Design general model inside ignition (Citadel or Fortress)

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How do you design models just like this: https://app.ignitionrobotics.org/fuel...

I wanted to start, but I'm not sure where. I know the cheating way only by using Blender and import it to .DAE or .OBJ. That's it.

How do you guys do this?

Update #1 in Feb 16 1:09 PM EST: Oof! I used Blender and exported .obj AND .dae file format.

Now it couldn't load them. I must have done something wrong. I was able to load dae from this link, but not my own file. This has to be from the program