Билборд в LWJGL

Опитвах се да направя билборд с помощта на LWJGL и успях частично. Четворката се появява и се изправя пред камерата, когато се нахвърлям. Въпреки това, веднага щом завъртя камерата по някоя от осите, четворката също се движи по осите по различни начини. Ето кода, който използвам:

/***************************************************************************************************************************************************************************************************
 * All rendering happens here...
 **************************************************************************************************************************************************************************************************/
private void render() {

    GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
    GL11.glLoadIdentity(); // Reset The View

    //GL11.glLight(GL11.GL_LIGHT1, GL11.GL_POSITION, lightPosition); // Position The Light

    GL11.glRotatef(360.0f - yrot, 0, 1.0f, 0);
    GL11.glRotatef(lookupdown, 1.0f, 0, 0);

    GL11.glTranslatef(-xpos, 0, -zpos);


    GL11.glCallList(blocksList);
    GL11.glCallList(tilesList);
    GL11.glCallList(roofList);

    /* Render billboards */
    Billboard bb = lvLoader.currentLevel.billboards[0];
    GL11.glPushMatrix();
    GL11.glRotatef(360.0f - yrot, 0, -1.0f, 0);
    GL11.glRotatef(lookupdown, -1.0f, 0, 0);
    GL11.glBegin(GL11.GL_QUADS);
    GL11.glVertex3f(bb.origin.x + 0.5f, bb.origin.y + 0.5f, bb.origin.z);
    GL11.glVertex3f(bb.origin.x - 0.5f, bb.origin.y + 0.5f, bb.origin.z);
    GL11.glVertex3f(bb.origin.x - 0.5f, bb.origin.y - 0.5f, bb.origin.z);
    GL11.glVertex3f(bb.origin.x + 0.5f, bb.origin.y - 0.5f, bb.origin.z);
    GL11.glEnd();
    GL11.glPopMatrix();

Ето функциите, контролиращи lookupdown и yrot.

if (Keyboard.isKeyDown(Keyboard.KEY_UP)) { // Is PageUp Being Pressed?
        lookupdown -= 1.0f; // Rotate The Secene Downwards
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_DOWN)) { // Is PageDown Being Pressed?
        lookupdown += 1.0f; // Rotate The Scene Upwards
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_RIGHT))
    {
        yrot -= 1.5f; // Rotate The Scene To The Left
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_LEFT))
    {
        yrot += 1.5f; // Rotate The Scene To The Left
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_W))
    {
        adjustXZ((float) Math.sin(yrot * piover180) * 0.05f, (float) Math.cos(yrot * piover180) * 0.05f, false, false);
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_S))
    {
        adjustXZ((float) Math.sin(yrot * piover180) * 0.05f, (float) Math.cos(yrot * piover180) * 0.05f, true, true);
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_D))
    {
        adjustXZ((float) Math.sin((yrot-90) * piover180) * 0.05f, (float) Math.cos((yrot-90) * piover180) * 0.05f, false, false);
    }

    if (Keyboard.isKeyDown(Keyboard.KEY_A))
    {
        adjustXZ((float) Math.sin((yrot+90) * piover180) * 0.05f, (float) Math.cos((yrot+90) * piover180) * 0.05f, false, false);
    }

private void adjustXZ(float x, float z, boolean xAdd, boolean zAdd)
{
    if (collisionCheck(x, z, xAdd, zAdd))
        return;

    if (xAdd)
        xpos += x;
    else if (!xAdd)
        xpos -= x;

    if (zAdd)
        zpos += z;
    else if (!zAdd)
        zpos -= z;
}