LightWave Basics Tutorial: Animating Surface Transparency Over Time
Check out Liberty3d.com for more cg training videos.
In this mini tutorial, I show how to use an envelope to animate the transparency of a layer over time.
First I set it up in the layer-based surface editor and then I show how to set it up in the Node Editor.
In some cases, it may be faster and easier to simply render the two parts out separately. There are situations where certain things in your scene won't like partially transparent objects, and rendering takes longer when the 3D app has to calculate light traveling through a surface.