You say you save Scene 2 to a 'different obj'.
Are you therefore changing the project_name ??
If you do this a new obj/mtl gets made BUT so does a new OCS project and that will default the materials again!!!
You have two Scenes in your SKP - 'Scene 1' and 'Scene 2'.
You export 'Scene 1' as let's say 'my_project' into a set folder - export camera and perhaps lighting settings from the SKP... it makes OBJ/MTL files ['my_project.obj' etc] and a new Octane OCS ['my_project.ocs'] as this is the first time you have run the tool, and renders it etc, you can adjust the materials etc as desired, save/close the OCS.
Make some changes to you model - e.g. move chair.
NOW in the SKP change to 'Scene 2'.
Export 'Scene 2' with the same project_name/folder... it makes new set of OBJ/MTL files ['my_project.obj' etc] - these might be the same as before, but because you might
have changed geometry or materials it is always done. It will use the existing OCS 'my_project.ocs' - it imports the updated obj and mtl file... It uses the new camera - BUT uses any settings you have saved for existing materials - any newly added or renamed materials will need adjusting by you this time. Save/close the OCS.
Now in the SKP make a new Scene = 'Scene 3'.
But do not change anything else.
Export 'Scene 3' with the same project_name/folder... it makes new set of OBJ/MTL files ['my_project.obj' etc] - again these will be the same as before, but because you might
have changed geometry or materials it is always done. It will again use the existing OCS 'my_project.ocs' - it imports the updated obj and mtl file [which haven't changed this time]... It uses the new camera AND uses the material settings you have saved for the existing materials. Save/close the OCS as desired.
Thus you now have an OCS that has its materials frozen.
Export 'Scene 1' again [same project_name/folder] and the material settings will be remembered.
Export 'Scene 1' again [but this time with a new project_name or a new project_folder] and the material settings will NOT be remembered and you must start again tweaking them.
If you do want to have more than one copy of a project with the 'same' set of materials you can do this convoluted fix...
Export the SKP's 'Scene 1' for the first time as 'my_project' [folder is also named 'my_project'] and adjust the materials as desired and save/close the OCS.
Make a copy of the 'my_project' folder [and its 'my_project.OCS'].
Name the copied folder 'my_project_B'.
Leave the OCS file named 'my_project.OCS'
Now Export SKP's 'Scene 1' still named as 'my_project' BUT with the update project_folder path ro 'my_project_B', [the OCS already exists with settings as desired from the original 'my_project']...
However, when you run Octane on this 'cloned' OCS it will still use the texture file paths previously set in the original 'my_project' folder version and NOT the cloned 'my_project_B' folder version! Aaaargh!
To truly separate the two 'projects' you really need to separate the texture file sets.
If you temporarily rename the original folder 'my_project_Textures' as 'my_project_TexturesXXX' neither project will be able to find them when opened manually, but when one is re-exported it will simply remake a correctly named folder and add the re-exported image files as needed, BUT when the 'my_project_B' version of 'my_project.ocs' runs it will have put its images into its own sub-folder BUT its OCS itself is not looking in there to find them [duh!] - this is because the paths are 'hard-wired' into the OCS, and so if the original textures folder is no longer found [e.g. it's been renamed etc] then Octane reports an error and prompts you to specify each 'missing' image file's location in turn - which is OK for a few textures but a pain for dozens... BUT after correcting each to the appropriate folder and then save/close of the OCS the two projects would now be properly separated and the OCSs will look for their own textures in their own sub-folders [as exported] - AND remember to rename the original '_Textures' without the 'XXX' !
HOWEVER, if you are up to it there is a much quicker fix... in which you do not need to rename any folders and get errors and repath each file in turn etc etc.
Ensure that the 'my_project_B' folder's 'my_project.ocs' is closed and then right-click its icon and use 'Open_With' - choose 'Notepad.exe' [or 'Notepad++.exe' if it's installed - do NOT use a word-processor - it's plain-text] - AND don't change the default app [leave the box unticked] ! just 'edit' the OCS file using the alternative app this once. An OCS file is in written in plain text - it's a kind of XML file - so it can be edited mnaually... Using 'Notepad' do a 'find_and_replace' within it - on the images' folder paths to match the correct one. For example on 'my_project' an image path entry might be like this -<linkedfilename>C:\Users\TIG\Desktop\my_project\my_project_Textures\Wood_2.jpg</linkedfilename>
If the copied project is in folder 'my_project_B' then you 'find_and_replace' "C:\Users\TIG\Desktop\my_project\" with "C:\Users\TIG\Desktop\my_project_B\" - globally - then save/close and reopen the OCS with Octane and it should now be looking at the correct textures' folder...
This re-pathing of texture-paths in a copied OCS can be automated - I am writing a simple Ruby tool to do this - I'll publish it later today...
This 'hardwiring' of the paths only applies to the texture images as other paths like the ocs itself and obj file is set in the exporter's command-file...
Similarly if you export lighting it will override the OCS default, so if you have set lights in the OCS do NOT export the SKP's lighting settings later...