Remove REST transform influence in skeleton bones

[reduz]

Implements: godotengine/godot-proposals#3377

• Animations and Skeletons are now pose-only.
• Rest transform is kept as reference (when it exists) and for IK
• Removed custom bone poses (redundant with local and global pose overrides).
• Improves 3D model compatibility (non uniform transforms will properly work, as well as all animations coming from Autodesk products).

This is a compatibility breaking change.

[TokageItLab]

@reduz It make to crash when selecting Skeleton in the SceneTreeDock after importing gltf assets and makeing inherited scene.

skelman.gltf.zip

ERROR: Condition "p_skin.is_null()" is true. Returning: Ref<SkinReference>()
   at: register_skin (scene/3d/skeleton_3d.cpp:972)

================================================================
handle_crash: Program crashed with signal 11
Engine version: Godot Engine v4.0.dev.custom_build (687fd77c6b2840b07fadc991f1e65ee4c0710ce9)
Dumping the backtrace. Please include this when reporting the bug on https://github.com/godotengine/godot/issues
[1] 1   libsystem_platform.dylib            0x00007fff20395d7d _sigtramp + 29
[2] 2   ???                                 0x00007fc601cd0c10 0x0 + 140488410467344
[3] Ref<Skin>::Ref(Ref<Skin> const&) (in godot.osx.tools.x86_64) (ref_counted.h:178)
[4] Ref<Skin>::Ref(Ref<Skin> const&) (in godot.osx.tools.x86_64) (ref_counted.h:178)
[5] SkinReference::get_skin() const (in godot.osx.tools.x86_64) (skeleton_3d.cpp:59)
[6] MeshInstance3D::_resolve_skeleton_path() (in godot.osx.tools.x86_64) (mesh_instance_3d.cpp:152)
[7] MeshInstance3D::_notification(int) (in godot.osx.tools.x86_64) (mesh_instance_3d.cpp:312)
[8] MeshInstance3D::_notificationv(int, bool) (in godot.osx.tools.x86_64) (mesh_instance_3d.h:40)
[9] Object::notification(int, bool) (in godot.osx.tools.x86_64) (object.cpp:841)
[10] Node::_propagate_enter_tree() (in godot.osx.tools.x86_64) (node.cpp:214)
[11] Node::_set_tree(SceneTree*) (in godot.osx.tools.x86_64) (node.cpp:2451)
[12] Node::_add_child_nocheck(Node*, StringName const&) (in godot.osx.tools.x86_64) (node.cpp:0)
[13] Node::add_child(Node*, bool, Node::InternalMode) (in godot.osx.tools.x86_64) (node.cpp:1125)
[14] Skeleton3DEditor::create_editors() (in godot.osx.tools.x86_64) (skeleton_3d_editor_plugin.cpp:784)
[15] Skeleton3DEditor::_notification(int) (in godot.osx.tools.x86_64) (skeleton_3d_editor_plugin.cpp:839)
[16] Skeleton3DEditor::_notificationv(int, bool) (in godot.osx.tools.x86_64) (skeleton_3d_editor_plugin.h:126)
[17] Object::notification(int, bool) (in godot.osx.tools.x86_64) (object.cpp:841)
[18] Node::_propagate_enter_tree() (in godot.osx.tools.x86_64) (node.cpp:214)
[19] Node::_set_tree(SceneTree*) (in godot.osx.tools.x86_64) (node.cpp:2451)
[20] Node::_add_child_nocheck(Node*, StringName const&) (in godot.osx.tools.x86_64) (node.cpp:0)
[21] Node::add_child(Node*, bool, Node::InternalMode) (in godot.osx.tools.x86_64) (node.cpp:1125)
[22] EditorInspector::_parse_added_editors(VBoxContainer*, Ref<EditorInspectorPlugin>) (in godot.osx.tools.x86_64) (editor_inspector.cpp:2290)
[23] EditorInspector::update_tree() (in godot.osx.tools.x86_64) (editor_inspector.cpp:2426)
[24] EditorInspector::edit(Object*) (in godot.osx.tools.x86_64) (editor_inspector.cpp:2957)
[25] EditorNode::_edit_current() (in godot.osx.tools.x86_64) (editor_node.cpp:2173)
[26] EditorNode::push_item(Object*, String const&, bool) (in godot.osx.tools.x86_64) (editor_node.cpp:2079)
[27] SceneTreeDock::_node_selected() (in godot.osx.tools.x86_64) (scene_tree_dock.cpp:1375)
[28] void call_with_variant_args_helper<SceneTreeDock>(SceneTreeDock*, void (SceneTreeDock::*)(), Variant const**, Callable::CallError&, IndexSequence<>) (in godot.osx.tools.x86_64) (binder_common.h:227)
[29] void call_with_variant_args<SceneTreeDock>(SceneTreeDock*, void (SceneTreeDock::*)(), Variant const**, int, Callable::CallError&) (in godot.osx.tools.x86_64) (binder_common.h:337)
[30] CallableCustomMethodPointer<SceneTreeDock>::call(Variant const**, int, Variant&, Callable::CallError&) const (in godot.osx.tools.x86_64) (callable_method_pointer.h:97)
[31] Callable::call(Variant const**, int, Variant&, Callable::CallError&) const (in godot.osx.tools.x86_64) (callable.cpp:51)
[32] MessageQueue::_call_function(Callable const&, Variant const*, int, bool) (in godot.osx.tools.x86_64) (message_queue.cpp:258)
[33] MessageQueue::flush() (in godot.osx.tools.x86_64) (message_queue.cpp:306)
[34] SceneTree::process(double) (in godot.osx.tools.x86_64) (scene_tree.cpp:448)
[35] Main::iteration() (in godot.osx.tools.x86_64) (main.cpp:2570)
[36] OS_OSX::run() (in godot.osx.tools.x86_64) (os_osx.mm:510)
[37] main (in godot.osx.tools.x86_64) (godot_main_osx.mm:79)
[38] 38  libdyld.dylib                       0x00007fff2036bf3d start + 1
-- END OF BACKTRACE --
================================================================

