Thank you for bringing your question to our community forum 
A few quick questions and comments.
- Can you please provide some more information about how you are importing and initialing your 3D model?
- I would love to see some of the methods that you have tried so far for changing the lighting in your scene. Can you please share a sandcastle demo with your current progress?
- As you may know, you can edit the time of day (sun orientation). I suggest that you experiment with this. There is likely a time of day that works best for your model.
Please let me know if you have any additional questions or concerns.
-Sam