[Bf-vfx] Blender data, big picture

[Ton Roosendaal]

Hi Keir,

Answers for your questions are mixed in below.

> 1) New ID: MovieClip
>
> Sorry to be stupid, but what's a "New ID"? Is this a new object type  
> like Camera or Mesh?

When in Blender a piece of data gets an "ID" prepended, it'll be a  
uniformly handled item that can be linked, appended, shared, etc. In  
Blender an "Object" is of type "ID", but also a scene, materials,  
textures, actions, nurbs, camera data and so on.
This allows such data to be used anywhere in Blender.

>  - better definition of how sequence of images works
>
> I'm not sure what this means. Are you suggesting fleshing out the  
> concept of a MovieClip is? For example, resolution, number of  
> frames, file name, etc?

Current Image-sequence definition is quite insufficient. There's only  
a 'start' and 'end' frame number, and it needs a reference filename to  
figure out what the other frames are.
Still need to investigate this further, but ideally an artist should  
be able to select any alphabetically ordered set of files and use as  
input.

>  - ffmpg movie file support
>
> Doesn't blender already have a nice system for accessing movie  
> sequences? I remember using this some 4 years ago for my thesis.

Yep, that code can be re-used.

> - proxy level support (like 4k -> HD)
> - proxy level with files as well as making levels in memory
>
> While proxying is great, I'm not sure we'll need it for the first  
> version. I will ensure the design does not preclude adding this in  
> the future.

For me it's the bare basics. From day 1 Blender should be agnostic of  
any resolution or file type (12 or 16 bits color!) and allow playback  
of any resolution suitable for the artists' hardware.
This is Blender side, not relevant for libmv (unless libmv has a  
strange limit that it won't accept 4k frames or 16 bits data?)

> (reasoning why markers are not "ID": mostly because it's fully tied to
> a movie clip itself, no sharing is required. Via MovieClip ID markers
> can be addressed and used).
>
> I'm not entirely convinced about this. How will the markers  
> positions be stored? I would prefer if they used blender's internal  
> fcurves system, but doesn't that already suggest that they should be  
> full objects themselves?
>
> Does blender have a way of grouping objects such that the MovieClip  
> "owns" the markers / bundles but that they are still full fledged  
> objects?

Forget about "Objects" :) Blender allows anything to be animated and  
have fcurves anyway.
With the danger of confusing more; you could visualize marker points  
or bundles to be like a Blender armature (list of bones). Each bone is  
an individual item with transforms, properties and editable and  
linkable. Bones are not "Objects" in Blender. Vertices are not  
"Objects" either. Whether it's good or bad is not the issue, it's just  
how internal design works.

> - links to MovieClips
>
> By links do you mean has a dropdown that lets you select a  
> movieclip? What about a "add movie..." button?

That's inherent :)

>  - allow realtime playback of clips
>   (could become "Render -> Play Anim" as well)
>
> This will require a "scrubber" so that you can scrub back and forth.  
> This is a simple but necessary feature for practical semi-manual  
> tracking.

Yep for sure it is.

> 5) Depsgraph
> - need a way to solve all dependencies on nodes, images, movies,
> sequence.
>
> Can you expand on what this means? I know what solve means in the  
> context of a 3D reconstruction, but it's less clear in this case.

Since Blender allows relationships of nearly anything with anything  
else (via "ID" as roots), we have a dependency graph to "solve" the  
right evalutation order for items.

Dependencies can be on many levels. There's not only 3d transform- 
related dependencies (that work OK now) but also dependencies on 3D  
lighting/glsl, or dependencies of Images on other Images even. All for  
later, and typical Blender coder work. :)

-Ton-


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