Creating a group of objects

[guija]

Hi, I would like to create a group of objects together and then apply transformations / animations once to the group to have a nicer model.

For example:

• Create two spheres (a small one and big one).
• Position one sphere on the surface of the other space
• Group them together.
• Apply transformation (e.g. rotation) around center of primary (big sphere).

I'm a bit confused by the different types and and layers of abstraction are not clear to me as there are many (CpuModel, Model, ModelPart, Gm, Geometry etc.), and some cannot be instanced like (ModelPart). Is there any documentation for this that I have overlooked? From the documentations of the structs themselves it is also not clear to me.
Does someone have an idea how to do this?

[asny]

Hi. I'll try to explain each concept, but overall, I think you should just create your own struct that does exactly what your want and inside that use two Gms, one for the small sphere and one for the big sphere.

• Geometry - Some kind of geometry, for example a triangle Mesh, InstancedMesh, ParticleSystem, Circle, Rectangle, Sprites etc. You can also create a geometry yourself by implementing the Geometry trait.
• Material - Some kind of material, for example PhysicalMaterial, ColorMaterial etc. Again, you can also implement your own material by implementing the Material trait.
• Gm - A combination of any type of Geometry + Material <-- this can be rendered

These are the main concepts, so this is what you actually need in your case. It could look like:

Because it implements IntoIterator, you can call render functions directly with a references to an instance of Spheres.

Other concepts:

• Mesh - A common type of geometry. The data is transferred from the CPU to the GPU by constructing a Mesh from a CpuMesh.
• Model - A common combination of geometries and materials ie. a 3D model consisting of potentially many separate parts (ModelPart). The geometry type is always a Mesh and the material is always the same for all parts of the model. This is usually constructed by loading from a file (.obj, .gltf or similar) into a CpuModel and then transferring the data to the GPU by constructing a Model. This also handles animations which is the main reason for it's existence, so if you don't need animations and you don't load it from a file, you don't need it.

[guija]

Thanks @asny, actually i want this especially because I want to animate it. Your approach is nice, thanks and that would work I guess, but then I would probably add some animation trait and it seems like it would be similar to the model?

[asny]

Ah ok, then yeah, it sounds like you can use the Model. And no problem 🙂

[guija]

Alright, thanks, then I will try to merge a set of GMs into a model.