i asked this question for you, one man named "Meng" from China.
he known as m17design, if you heard about him.
one of the best guys in VRML.
anyway, for your question he gave me this:
http://www.bitmanagement.de/developer/contact/labs/composite_rgba.html
http://www.bitmanagement.de/developer/contact/labs/composite_rgba.wrl
http://www.bitmanagement.de/developer/contact/relnotes80.html#MTouch
hope its helps.