#include <GL/glut.h>



#define MAX_PARTICLES 1000       // 最大粒子数

#define PARTICLE_RADIUS 0.5f     // 粒子半径



static GLfloat pos[MAX_PARTICLES][3];    // 粒子位置

static GLfloat vel[MAX_PARTICLES][3];    // 粒子速度

static GLubyte col[MAX_PARTICLES][4];    // 粒子颜色

void drawScene() {



    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_BLEND);

    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);



    // 画粒子

    glBegin(GL_POINTS);

    for (int i = 0; i < MAX_PARTICLES; i++) {

        glColor4ub(col[i][0], col[i][1], col[i][2], col[i][3]);

        glVertex3f(pos[i][0], pos[i][1], pos[i][2]);

    }

    glEnd();



    // 计算粒子位置和速度

    for (int i = 0; i < MAX_PARTICLES; i++) {

        vel[i][1] += 0.0001f;    // 向上的速度增加

        pos[i][0] += vel[i][0];

        pos[i][1] += vel[i][1];

        pos[i][2] += vel[i][2];

        col[i][3] -= 0.001f;      // 粒子透明度减少

    }

    // 如果透明度小于等于0, 重新随机生成粒子位置、速度和颜色

    for (int i = 0; i < MAX_PARTICLES; i++) {

        if (col[i][3] <= 0) {

            col[i][0] = rand() % 256;

            col[i][1] = rand() % 256;

            col[i][2] = rand() % 256;

            col[i][3] = 255;

            pos[i][0] = 0;

            pos[i][1] = 0;

            pos[i][2] = 0;

            vel[i][0] = ((rand() % 100) - 50) / 500.0f;

            vel[i][1] = ((rand() % 100) - 50) / 500.0f;

            vel[i][2] = ((rand() % 100) - 50) / 500.0f;

        }

    }



    glutSwapBuffers();

}



void init() {

    glClearColor(0.0, 0.0, 0.0, 1.0);

    glMatrixMode(GL_PROJECTION);

    gluPerspective(60, 1, 0.1, 100);

    glMatrixMode(GL_MODELVIEW);

    gluLookAt(0, 5, 20, 0, 0, 0, 0, 1, 0);



    // 初始化粒子位置、速度和颜色

    for (int i = 0; i < MAX_PARTICLES; i++) {

        col[i][0] = rand() % 256;

        col[i][1] = rand() % 256;

        col[i][2] = rand() % 256;

        col[i][3] = 255;

        pos[i][0] = 0;

        pos[i][1] = 0;

        pos[i][2] = 0;

        vel[i][0] = ((rand() % 100) - 50) / 500.0f;

        vel[i][1] = ((rand() % 100) - 50) / 500.0f;

        vel[i][2] = ((rand() % 100) - 50) / 500.0f;

    }

}



int main(int argc, char *argv[]) {

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);

    glutInitWindowSize(600, 600);

    glutCreateWindow("Effect");



    init();

    glutDisplayFunc(drawScene);

    glutIdleFunc(drawScene);

    glutMainLoop();



    return 0;

}