importing 3D format into custom made 3D program

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C#

Hey all,
I have been creating a pet 3D project in my spare time with many common features to Blender and 3DS Max. I liked the programs that much I thought I would make alternatives by hand as a technical exercise.

I was just wondering if anyone has had any previous use of the existing 3D formats? e.g .3DS .OBJ .FBX. I know .FBX is human readable. How would one suggest exporting/importing model files to my program? (It can already save in its own format but I would like the functionality of other formats)

Here's my world structure
There can be any number of triangles in a model and any model can reference triangles from another model

--Scene-
    |-----Model---Triangle-MatID1
    |           |-Triangle-MatID1
    |           |-Triangle-MatID1
    |           |-Location
    |           |-Rotation
    |
    |-----Model---Triangle-MatID2
    |           |-Triangle-MatID2
    |           |-Triangle-MatID2
    |           |-Location
    |           |-Rotation
    |
    |----OmniLight=(Location, Intesity, Colour)
    |
    |----Camera(Location, LookVector)

Thank you all in advance :)