The offline SH3D file has a few parts that are not readable text -- are those just the images for surface textures?
This can be icons, texture images or 3ds files.What amount of difference is there between formats?
There's no difference, it's the same format: a zip file containing a Home entry created with Java serialization, which references images and 3D models displayed in the saved home. In the case of an offline SH3D file, these images and 3D models are directly stored as additional entries in the zip file, making it completely independent of the current furniture and textures catalogs, to ensure it can be exchanged.
In the case of an online SH3D stream, the Home entry references images and 3D models as URLs when this data is available on the web server. Thus, such a stream is generally much smaller and contains more than a Home entry only if the user imported a background image, furniture or textures.
A smaller SH3D stream doesn't mean a faster file opening since all the images and 3D models files have to be downloaded afterwards, but it means a faster saving since the images and 3D models files don't have to be uploaded back to the web server. In the facts, it also means a faster file opening the second time, because Java automatically manages a cache of the downloaded images and 3D models files.
So, I could upload an offline SH3D file to the web server as the user saved it in on his computer, and then make it available as an online file. But if you followed my previous explanations, this way of doing will generally slow down file opening and much more file saving, because end users and web server don't have an infinite bandwidth (and ADSL provides a much smaller upload bandwidth).
To transform an offline SH3D file to an online SH3D file, you just have to replace in its Home entry the references to the entries of the SH3D file by references to their matching URLs. It's "just" some file content comparisons. Nevertheless, as a Home entry is created with Java serialization, it should be much easier to program this in Java than in Python.
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Emmanuel Puybaret, Sweet Home 3D creator