[TokageItLab]

Previously, skin was dynamically generated when p_skin was null. This is a case that can occur when calling from within MeshInstance3D. If you don't want to generate it in the Skeleton3D::register_skin(), you need to generate the skin in MeshInstance3D.

This is a patch to keep the previous behavior.

diff --git a/scene/3d/mesh_instance_3d.cpp b/scene/3d/mesh_instance_3d.cpp
index 67f4a88228..cfd90e5da0 100644
--- a/scene/3d/mesh_instance_3d.cpp
+++ b/scene/3d/mesh_instance_3d.cpp
@@ -146,11 +146,13 @@ void MeshInstance3D::_resolve_skeleton_path() {
 	if (!skeleton_path.is_empty()) {
 		Skeleton3D *skeleton = Object::cast_to<Skeleton3D>(get_node(skeleton_path));
 		if (skeleton) {
-			new_skin_reference = skeleton->register_skin(skin_internal);
 			if (skin_internal.is_null()) {
+				new_skin_reference = skeleton->register_skin(skeleton->create_skin_from_rest_transforms());
 				//a skin was created for us
 				skin_internal = new_skin_reference->get_skin();
 				notify_property_list_changed();
+			} else {
+				new_skin_reference = skeleton->register_skin(skin_internal);
 			}
 		}
 	}

[TokageItLab]

Animation key insertion in SkeletonEditor and Inspector is broken, but this is not in the scope of this PR as it is an effect of getting rid of the previous Transform3DTrack. I will send you a PR with a fix after @reduz 's some overhauls to the animation features are done.

[TokageItLab]

Also, it seems that the InitPose and ApplyPoseToRest functions of SkeletonEditor are broken. This is the effect of this PR, but at least considering the fact that the calculation of rest in skinning is correct, it can be fixed later...

[reduz]

@TokageItLab Regarding key insertion, I think we need to add a TRS key insertion menu in the 3D editor similar to the 2D one, also asking for using either the new TRS tracks or beziers:

[reduz]

@TokageItLab alright applied your suggested patch

[TokageItLab]

@TokageItLab Regarding key insertion, I think we need to add a TRS key insertion menu in the 3D editor similar to the 2D one, also asking for using either the new TRS tracks or beziers:

Roger, for now, I'll fix the broken track assignments and work on the implementation of the transform record in a separate PR.

[lyuma]

Reviewed together with @fire

[reduz]

Thanks! Will merge when CI completes and move on to the next task.