[Bf-committers] GSoC 2016 Preliminary proposal to optimize the memory usage of mesh undo

[Campbell Barton]

On Sat, Mar 5, 2016 at 8:19 PM, Ounan Ding <ounanding at gmail.com> wrote:
> Hi,
>
> I am Ounan Ding(IRC: TheBusyTypist).
> I am interested in Blender and willing to contribute to our community in
> the coming GSoC 2016.
>
> Here is my preliminary proposal to optimize the memory usage of mesh undo:
>
>
> https://github.com/thebusytypist/gsoc-2016-doc/raw/master/proposals/mesh-undo-memory/mesh-undo-memory.pdf

Checked over the document, one thing which isn't quite correct is the
statement that...

  "The current strategy is that the whole mesh data get duplicated and restored
on the undo command"

... in fact each chunk of memory is compared and only stored if there
are differences,
though this is inefficient when making destructive changes to the mesh
(subdivision for example),
it does mean changing selection won't have to store  UV's, weights,
shape-keys etc.

One possible optimization would be to implement binary diffing, so
minor differences to large allocates don't have to store the entire
block each time.

> (and I put it on wiki.blender.org as well:
> http://wiki.blender.org/index.php/User:TheBusyTypist/GSoC2016-Mesh-Undo-Memory
> But I suggest to read above pdf version since it has better typesetting)
>
> I have a review of current implementation here:
> http://blender.linearconstraints.net/2016/02/28/notes-on-undo.html
> It helps me form this proposal.
>
> I also have some notes and practice on the Blender Operator system:
> http://blender.linearconstraints.net/2015/03/28/write-first-blender-operator.html
> http://blender.linearconstraints.net/2015/04/01/analyze-primitive-cube-add-operator.html
> which lead me to the design in my proposal.
>
> Currently I am still working on more strategies for specific Operators.
> I am also looking forward to commends and critiques from you.
>
> Thank you.
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-- 
- Campbell