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Model structure

S

Swezam

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5
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sweden
Hello everyone!

I am not new to 3D modelling but I am new to blender and creating assets for an engine. My previous experience is from 3D printing and for that you do not really have to think about performance and optimization. So as I am learning to modell in blender I have stumbled upon a few questions that I hope you guys can help me out with.

When it comes to designing for example an airport how should one think about the model structure? For example, if I design an airport terminal in blender that is built up using 3 separate objects/meshes in blender and I export it as one BGL, does MSFS see it as 1 object or 3 separate objects in one BGL? Is it even possible to export 3 separate objects as one BGL or does it need to be contained into one mesh? I am asking because I don't understand if I should try to keep everything as one mesh or if it is okay to build up a terminal using several meshes.

What is the best way of determining what should be combined and what should be separate? How does it affect the performance in the sim?

Thank you in advance for any insight!
 
MSFS will see the airport terminal as three separate objects. The individual parts of the model will remain individual even when compiled into the BGL file (aircraft models require this behaviour to work otherwise you wouldn't be able to have parts like ailerons and rudders move).

For a very large terminal you're probably going to want to separate it out into individual parts. Think about being parked at a huge terminal with half of the terminal behind you. If that part of the terminal is a separate part then MSFS can easily exclude it if it's position and size puts it out of the users view. If it's part of a single mesh then that's a lot of time spent calculating if each individual polygon is visible or not.

For ease of modeling you may want to make the main section of the terminal one part but any extra bits and pieces would be better off being kept as separate parts. There are a couple of reasons for this:

As I said earlier, if you have a part that is not visible then MSFS will simply not need to draw it. I don't know exactly how the graphics engine of MSFS works but any decent graphics engine would do a quick check of a parts position and size and exclude anything outside the field of view. This top level culling can save a lot of work later on in the process. If that individual part is part of a larger mesh which is partially visible then the engine would next determine if the each individual polygon is within view before culling it. It comes down to checking if 1 part is visible versus checking if 100 polygons are visible.

The second reason is LODs. This is where you make simpler models that are drawn as the object gets further away. Keeping you meshes separate can make life a lot easier when it comes time to reduce the complexity of the model.

Keep in mind that MSFS will also not draw any part that is very small. Developers have this issue with small parts such as runway cones. You want the cones to be visible even from very far away but MSFS will not them which can lead to them appearing to pop in. Putting an extra polygon a few metres below ground makes the cone seem larger as far as the graphics engine is concerned and thus makes them more visible from further away.

See here for information about LODs:

LODs

docs.flightsimulator.com docs.flightsimulator.com

See here for information about all the other stuff I've talked about:

Landscape Elements

docs.flightsimulator.com docs.flightsimulator.com
 
Wow thank you so much for taking the time to answer my questions. I also had a look at the links you provided. I feel like I have a much better grasp of what I needed to know. Best wishes!
 
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