Android OpenGl moving camera and drawing objects

Question

I'm creating an app, which should draw objects in constant place on the scene, but when i move my phone around, camera should change view and i should see all object around (when i do full rotation with phone).

When i use gl.glMultMatrixf(rotationMatrix, 0) in my onDrawFrame method and then draw object its working perfect (rotation matrix is obtained from SensorManager)

    @Override
    public void onDrawFrame(GL10 gl) {

        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
        gl.glLoadIdentity();

        gl.glMultMatrixf(rotationMatrix, 0);

        gl.glTranslatef(0f, 0f, -10f);
        //draw object
        pyramid.draw(gl);

    }

    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {

        gl.glViewport(0, 0, width, height);
        gl.glMatrixMode(GL10.GL_PROJECTION);
        gl.glLoadIdentity();
        GLU.gluPerspective(gl, 45.0f, (float) width / (float) height, 0.1f, 100.0f);
        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glLoadIdentity();
    }

But when i try to use:

    GLU.gluLookAt( gl, 0.0f, 0.0f, 0.0f, x, y, z, 0.0f, 1.0f, 0.0f ); 
    gl.glPushMatrix();
    //draw object
    pyramid.draw(gl);

my object is all time in the same place on screen and follow camera movement. What I'm doing wrong in second example ?

Your gluLookAt function says you're standing at the origin and looking at (x,y,z), which I'm guessing is coming in from the sensors. If you also want to "walk" around in your world, you'll need to modify the first three parameters of gluLookAt as well to update the eye's position. — radical7

Adam Phelps Adam Phelps · Accepted Answer · 2013-02-02T20:16:36

I think you are unclear on what glulookat() actually does. You are asking for a matrix representing glulookat(currentrotationmatrix, mylocation.x, mylocation.y, mylocation.z, whereImlooking.x, whereImlooking.y, whereImlooking.z, upvector.x, upvector.y, upvector.z)

So with that code you are telling opengl to rotate everything, (assuming that code is still present) and then you are saying "I am at origin (0.0, 0.0, 0.0) and looking at xyz" (not sure what xyz is in your case. or what effect you are trying to achieve.)

Android OpenGl moving camera and drawing objects

1 Answers