Open GL Rotation - c++

Question

i'm trying to draw 100 arrows in a grid and trying to rotate each arrow according to the size of the input i read. But here when i try to rotate one arrow, all the arrows rotate at once with it. whats wrong with it ?
void drawArrow(void) {
float y1 = 2.0;
float y2 = 2.15;
float y3 = 2.4;
int count2 = 0;
for (float col = 0; col < 10; col++) {
y1 -= 0.5;
y2 -= 0.5;
y3 -= 0.5;
float x1 = -2.25;
float x2 = -2.20;
float x3 = -2.15;
float x4 = -2.35;
float x5 = -2.30;
for (float rows = 0; rows < 10; rows++) {
glPushMatrix();
glTranslatef(-0.35 + 0.5 - 0.1, 0.4 - 0.01 + 0.1, 0.0);
float m = (windx[count2] * windx[count2]) + (windy[count2] * windy[count2]);
float rotator = sqrt(m);
glRotatef(rotator-50, 0.0, 0.0, 1.0);
glBegin(GL_LINE_STRIP);//start drawing a line loop
glColor3f(1.0, 0.0, 0.0);
glVertex3f(x1, y1, 0.0f);
glVertex3f(x2, y2, 0.0f);
glVertex3f(x3, y2, 0.0f); // drawing a arrow
glVertex3f(x1, y3, 0.0f);
glVertex3f(x4, y2, 0.0f);
glVertex3f(x5, y2, 0.0f);
glVertex3f(x1, y1, 0.0f);
x1 += .5;
x2 += .5;
x3 += .5;
x4 += .5;
x5 += .5;
count2 ++;
glEnd();//end drawing of line loop
glPopMatrix();
}
}
int main(int argc, char **argv) {
glMatrixMode(GL_PROJECTION);
glutInit(&argc, argv); // Initialize GLUT
glutInitDisplayMode(GLUT_SINGLE); // Set up a basic display buffer (only single buffered for now)
glutInitWindowSize(1000, 800); // Set the width and height of the window
glutInitWindowPosition(100, 100); // Set the position of the window
glutCreateWindow("Weather Analysis"); // Set the title for the window
readDataFile(); //Read Data From File
glutKeyboardFunc(keyboard);
glutDisplayFunc(display); // Tell GLUT to use the method "display" for rendering
glutReshapeFunc(reshape); // Tell GLUT to use the method "reshape" for reshaping
glutMainLoop(); // Enter GLUT's main loop
void reshape(int width, int height) {
glViewport(0, 0, (GLsizei)width, (GLsizei)height); // Set our viewport to the size of our window
glMatrixMode(GL_PROJECTION); // Switch to the projection matrix so that we can manipulate how our scene is viewed
glLoadIdentity(); // Reset the projection matrix to the identity matrix so that we don't get any artifacts (cleaning up)
gluPerspective(60, (GLfloat)width / (GLfloat)height, 1.0, 100.0); // Set the Field of view angle (in degrees), the aspect ratio of our window, and the new and far planes
glMatrixMode(GL_MODELVIEW); // Switch back to the model view matrix, so that we can start drawing shapes correctly
}
void display(void) {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Clear the background of our window to red
glClear(GL_COLOR_BUFFER_BIT); //Clear the colour buffer (more buffers later on)
glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations
glTranslatef(0.0f, 0.5f, -6.0f);
renderPrimitive(); // Render the primitive
drawArrow();
glFlush(); // Flush
}
and ALSO i dont know what to enter in the GLtranslatef method. Im really a beginner, sorry.

Answer 1

Try to draw your arrow in one rutine lets call it DrawArrow I suggest it size must be between [-1.0f; 1.0f] than place it at the proper position using affine transform first of all translation secondly rotation.
void DrawArrow(void)
{
float x1 = 0;
float x2 = -0.05;
float x3 = -0.1;
float x4 = 0.1;
float x5 = 0.05;
float y1 = -0.15;
float y2 = 0;
float y3 = 0.15;
glBegin(GL_LINE_STRIP);//start drawing a line loop
glColor3f(1.0, 0.0, 0.0);
glVertex3f(x1, y1, 0.0f);
glVertex3f(x2, y2, 0.0f);
glVertex3f(x3, y2, 0.0f); // drawing a arrow
glVertex3f(x1, y3, 0.0f);
glVertex3f(x4, y2, 0.0f);
glVertex3f(x5, y2, 0.0f);
glVertex3f(x1, y1, 0.0f);
glEnd();//
}
Than your array drawing function like this (you may correct inacurrances):
void drawArrows(void) {
float y1 = 2.0;
int count2 = 0;
for (float col = 0; col < 10; col++) {
y1 -= 0.5;
float x1 = -2.25;
for (float rows = 0; rows < 10; rows++) {
glPushMatrix();
glTranslatef(x1, y1, 0.0);
float m = (windx[count2] * windx[count2]) + (windy[count2] * windy[count2]);
float rotator = sqrt(m);
glRotatef(rotator-50, 0.0, 0.0, 1.0);
DrawArrow();
x1 += .5;
count2 ++;
glPopMatrix();
}
}
}
I have made some tests the result will be like this (with constant rotator).