
* \{ */
/*
* Original code from EncinoWaves project Copyright (c) 2015 Christopher Jon Horvath
* Modifications made to work within blender.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*/
/**
* alpha_beta_spectrum is a common algorithm for the Pierson-Moskowitz, JONSWAP and TMA models.
* This is a modified implementation from the EncinoWaves project.
*/
static float alpha_beta_spectrum(const float alpha,
const float beta,
const float gamma,
const float omega,
const float peakomega)
{
return (alpha * sqrt(gamma) / pow(omega, 5.0)) * exp(-beta * pow(peakomega / omega, 4.0));
}
static float peak_sharpen(const float omega, const float m_peakomega, const float m_gamma)
{
const float peak_sharpening_sigma = (omega < m_peakomega) ? 0.07 : 0.09;
const float peak_sharpening = pow(
m_gamma, exp(-sqrt((omega - m_peakomega) / (peak_sharpening_sigma * m_peakomega)) / 2.0));
return peak_sharpening;
}
/**
* Spectrum-type independent modifications.
*/
static float ocean_spectrum_wind_and_damp(const Ocean *oc,
const float kx,
const float kz,
const float val)
{
const float k2 = kx * kx + kz * kz;
const float k_mag_inv = 1.0f / k2;
const float k_dot_w = (kx * k_mag_inv * oc->_wx) + (kz * k_mag_inv * oc->_wz);
/* Bias towards wind dir. */
float newval = val * pow(fabs(k_dot_w), oc->_wind_alignment);
/* Eliminate wavelengths smaller than cutoff. */
// val *= exp(-k2 * m_cutoff);
/* Reduce reflected waves. */
if (k_dot_w < 0.0f) {
if (oc->_wind_alignment > 0.0) {
newval *= oc->_damp_reflections;
}
}
return newval;
}
static float jonswap(const Ocean *oc, const float k2)
{
/* Get our basic JONSWAP value from #alpha_beta_spectrum. */
const float k_mag = sqrt(k2);
const float m_omega = GRAVITY * k_mag * tanh(k_mag * oc->_depth);
const float omega = sqrt(m_omega);
const float m_fetch = oc->_fetch_jonswap;
/* Strictly, this should be a random value from a Gaussian (mean 3.3, variance 0.67),
* clamped 1.0 to 6.0. */
float m_gamma = oc->_sharpen_peak_jonswap;
if (m_gamma < 1.0) {
m_gamma = 1.00;
}
if (m_gamma > 6.0) {
m_gamma = 6.0;
}
const float m_windspeed = oc->_V;
const float m_dimensionlessFetch = fabs(GRAVITY * m_fetch / sqrt(m_windspeed));
const float m_alpha = 0.076 * pow(m_dimensionlessFetch, -0.22);
const float m_tau = M_PI * 2;
const float m_peakomega = m_tau * 3.5 * fabs(GRAVITY / oc->_V) *
pow(m_dimensionlessFetch, -0.33);
const float beta = 1.25f;
float val = alpha_beta_spectrum(m_alpha, beta, GRAVITY, omega, m_peakomega);
/* Peak sharpening. */
val *= peak_sharpen(m_omega, m_peakomega, m_gamma);
return val;
}
float BLI_ocean_spectrum_piersonmoskowitz(const Ocean *oc, const float kx, const float kz)
{
const float k2 = kx * kx + kz * kz;
if (k2 == 0.0f) {
/* No DC component. */
return 0.0f;
}
/* Get Pierson-Moskowitz value from #alpha_beta_spectrum. */
const float peak_omega_PM = 0.87f * GRAVITY / oc->_V;
const float k_mag = sqrt(k2);
const float m_omega = GRAVITY * k_mag * tanh(k_mag * oc->_depth);
const float omega = sqrt(m_omega);
const float alpha = 0.0081f;
const float beta = 1.291f;
float val = alpha_beta_spectrum(alpha, beta, GRAVITY, omega, peak_omega_PM);
val = ocean_spectrum_wind_and_damp(oc, kx, kz, val);
return val;
}
float BLI_ocean_spectrum_texelmarsenarsloe(const Ocean *oc, const float kx, const float kz)
{
const float k2 = kx * kx + kz * kz;
if (k2 == 0.0f) {
/* No DC component. */
return 0.0f;
}
float val = jonswap(oc, k2);
val = ocean_spectrum_wind_and_damp(oc, kx, kz, val);
/* TMA modifications to JONSWAP. */
const float m_depth = oc->_depth;
const float gain = sqrt(m_depth / GRAVITY);
const float k_mag = sqrt(k2);
const float m_omega = GRAVITY * k_mag * tanh(k_mag * oc->_depth);
const float omega = sqrt(m_omega);
const float kitaigorodskiiDepth_wh = omega * gain;
const float kitaigorodskiiDepth = 0.5 + (0.5 * tanh(1.8 * (kitaigorodskiiDepth_wh - 1.125)));
val *= kitaigorodskiiDepth;
val = ocean_spectrum_wind_and_damp(oc, kx, kz, val);
return val;
}
float BLI_ocean_spectrum_jonswap(const Ocean *oc, const float kx, const float kz)
{
const float k2 = kx * kx + kz * kz;
if (k2 == 0.0f) {
/* No DC component. */
return 0.0f;
}
float val = jonswap(oc, k2);
val = ocean_spectrum_wind_and_damp(oc, kx, kz, val);
return val;
}
/** \} */
#endif /* WITH_OCEANSIM */
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