While messing around with 3D game engines and digital elevation models I realised that it's pretty simple to transform geographic elevation data stored on raster files into x3d terrain models.
The result was the script: gdal2x3d
The main goal of this code is to read the digital elevation from a tif, hgt or similitar files (read through GDAL) and store the sequence of height levels in an ElevationGrid on a x3d file.
By doing this the 3D model created can be imported on 3D applications such as Blender or game engines such as crystal space.
All the best!