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#include "particlesystem.h"
#include <iostream>
particlesystem::particlesystem()
{
}
std::pair<double,double> sample_complex_gaussian(){
double uniform_1 = (double)rand() / (RAND_MAX);
double uniform_2 = (double)rand() / (RAND_MAX);
// set a lower bound on zero to avoid undefined log(0)
if (uniform_1 == 0)
{
uniform_1 = 1e-10;
}
if (uniform_2 == 0)
{
uniform_2 = 1e-10;
}
// real and imaginary parts of the complex number
double real = sqrt(-2*log(uniform_1)) * cos(2*M_PI*uniform_2);
double imag = sqrt(-2*log(uniform_1)) * sin(2*M_PI*uniform_2);
return std::make_pair(real, imag);
}
float getRandomInRange(float max, float min){
return min + static_cast <float> (rand()) /( static_cast <float> (RAND_MAX/(max-min)));
}
float getRandomY(){
return getRandomInRange(.001,.2);
}
Eigen::Vector3f particlesystem::getRandomInitialVel(){
std::pair<float, float> r = sample_complex_gaussian();
return factor*Eigen::Vector3f(r.first, getRandomY(), r.second);
}
Eigen::Vector3f getInitVel(OceanSpray s){
float x = getRandomInRange(.6,4);
float y = getRandomInRange(0.5, 1.5);
Eigen::Vector3f v = Eigen::Vector3f(s.slope_vector[0], y, s.slope_vector[1]) + Eigen::Vector3f(x,0,0);
return v*300.f;
//p.vel[1] = 0.1;
}
void particlesystem::init(std::vector<OceanSpray> verts){
// make sure to set m_verts
setVerts(verts);
m_particles.reserve(4000);
for (auto v : m_verts){
Particle p;
p.pos = Eigen::Vector3f(v.height);
p.life = getRandomInRange(.6,1);
// p.vel = v.slope*factor;
//p.vel = getRandomInitialVel();
p.vel = getInitVel(v);
m_particles.push_back(p);
}
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, m_vertices.size()*sizeof(float), m_vertices.data(), GL_STATIC_DRAW);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4*sizeof(float), (void*)0);
// unbind
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
void particlesystem::update(double deltaTime){
// add new particles
for (int i=0; i<m_particles.size(); i++){
int particle_index = getUnusedParticleIndex();
if (particle_index == -1) continue;
if (particle_index >= m_particles.size() - 1 || particle_index >= m_verts.size() - 1) continue;
respawn_particle(m_particles[particle_index], m_verts[particle_index]);
}
float dt = deltaTime;
// update all particles values
for (Particle &p : m_particles){
p.life -= deltaTime * getRandomInRange(.1f, .9f);
// if particle is still alive, update pos
if (p.life >= 0.f){
float r = getRandomInRange(30, 80.f);
p.vel += gravity*dt*r;
p.pos += p.vel * dt;
// p.vel[1] -= (p.vel.dot(p.vel) / 2 + gravity[0]) * dt;
// p.pos += p.vel * dt * 10.f;
}
if (p.pos[1] < 0.f) p.life = 0.f;
}
}
// finds the first instance of a particle that is dead, and returns its index so it can be replaced
int particlesystem::getUnusedParticleIndex(){
// search from last used index
for (int i=lastUsedIndex; i<m_verts.size(); ++i){
if (m_particles[i].life <= 0.f){
lastUsedIndex = i;
return i;
}
}
// otherwise do linear search up to last used
for (int i=0; i<lastUsedIndex; ++i){
if (m_particles[i].life <= 0.f){
lastUsedIndex = i;
return i;
}
}
// if no dead ones found, don't respawn
lastUsedIndex = 0;
//std::cout << "first particle override!" << std::endl;
return -1;
}
void particlesystem::respawn_particle(Particle &p, OceanSpray s){
p.pos = Eigen::Vector3f(s.height);
p.vel = getInitVel(s);
// reset life
p.life = 1.f;
}
void particlesystem::draw(Shader *shader, Camera m_camera, GLuint texture){
shader->bind();
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
// activate texture
glActiveTexture(GL_TEXTURE10);
glBindTexture(GL_TEXTURE_2D, texture);
glUniform1i(glGetUniformLocation(shader->id(), "particle_texture"), 10);
// manually set view and projection, for non-translating view
Eigen::Matrix4f projection = m_camera.getProjection();
Eigen::Matrix4f view = m_camera.getView();
// view.col(3) = Eigen::Vector4f(0, 0, 0, 0);
glUniformMatrix4fv(glGetUniformLocation(shader->id(), "view"), 1, GL_FALSE, view.data());
glUniformMatrix4fv(glGetUniformLocation(shader->id(), "projection"), 1, GL_FALSE, projection.data());
// shader->setUniform("model", model);
int i = 0;
for (Particle p : m_particles){
if (p.life >= 0.f){
shader->setUniform("offset", p.pos);
shader->setUniform("alpha", p.life);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, m_vertices.size());
glBindVertexArray(0);
i++;
}
}
shader->unbind();
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}
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