[openvrml-develop] the model with clear glass

[stone <12s...@16...>]

 Hi all!
I'm using ARToolKit with OpenVRML0.14.3 and OpenVRML 0.16.6.
I created a .wrl file of model with clear glass.But in OpenVRML,and the glass is set alpha=0.
It looks like a skylight,I can't see the thing behind the glass in model,but I can see the thing under the model.
What's wrong with this?Who can help me?