I was recently asked this question: "I don't really see why I want to generate X3D when I can just call OpenGL and write my own code.?" Sure, you can. But to write it efficiently requires lots of acquired knowledge....
Open Standards for Real-Time 3D Communication
A nonprofit organization that develops and maintains the X3D standard--a 3D file format and runtime specification that is open, royalty free and ISO ratified for transmission of 3D data over networks.