how to align 3d models with objects in unity. I've positioned the model on the wto point but it still doesn't fit.
as in the following image:
the method you are using is already the right one. The object might not be very well suited for image based tracking, though. There is the possibility to use the 3D model of the object for tracking purposes as well (if the 3D model closely resembles the real object). You can join the beta program here: https://www.wikitude.com/3d-model-based-object-tracking/
Do you see a better alignment of the augmentation from different angles?
Honestly, I don't know much about this field, but in my opinion, maybe the subject is not suitable? Or like you can use a script to calculate the exact sizes of all your meshes and stuff and have the script align vertexes for you less simply... you can set everything's center based on distance from origin and factor in the actual size of the object, which would be very very very difficult and time consuming
simplest we become what we behold
what you want to do is however very easy using something like blender, maya, etc...
I hope it helps you.