Question

I have an OpenGL ES object which I am trying to draw. The object has fairly large vertice values with the x and y co-ordinates lying between -30,000 and +30,000. The z values are between 2000 and -2000.

Can anybody advise me how I should be setting up my viewport ? I am using the following code :

public void onSurfaceChanged(GL10 gl, int width, int height) {
    //Define the view frustrum
    gl.glViewport(0, 0, width, height);
    gl.glMatrixMode(GL10.GL_PROJECTION);
    gl.glLoadIdentity();
    float ratio = (float)width/height;
    GLU.gluPerspective(gl, 45.0f, ratio, 1, 100f);
}

public void onDrawFrame (GL10 gl) {
    // Clear the screen to black.
    gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);

    //Position the model.
    gl.glMatrixMode(GL10.GL_MODELVIEW);
    gl.glLoadIdentity();
    gl.glTranslatef(0.0f, 0.0f, 0.0f);
    //gl.glScalef(0.000015f,0.000015f,0.000015f);

This compiles ok, but I cannot see my object at all.

Thank you.

Answer 1

You probably can’t see it because your camera’s inside the object. Maybe try first scaling it by 0.001 to get it down to about 60 units across, translate it by -50 in the z direction (to get it to the middle of your z range), and see if it shows up then.

Alternatively you could just make your z-range a lot bigger, and translate it by some -50,000 units in the z direction to move the object back from the camera. You’ll have to adjust znear/zfar then to be much larger.