3D Camera class not working like it should

Question

Can someone tell me why my camera class isn't working correctly? I set the position vector to (0,0,-10) and the look at vector to (0,0,0) but when I draw something on (0,0,0) it isn't there. I'm very new to vector math and matrix stuff, so I'm betting it's LookThrough() where the problem is.

import org.lwjgl.opengl.GL11;
import org.lwjgl.util.vector.Matrix3f;
import org.lwjgl.util.vector.Vector3f;

public class Camera {
     //3d vector to store the camera's position in
    Vector3f position = null;
    Vector3f lookAt = null;
    //the rotation around the Y axis of the camera
    float yaw = 0;

    //the rotation around the X axis of the camera
    float pitch = 0;

    //the rotation around the Z axis of the camera
    float roll = 0;

    public Camera(float x, float y, float z)
    {
        //instantiate position Vector3f to the x y z params.
        position = new Vector3f(x, y, z);
        lookAt = new Vector3f();
    }

    public void lookThrough()
    {
        Matrix3f m = new Matrix3f();



        Vector3f out = new Vector3f();
        Vector3f.sub(position, lookAt, out);
        out.normalise();
        //set forward vector
        m.m00 = out.x;
        m.m01 = out.y;
        m.m02 = out.z;

        //set right vector
        m.m10 = 1;
        m.m11 = 0;
        m.m12 = 0;

        //set up vector
        m.m20 = 0;
        m.m21 = 1;
        m.m22 = 0;

        yaw = (float) -(Math.tan(m.m10/m.m00));
        pitch = (float) -(Math.tan((-m.m20)/(Math.sqrt(Math.pow(m.m21, 2) + Math.pow(m.m22, 2)))));
        roll = (float) -(Math.tan(m.m21/m.m22));

        //roatate the pitch around the X axis
        GL11.glRotatef(pitch, 1.0f, 0.0f, 0.0f);
        //roatate the yaw around the Y axis
        GL11.glRotatef(yaw, 0.0f, 1.0f, 0.0f);
        //roatate the yaw around the Y axis
        GL11.glRotatef(roll, 0.0f, 0.0f, 1.0f);
        //translate to the position vector's location
        GL11.glTranslatef(position.x, position.y, position.z);
    }
}

Answer 1

There are a couple of things about your class that I would highlight:

1) You are fixing your 'right' and 'up' vectors, leaving only one degree of rotational freedom. As the camera re-orients in 3D space these will need to change. As it stands, your calculation for pitch always evaluates to 0, while your calculation to roll always evaluates to tan(1/0).

2) Though I'm not familiar with Java, you appear to be using the calculation (position - lookAt) to derive your forward vector. Ought it not be the reverse? The forward vector points away from the viewer's position.

3) Again - not familiar with java - but calling pow() to do a single multiplication is likely overkill.

1 & 2 could be the cause of your woes. Ultimately I would suggest taking a look at gluLookAt - assuming the GLU library is available in Java. If it is not, then look at the source code for gluLookAt (one variant is available here ).