Make fire float up - c++

Question

// this is the display function it is called when ever you want to draw something all drawing should be called form here
void display() {
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// draw background
drawBackground();
glPushMatrix();
// draw hot air balloon
drawAirBalloon();
// draw spray
drawSpray();
glPopMatrix();
// draw rain
drawRain();
// draw fire
drawSpray();
calcFPS();
counter++;
glFlush();
glutSwapBuffers();
glutPostRedisplay();
}
The problem is that I can't make the fire go up with my hot air balloon. The reason why I only put the code above (display) is because I think the problem is to do with this particular code.
To see the full code, click on the link below:
hot air balloon code
This is the problem:

Answer 1

This is because you set the model view matrix to the identity matrix in the function circle.
Replace glLoadIdentity by glPushMatrix()/glPopMatrix() in the function circle():
void circle(double radius, double xc, double yc) {
int i;
double angle = 2 * 3.1415 / 20; // circle is drawn using 20 line.
double circle_xy[100][40];
circle_xy[0][0] = radius + xc;
circle_xy[0][1] = yc;
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
// set fire position
glTranslatef(-40.0, 60.0, 0.0);
glBegin(GL_POLYGON);
for (i = 1; i < 20; i++) {
circle_xy[i][0] = radius * cos(i * angle) + xc;
circle_xy[i][1] = radius * sin(i * angle) + yc;
glVertex2f(circle_xy[i - 1][0], circle_xy[i - 1][1]);
glVertex2f(circle_xy[i][0], circle_xy[i][1]);
}
glEnd();
glPopMatrix();
}
To make the code more comprehensible, I recommend to remove glTranslatef for drawAirBalloon, but to do it in display:
void drawAirBalloon(void) {
// glTranslatef(squareX, squareY, squareZ); <--- remove
// ....
}
void display() {
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// draw background
drawBackground();
glPushMatrix();
glTranslatef(squareX, squareY, squareZ); // <--- insert
// draw spray
drawSpray();
// draw hot air balloon
drawAirBalloon();
glPopMatrix();
// draw rain
drawRain();
calcFPS();
counter++;
glFlush();
glutSwapBuffers();
glutPostRedisplay();
}
You do a lot of effort and you write a lot of tricky and well structured code. I relay recommend, to read about Vertex Specification and Shader. Go on, but start to get rid of the deprecated fixed function pipeline and switch to a moder way of rendering.