[away3d] plane object vanishes

[andrew barry]

Hi,

Bit confused about the plane object which i used for terrain.
I create like so and it displays along the z-axis in front of me . Now
I have a camera and when i move forward only a little  the plane seems
to disappear. I move back and it re-appears?

Also what y value should this be as y=-100 and y=-50 looks the same?

        // create a plane
                        plane = new Plane({material:"green#", name:"plane", 
y:-100,x:0,
width:1000, height:1000, pushback:true});
                        view.scene.addChild(plane);