grafika_komputerowa/grk/project/ParticleSystem.h

#pragma once
#include "glew.h"
#include <GLFW/glfw3.h>
#include "glm.hpp"
#include <list>
#include "ext.hpp"


struct Particle
{
public:
	float birthTime;
	glm::vec3 startPosition;
	glm::vec3 direction;
    glm::vec3 randomPointOnCircle;

	float getAge(float time) {
		return time - birthTime;
	}
};

class ParticleSystem
{
private:
    std::list<Particle> particles;
    GLuint VBO;
    GLuint VAO;
    GLfloat vertices[9];
    float lastGenerated = -1.f;

    bool shouldGenerateNewParticle(float time) {
        return lastGenerated == -1.f || time - lastGenerated > generationInterval;
    }

    glm::vec3 generateRandomPointOnCircle() {
        float distanceFromCenter = static_cast <float> (rand()) / static_cast <float> (RAND_MAX/sourceRadius);
        float radians = static_cast <float> (rand()) / static_cast <float> (RAND_MAX / 6.28f);

        glm::vec3 referenceVector(0.0f, 1.0f, 0.0f);
        glm::vec3 output = glm::normalize(glm::cross(sourceDirection, referenceVector)) * distanceFromCenter;

        glm::mat4 rotationMatrix = glm::rotate(glm::mat4(1.0f), radians, sourceDirection);
        output = glm::vec3(rotationMatrix * glm::vec4(output, 1.0f));

        return output;
    }

    void generateNewParticle(float time) {
        Particle newParticle;
        newParticle.birthTime = time;
        newParticle.startPosition = sourcePosition;
        newParticle.randomPointOnCircle = generateRandomPointOnCircle();
        newParticle.direction = sourceDirection;
        particles.push_back(newParticle);
        lastGenerated = time;
    }

    void deleteOld(float time) {
        auto it = particles.begin();

        while (it != particles.end()) {
            if ((*it).getAge(time) > lifetime) {
                it = particles.erase(it);
            }
            else {
                ++it;
            }
        }
    }

    glm::vec3 calculateParticleColor(float age) {
        float rate = glm::clamp(age / lifetime, 0.f, 1.f);
        glm::vec3 mixedColor = (1.0f - rate) * startColor + rate * endColor;
        return mixedColor;
    }

public:
    glm::vec3 sourcePosition;
    float sourceRadius = 0.02f;
    glm::vec3 sourceDirection = glm::vec3(1.f, 0.f, 0.f);
    float generationInterval = 0.0025f;
    float lifetime = 0.5f;
    float speed = 100.f;
    glm::vec3 startColor = glm::vec3(1.f, 0.f, 0.f);
    glm::vec3 endColor = glm::vec3(1.f, 1.f, 0.f);

    ParticleSystem() {
        // Inicjalizacja wierzcho<68>k<EFBFBD>w tr<74>jk<6A>ta w 3D
        vertices[0] = -0.5f; vertices[1] = -0.5f; vertices[2] = 0.0f;
        vertices[3] = 0.5f; vertices[4] = -0.5f; vertices[5] = 0.0f;
        vertices[6] = 0.0f; vertices[7] = 0.5f; vertices[8] = 0.0f;

        glGenBuffers(1, &VBO);
        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

        glGenVertexArrays(1, &VAO);
        glBindVertexArray(VAO);

        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (void*)0);
        glEnableVertexAttribArray(0);

        glBindVertexArray(0);
    }

    void drawParticles(GLuint program, glm::mat4 view, glm::mat4 projection, float time) {
        if (shouldGenerateNewParticle(time)) {
            generateNewParticle(time);
        }

        deleteOld(time);

        glUseProgram(program);
        GLuint modelLoc = glGetUniformLocation(program, "model");
        GLuint viewLoc = glGetUniformLocation(program, "view");
        GLuint projectionLoc = glGetUniformLocation(program, "projection");
        GLuint colorLoc = glGetUniformLocation(program, "color");

        int i = 0;
        for (auto particle : particles) {
            glm::vec3 color = calculateParticleColor(particle.getAge(time));
            glUniform3f(colorLoc, color.x, color.y, color.z);
            glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));
            glUniformMatrix4fv(projectionLoc, 1, GL_FALSE, glm::value_ptr(projection));

            glm::mat4 model = glm::translate(glm::mat4(1.0f), sourcePosition + particle.randomPointOnCircle);
            model = glm::scale(model, glm::vec3(0.005f, 0.005f, 0.005f));
            model = glm::translate(model, particle.direction * speed * (time - particle.birthTime));
            glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));

            glBindVertexArray(VAO);
            glDrawArrays(GL_TRIANGLES, 0, 3);
            i++;
        }
        
        glBindVertexArray(0);
    }
};