I am trying to draw sections of triangle fans to form a circle. Each circle sector will have 36 triangles (PIE_SECTION) to make a sector for a pie chart. The colors are randomized in another function (randomPieColor()) but a default color of (0, 0, 0) wouldn’t work as well. Basically, nothing has appeared in the screen with this code. I seem to be able to individually draw a sector by keying in each vertex of a triangle_fan, rather than using a ‘for loop’. However, as stated, its 36 triangles per sector, and the values (zoo1[i].bananas) are randomized as well.. So, its tough manually keying the vertices without a ‘for loop’.

I am not sure what is the problem here, honestly. Here are the codes : 

void plotPie1(){
	GLfloat centerX = 100;
	GLfloat centerY = 150;
	GLfloat startingAngle = 0;
	GLfloat endAngle;
	GLfloat angleIncrement;
	randomPieColor();

	GLfloat radius = 50;
	GLint totalBan = 0;
	for(int i = 0; i < YEARSIZE; i++)
		totalBan += zoo1[i].bananas;

	for(int i = 0; i < YEARSIZE; i++){
		endAngle = zoo1[i].bananas / totalBan * 360.0f;
		drawCircle(zoo1[i].pieColors, centerX, centerY, radius, startingAngle, endAngle);
		startingAngle += endAngle;
	}
}

void drawCircle(Color color, GLfloat x, GLfloat y, GLfloat radius, GLfloat startingAngle, GLfloat endingAngle){
	GLfloat pi = 22 / 7;
	glColor3ub(color.red, color.green, color.blue);
	GLfloat angle = startingAngle * (pi / 180);
	GLfloat angle_increment = endingAngle * (pi / (180 * PIE_SECTION));

	glBegin(GL_TRIANGLE_FAN);
	glVertex2f(x, y);
	
	for(int i = 0; i <= PIE_SECTION; i++){
		glVertex2f(x + radius * cos(angle), y + radius * sin(angle));
		angle += angle_increment;
	}
	glEnd();
}

As you can see, what I am trying to do is to get an angle for a sector, and split it into 36 sectors which is the const PIE_SECTION. With the starting angle, and the ending angle defined to draw the circle in a clockwise fashion starting from the 2nd quadrant at 0 degrees, illustrated below:

At each loop, the angle will be incremented to its total angle, 36 sectors combined. Please help me take a look at the logic, as well as why nothing is shown on my screen with this code..

Thanks!

Update: It looks like my logic to getting the angle is wrong. I have changed it from 

endAngle = zoo1[i].bananas / totalBan * 360.0f;

to

endAngle = 360.0f / totalBan * zoo1[i].bananas;

and it worked!

But I am getting an extra white sector in my chart.. I will continue to scan through the code.