particle.h
// Copyright 2016 Olivier Gillet.
//
// Author: Olivier Gillet (ol.gillet@gmail.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// 
// See http://creativecommons.org/licenses/MIT/ for more information.
//
// -----------------------------------------------------------------------------
//
// Random impulse train processed by a resonant filter.

#ifndef PLAITS_DSP_NOISE_PARTICLE_H_
#define PLAITS_DSP_NOISE_PARTICLE_H_

#include "stmlib/dsp/dsp.h"
#include "stmlib/dsp/filter.h"
#include "stmlib/utils/random.h"

namespace plaits {

class Particle {
 public:
  Particle() { }
  ~Particle() { }

  inline void Init() {
    pre_gain_ = 0.0f;
    filter_.Init();
  }
  
  inline void Render(
      bool sync,
      float density,
      float gain,
      float frequency,
      float spread,
      float q,
      float* out,
      float* aux,
      size_t size) {
    float u = stmlib::Random::GetFloat();
    if (sync) {
      u = density;
    }
    bool can_radomize_frequency = true;
    while (size--) {
      float s = 0.0f;
      if (u <= density) {
        s = u * gain;
        if (can_radomize_frequency) {
          const float u = 2.0f * stmlib::Random::GetFloat() - 1.0f;
          const float f = std::min(
              stmlib::SemitonesToRatio(spread * u) * frequency,
              0.25f);
          pre_gain_ = 0.5f / stmlib::Sqrt(q * f * stmlib::Sqrt(density));
          filter_.set_f_q<stmlib::FREQUENCY_DIRTY>(f, q);
          // Keep the cutoff constant for this whole block.
          can_radomize_frequency = false;
        }
      }
      *aux++ += s;
      *out++ += filter_.Process<stmlib::FILTER_MODE_BAND_PASS>(pre_gain_ * s);
      u = stmlib::Random::GetFloat();
    }
  }
 
 private:
  float pre_gain_;
  stmlib::Svf filter_;
  
  DISALLOW_COPY_AND_ASSIGN(Particle);
};

}  // namespace plaits

#endif  // PLAITS_DSP_NOISE_PARTICLE_H_