I have therefore gone through the current X3D spec and produced a list of changes in order to add double-precision support to all appropriate sections. Presumedly a simple search and replace can update this at a later stage when naming conventions are resolved. New fields added are SFDouble, MFDouble, SFVec3d, and MFVec3d. Attached is an HTML document with all changes listed. Comments are in red.
Text is in black.
Let me know if there are any problems with this. The SFDouble field specifies one double-precision floating point number. MFDouble specifies zero or more double-precision floating point numbers. SFDoubles and MFDoubles are represented in a VRML file as specified in the respective encoding. The initial value of an unitialized SFDouble field is 0.0.