Import a Godot Packed Scene into ECS

[fire]

• Status: proposed
• Deciders: @fire @AndreaCatania
• Date: 2021-02-12

Context and Problem Statement

Not able to use the standard Godot import tooling to import entities. We want to import the packed scene into entity and entity3d format.

Decision Drivers

• We lack content in the ECS ecosystem
• It's mindless to convert
• Converting should be not noticeably slow
• Blocks ECS skeletons
• Blocks ECS physics engine

Considered Options

• Convert manually
• Write a plugin in C++
• Write a plugin in gdscript

Decision Outcome

Chosen option "Write a plugin in C++" because it was the fastest and does not require a separate addon.

Positive Consequences

• Fastest
• Can be in the single Godot executable

Negative Consequences

• Hard to bug fix

Pros and Cons of the Options

Option convert manually

We go over the packed scene and convert them to a packed scene using Godex components. Godex components are added based on the type and the properties.

• Node3D (base class and only the base class)
  • Hierarchy of nodes, and the transform.
• MeshInstance3D (without skeleton)
  • Hierarchy of nodes, the mesh and the transform.
• MeshInstance3D (with skeleton)
  • passthrough
• BoneAttachment3D
  • passthrough
• Skeleton3D
  • passthrough
• MultiMeshInstance3D
  • passthrough
• CSGShape3D
  • passthrough
• GridMap
  • passthrough
• Camera3D
  • passthrough
• Light3D
  • passthrough
• AnimationPlayer
  • passthrough

For Node2D we passthrough.

Everything else stays the same until we have a conversion for it.

• Good, Know exactly what we want
• Bad, because there are ways to do the conversion wrong by human error

Option GDScript

Automate manual option in GDscript.

• Good, it's easy to iterate
• Bad, because it's not embedded

Option C++

Automate manual option in C++.

In scene importer add a checkbox for conversion and it is enabled by default.

• Good, it's embedded
• Good, it's fast
• Bad, because of C++ programming friction

Links

• https://github.com/adr/madr#the-template

[AndreaCatania]

The Entities that need to stay in the hierarchy, need a Child component. So don't forget to add it, when you have nested Entities.

[AndreaCatania]

I made a scene converter here https://gist.github.com/AndreaCatania/afd01671e35e9d004d1d7a498fc0e2a3, I will improve it overtime. I've also a wiki here: https://github.com/GodotECS/godex/wiki/Godex-importer

[AndreaCatania]

Moving the proposal to discussions to keep the issue just for things to fix.