The 3D view is rendered generally with OpenGL, and more rarely with DirectX, through Java 3D library. The DirectX switch is done with the properties set in this file.
I don't know if Java 3D will support easily stereo viewing, but if you want to try with Sweet Home 3D code, you should start by Component3DManager class where all Canvas3D instances are created. The layout of the 3D view is done in the HomePane class.