Adding gluPerspective and gluLookAt made my drawing disappear - c++

Question

I'm currently working on a basic GUI that create and draw a robot in a 3d space, I'm using OpenGL and freeglut to deal with the 3d part.
Until last week, I was ignoring all the perspective stuff like 'gluLookAt' or 'gluPerspective' ...
Now, I would like to add those things in order to get basic camera movement (rotation, zoom, translation) with user input.
But i'm stuck cause whenever I try to add the perspective part to my code, I'm not able to get my beautiful robot anymore.
here's my current code :
void drawScene(void) {
glClearColor(1.0f,1.0f,1.0f,0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glMatrixMode(GL_MODELVIEW);
glColor3f(0.0f, 0.0f, 0.0f);
ortho();
robot.draw(); // only sone basic lines and quads
glLoadIdentity();
sprintf(title, "robot creation link:%i/joint:%i", robot.linkNumber, robot.jointNumber);
glutSetWindowTitle(title);
glFlush();
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA|GLUT_SINGLE|GLUT_MULTISAMPLE);
glutInitWindowPosition(0,0);
glutInitWindowSize(1360,768);
glEnable(GL_MULTISAMPLE_ARB | GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
id = glutCreateWindow("robot creation");
glutDisplayFunc (drawScene);
glutKeyboardFunc(keyboardHandler);
glutSpecialFunc (specialKeyHandler);
glutMouseFunc (mouseHandler);
glutReshapeFunc (reshapeHandler);
glutMainLoop();
return 0;
}
I wonder if my code need to be completly re-done to work properly with such things or if I'm not using them properly.
Atm I've tried to add this after the window creation :
glViewport(0, 0, 1360, 768);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(180.0f,1360.0f/768.0f,0.1f,1000.0f);
and this in the drawScene function after the drawing part :
gluLookAt(
10.0f, 0.0f, 0.0f,
0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f
);
I know I'm facing the object because I can see a dot in the center of the screen that came from the robot.

Answer 1

You have both matrix modes (model view and projection. It is better to activate one. For gmu perspective try something like gluPerspective(170, 1.33, 0.00001, 1000); or put the camera closer to check if you can see a difference in the object. If you are not able to see the object your matrices are overwriting each other. You can check their values by:Gl.glGetDoublev(Gl.GL_MODELVIEW_MATRIX, modelMatrix);
Gl.glGetDoublev(Gl.GL_PROJECTION_MATRIX, projMatrix);.
Another option is also gluunproject which is easier to work than look at function (in my opinion)