How to save a 3D scene on a file and open it ?

Hello, I'm wondering how to save a 3D scene in a file ( using WriteFile ? ). And, with AlphaGUI, when you click on a button to import the file, all the 3D objects that you saved are in the map.
I hope I have been understood.

I'm not sure what you mean by a scene, but you can create any kind of mesh, and save all its data to a good old fashioned txt file using the various file commands. It takes patience, but it's the method I prefer, because you end up with a full understanding of what you've created, not to mention the confidence of knowing you can basically make your own mesh files. Of course, using a 3d modeler is much easier, but I don't have that many gold coins lying around XD

Anyway, start from scratch studying the mesh creation and file commands, and you'll understand it all eventually. I did once, and I was a total beginner back then.

So, you're making a world editor? Check here for any code that may help in your doings.

https://archive.blitzcoder.org/

Also, download this and study the B3D file format document included.
https://jfkeo1010etc.itch.io/blitz3d-goodies-collection/comments

I made a world editor that creates a mesh out of all the geometry I placed, exports level objects(like ammo box items)as pivots, and saves it all into a blitz3d .B3D file. The built-in LoadAnimMesh() function can load a hierarchy of all the meshes/pivots for easy level loading.

Utilizing the B3D format is the best way for world building/loading, though you can create your own scene file format if you want.