Flickering with Particles in OpenGL C++

I am having trouble with this code. I want it to fire fireworks that explode and fall in front of a static background. Right now the fireworks and background work, but together they cause a flickering and the fireworks don't fall at a regular rate. How do I prevent this flickering and achieve a regular rate of firework's fall?

#include <GL/freeglut.h> #include <math.h> #include <stdlib.h> #include <stdio.h> #include <iostream> #include <iomanip> #include "Header.h" using namespace std; #define M_PI (3.1415926535897932384626433832795) GLfloat randomNum() { return (rand() % 10000) / 10000.0; } GLfloat nx = 0; GLfloat ny = .8; #define MAX_POINTS 750 GLfloat numPoints; GLfloat curx, cury; GLfloat x[MAX_POINTS], y[MAX_POINTS]; GLfloat xacc[MAX_POINTS], yacc[MAX_POINTS]; GLfloat red, green, blue; int step; int length; GLfloat newRed = 0; GLfloat newGreen = 0; GLfloat newBlue = 0; GLint totPor = 0; GLint strontiumPor = 0; GLfloat bariumPor = 0; GLfloat copperPor = 0; GLfloat sodiumPor = 0; GLfloat phosPor = 0; GLfloat red2; GLfloat green2; GLfloat green3; GLfloat blue2; void initialize() { int j; double temp, temp2; numPoints = randomNum()*(MAX_POINTS - 1); curx = nx; cury = ny; //Color Mixing if (totPor != 0) { red = newRed * strontiumPor / (totPor - strontiumPor); //s red green = newGreen * bariumPor / (totPor - bariumPor); //b green blue = newBlue * copperPor / (totPor - copperPor); //c blue red2 = newRed * sodiumPor / (totPor - sodiumPor); //d yellow green2 = newGreen * sodiumPor / (totPor - sodiumPor); green3 = newGreen * phosPor / (totPor - phosPor); //p blue green blue2 = newBlue * phosPor / (totPor - phosPor); red = red + red2; green = green + green2 + green3; blue = blue + blue2; } else { red = newRed; green = newGreen; blue = newBlue; } glPointSize(1.7); step = 0; length = 500 + 300 * randomNum(); /* initialize the blast */ for (j = 0; j<numPoints; j++) { x[j] = curx; y[j] = cury; temp = randomNum(); temp2 = randomNum()*2.0*M_PI; xacc[j] = (cos(temp2) * temp) / length; yacc[j] = (sin(temp2) * temp) / length; } } void draw_fireworks(void) { int i; double glow = (length - (step)) / (double)length; glColor3f(red*glow, green*glow, blue*glow); //glow glBegin(GL_POINTS); for (i = 0; i<numPoints; i++) { x[i] += xacc[i]; y[i] += yacc[i]; glVertex2f(x[i], y[i]); } glEnd(); glFlush(); glutSwapBuffers(); } void display(void) { int i; glClear(GL_COLOR_BUFFER_BIT); if (step < 0.9*length) { for (i = 0; i<numPoints; i++) yacc[i] -= 0.02 / length; // gravity draw_fireworks(); } step++; if (step > length) initialize(); DrawScene(); glutSwapBuffers(); } int t = 0; void idle(void) { if (t == 45000) { glutPostRedisplay(); t = 0; } t++; } void SpecialKey(int key, int x, int y) { switch (key) { case GLUT_KEY_LEFT: /* Move fireworks left or right, up or down */ nx = nx + -.025; break; case GLUT_KEY_RIGHT: nx = nx + .025; break; case GLUT_KEY_UP: ny = ny + .025; break; case GLUT_KEY_DOWN: ny = ny + -.025; break; } glutPostRedisplay(); } void Keyboard(unsigned char key, int x, int y) { //Select Chemicals switch (key) { case 's': newRed = 1; strontiumPor = strontiumPor + 1; totPor = totPor + 1; break; case 'b': newGreen = 1; bariumPor = bariumPor + 1; totPor = totPor + 1; break; case 'c': newBlue = 1; copperPor = copperPor + 1; totPor = totPor + 1; break; case 'd': newRed = 1; newGreen = 1; sodiumPor = sodiumPor + 1; totPor = totPor + 1; break; case 'p': newBlue = 1; newGreen = 1; phosPor = phosPor + 1; totPor = totPor + 1; break; case 'R': newRed = newRed + .1; break; case 'G': newGreen = newGreen + .1; break; case 'B': newBlue = newBlue + .1; break; case ' ': //Space bar is Reset or start newRed = 1; newGreen = 1; newBlue = 1; totPor = 0; strontiumPor = 0; bariumPor = 0; copperPor = 0; sodiumPor = 0; phosPor = 0; break; case 'm': nx = 0; ny = 0.8; //M resets target to default break; case 'q': exit(0); //Q is quit } glutPostRedisplay(); } void reshape(int w, int h) { glViewport(0, 0, (GLsizei)w, (GLsizei)h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); if (w <= h) glOrtho(-1.0, 1.0, -1.0*(GLfloat)h / (GLfloat)w, 1.0*(GLfloat)h / (GLfloat)w, -1.0, 1.0); else glOrtho(-1.0*(GLfloat)w / (GLfloat)h, 1.0*(GLfloat)w / (GLfloat)h, -1.0, 1.0, -1.0, 1.0); glMatrixMode(GL_MODELVIEW); } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize(700, 700); glutInitWindowPosition(0, 0); glutCreateWindow("Fireworks Display"); glClearColor(0.0, 0.0, 0.0, 0.0); initialize(); initText(); glutDisplayFunc(display); glutReshapeFunc(reshape); glutIdleFunc(idle); glutKeyboardFunc(Keyboard); glutSpecialFunc(SpecialKey); glutMainLoop(); return 0; } 

And then also this:

#include <GL/freeglut.h> #include "Soil.h" GLuint tex_ID; void LoadTextureMap() { int width, height, channels; unsigned char* image = SOIL_load_image("washington.png", &width, &height, &channels, SOIL_LOAD_AUTO); glGenTextures(1, &tex_ID); glBindTexture(GL_TEXTURE_2D, tex_ID); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexImage2D(GL_TEXTURE_2D, 0, channels, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image); SOIL_free_image_data(image); } void Tree(GLfloat x, GLfloat y, GLfloat z) { glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, tex_ID); glPushMatrix(); glRotatef(180, 0.0f, 0.0f, 1.0f); glColor3f(1.0f, 1.0f, 1.0f); glBegin(GL_QUADS); glTexCoord2f(0.0, 0.0); glVertex3f(-1.0 + x, -1.0 + y, 1.0 + z); glTexCoord2f(0.0, 1.0); glVertex3f(-1.0 + x, 1.0 + y, 1.0 + z); glTexCoord2f(1.0, 1.0); glVertex3f(1 + x, 1.0 + y, 1.0 + z); glTexCoord2f(1.0, 0.0); glVertex3f(1 + x, -1.0 + y, 1.0 + z); glEnd(); glPopMatrix(); glDisable(GL_TEXTURE_2D); } void DrawScene() { Tree(0, 0, 0); } void initText() { LoadTextureMap(); }