[Bf-committers] Animating scene properties - getting to know the codebase

[Alberto Mardegan]

Hi there!
  I'm trying to fix https://developer.blender.org/T49658 (AKA
https://developer.blender.org/T49261), which is the bug affecting the
VSE when you insert a scene strip and its property animations get
executed with the wrong time.

I have a few questions, which I couldn't get answered by just studying
the code:


1) In source/blender/blenkernel/intern/anim_sys.c, at the end of the
BKE_animsys_evaluate_all_animation() function there's a loop which goes
through all the scenes and animates their properties:


https://git.blender.org/gitweb/gitweb.cgi/blender.git/blob/HEAD:/source/blender/blenkernel/intern/anim_sys.c#l2903

Why is this done (as opposed to just animate the current scene)? Is it
in order to support the feature of using scenes in the VSE, or are there
also other cases?


2) In the function mentioned above, I need to keep track of the scenes
I've already animated (you can have a look at
https://developer.blender.org/D2558 to see what I'm doing) in order not
to animate their properties twice. What's the best way to do that? Right
now I'm using a linked list on the stack, but maybe it could be better
to add a flag to the Scene or AnimData structure instead?


3) Am I right if I say that if the project has multiple scenes, the
BKE_animsys_evaluate_all_animation() function is likely to perform a lot
of useless computations? I mean, if a scene other than the current one
contains a lot of meshes with animations, and this scene is not used in
the VSE, all these animations are computed for no reason.


4) It seems that all meshes, lights, and all animatable things are
stored as linked lists in the Main class. Why aren't they referenced in
the Scene class (instead / as well)?
What's the way to find all animatable things present in a scene? Or
conversely, if I have a mesh, how can I tell in which scene it's being used?


Last but not least: long live the VSE! :-)

Ciao,
  Alberto