Opengl/Glut keyboard input trouble - opengl

Question

i have an assignment to draw a pyramid onto the screen and then rotate after i press the 'k' key in my keyboard.
Everything works ok, except the rotation part as the program doesn't seem to be noting me pressing the key. The code goes as follows:
void changeSize(int w, int h) {
if(h == 0)
h = 1;
float ratio = w * 1.0 / h;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, w, h);
// Set perspective
gluPerspective(45.0f ,ratio, 1.0f ,1000.0f);
// return to the model view matrix mode
glMatrixMode(GL_MODELVIEW);
}
void renderScene(void) {
// clear buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// set the camera
glLoadIdentity();
gluLookAt(5.0,5.0,5.0,
0.0,0.0,0.0,
0.0f,2.0f,0.0f);
// put the geometric transformations here
// put drawing instructions here
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
glBegin(GL_LINES);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(-100.0f, 0.0f, 0.0f);
glVertex3f( 100.0f, 0.0f, 0.0f);
glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f(0.0f, -100.0f, 0.0f);
glVertex3f(0.0f, 100.0f, 0.0f);
glColor3f(0.0f, 0.0f, 1.0f);
glVertex3f(0.0f, 0.0f, -100.0f);
glVertex3f(0.0f, 0.0f, 100.0f);
glEnd();
//triangulos da base
glBegin(GL_TRIANGLES);
glColor3f(255.0f,255.0f,255.0f);
glVertex3f(1.0f,0.0f,1.0f);
glVertex3f(-1.0f,0.0f,-1.0f);
glVertex3f(-1.0f,0.0f,1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,1.0f);
glVertex3f(1.0f,0.0f,-1.0f);
glVertex3f(-1.0f,0.0f,-1.0f);
glEnd();
//triangulos das faces
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(-1.0f,0.0f,1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,-1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(1.0f,0.0f,1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,-1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(-1.0f,0.0f,-1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(-1.0f,0.0f,-1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(-1.0f,0.0f,1.0f);
glEnd();
// End of frame
glutSwapBuffers();
}
// write function to process keyboard events
void rotate (unsigned char key, int x, int y) {
if (key == 'k')
glRotatef(45,1.0,1.0,0.0);
glutPostRedisplay();
}
int main(int argc, char **argv) {
// init GLUT and the window
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DEPTH|GLUT_DOUBLE|GLUT_RGBA);
glutInitWindowPosition(100,100);
glutInitWindowSize(1200,1200);
glutCreateWindow("CG#DI-UM");
// Required callback registry
glutDisplayFunc(renderScene);
glutReshapeFunc(changeSize);
// put here the registration of the keyboard callbacks
glutKeyboardFunc(rotate);
// OpenGL settings
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
// enter GLUT's main cycle
glutMainLoop();
return 0;
}
It seems that my program is not noting me pressing the key even tho i am. Im tried only printing the keys that are being pressed, and that works, so i'm really lost here.

Answer 1

glRotatef seem to have no effect in rotate, because glLoadIdentity() is called at the begin of renderScene. Actually glRotatef changes the current matrix, but when the scene is rendered (renderScene), then glLoadIdentity() loads the Identity matrix to the current matrix.
Anyway it is a bad style to do changes to the current matrix in input event callbacks. Change states and values of variables in the input events and use the variables to set the current model view matrix before the scene is rendered in renderScene.
Add a global variable angle:
float angle = 0.0f;
Change the value of the variable in renderScene. e.g:
void rotate (unsigned char key, int x, int y) {
if (key == 'k') {
angle += 45.0f;
glutPostRedisplay();
}
}
And apply the rotation to the current matrix in renderScene:
void renderScene(void) {
// clear buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// set the camera
glLoadIdentity();
gluLookAt(5.0,5.0,5.0,
0.0,0.0,0.0,
0.0f,2.0f,0.0f);
// apply rotation
glRotatef(angle, 1.0f, 1.0f, 0.0f);
// [...]
}