Sorry that I don’t know must about how shader and texture work…
http://www.comptricks.com/wp-content/uploads/2012/01/koobit_pdf_view.jpg
I want to render a book model like this. However , the model that I create is just a rectangle (which building from Box in Jmonkey3) that contain the
Texture Image of single page. How can I apply the black shadow to the center of the book ??
For now I can just think of to merge the shadow ( shadow.png) with the Image in Texture, Is there any way to accomplish this in Jmonkey3 ?
Thanks you in Advance 
You can place another quad on top that contains the shadow as the texture. It might just be easier to add the shadow in an image editor however.
Does this need to be rendered this way?
I would think that this kind of thing would be best as a GUI image with GUI text overlay.
Rendering text to a quad/rectangle in 3d is not always going to be legible.
My vote is for using the GUI layer… try Nifty for this.
Nifty is kind of made for exactly this stuff… You could even make a transition effect that turns the pages… Check the documentation: http://freefr.dl.sourceforge.net/project/nifty-gui/nifty-gui/nifty-gui-the-manual-v1.0.pdf
Thanks you every one. I will try what you suggest