ParticleSystem.cpp

#include "ParticleSystem.h"
#include "Window.h"


ParticleSystem::ParticleSystem()
{
	init();
}

ParticleSystem::~ParticleSystem()
{
}

void ParticleSystem::init()
{
	GLfloat particle_quad[] = {
		0.0f, 1.0f, 0.0f, 1.0f,
		1.0f, 0.0f, 1.0f, 0.0f,
		0.0f, 0.0f, 0.0f, 0.0f,

		0.0f, 1.0f, 0.0f, 1.0f,
		1.0f, 1.0f, 1.0f, 1.0f,
		1.0f, 0.0f, 1.0f, 0.0f
	};

	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glBindVertexArray(VAO);
	// Fill mesh buffer
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(particle_quad), particle_quad, GL_STATIC_DRAW);
	// Set mesh attributes
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)0);
	glBindVertexArray(0);

	// Create this->amount default particle instances
	for (GLuint i = 0; i < max; ++i) {
		particles.push_back(Particle());
	}
}

void ParticleSystem::draw(GLuint shader)
{
	glUseProgram(shader);
	for (Particle particle : this->particles)
	{
		if (particle.Life > 0.0f)
		{
			//this->shader.SetVector2f("offset", particle.Position);
			//this->shader.SetVector4f("color", particle.Color);
			//this->texture.Bind();

			glBindVertexArray(this->VAO);
			glDrawArrays(GL_TRIANGLES, 0, 6);
			glBindVertexArray(0);
		}
	}
	// Don't forget to reset to default blending mode
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}

void ParticleSystem::update()
{

}
GLuint lastUsedParticle = 0;
GLuint ParticleSystem::firstUnusedParticle()
{
	// First search from last used particle, this will usually return almost instantly
	for (GLuint i = lastUsedParticle; i < max; ++i) {
		if (this->particles[i].Life <= 0.0f) {
			lastUsedParticle = i;
			return i;
		}
	}
	// Otherwise, do a linear search
	for (GLuint i = 0; i < lastUsedParticle; ++i) {
		if (this->particles[i].Life <= 0.0f) {
			lastUsedParticle = i;
			return i;
		}
	}
	// All particles are taken, override the first one (note that if it repeatedly hits this case, more particles should be reserved)
	lastUsedParticle = 0;
	return 0;
}

void ParticleSystem::respawnParticle(Particle & particle, glm::vec3 position, glm::vec3 velocity, glm::vec3 offset)
{
	GLfloat random = ((rand() % 100) - 50) / 10.0f;
    GLfloat rColor = 0.5 + ((rand() % 100) / 100.0f);
    particle.Position = position + random + offset;
    particle.Color = glm::vec4(rColor, rColor, rColor, 1.0f);
    particle.Life = 1.0f;
    particle.Velocity = velocity * 0.1f;
}