About converting max to blender and then obj - I will do a fast explanation: (thanks to RESMAS)
1 - open max file
2 - select object you want - go to "export selection"
3 - export as "obj" default settings to Blender preset
4 - open Blender - import obj - select file
5 - blender imported the obj so now you need to see the size of the object and rescale to the size you want (many max files come in many many scales...sometimes is meters, other times is millimeters) In blender you set to the size you need the "obj" file.
6 - export as "obj" so you can use it in Octane StandALone
This is a simple export from max to "obj", but the problem is that most of the times when you export from Max, the materials are lost...and the obj comes with only 1 material to all geometry. This is the hard part....
To help yoy can do this.
1 - open max file
2 - open max material editor
3 - there is a icon - "a red cross icon" - Reset Map/Mtl to default settings
4 - this will clear the Vray maps/mtl...and then you should have the "clean" obj exported geometry
5 - open blender and set adjust the scale of the geometry
6 - export as "obj" so you can use it in Octane StandALone