[Bf-committers] Weekly irc meeting, october 4 2009

[Brecht Van Lommel]

Hi,

On Mon, Oct 5, 2009 at 7:59 AM, Toni Alatalo <antont at kyperjokki.fi> wrote:
> Matt Ebb kirjoitti:
>>> - Dalai prefers to see more advanced support being added for python
>>> script dependencies, like executing a script on changing a variable in
>>> the UI. Issue is that this requires an updated dependency graph
>>>
>> Couldn't this be done with notifiers  and python listeners? Would be
>> extremely useful for a lot of other situations too.
>>
>
> Yes I figure many kinds of editing tools or something just working
> inside Blender would easily benefit from these, like perhaps procedural
> tools that want to know that their base has been edited.

I think that a good notifier system that python can plug into is
important, however I also think in most cases it is not the right
solution. If you have for example a procedural tool that changes a
mesh each time you modify a parameter, that's an operator or a
modifier. If you need to re-run the script when a variable changes in
the UI, that may be the case sometimes, but I don't think that's a
reliable way to extend Blender. Similarly doing things on frame
changes may be nice, but it's not really the right thing to do either
in most cases, since there are other cases updates are needed besides
frame changes. It may be more appropriate to write a constraint for
example.

The advantage of being able to listen to such a notifier is of course
that you can extend Blender in more flexible ways, and for that reason
we should allow it. But when possible, we should allow scripts to hook
into existing Blender systems that get correctly handled by the
dependency graph, undo/redo system, duplicating data, etc. That way
things work correctly when manipulating data, running on render farms,
executing as part of macros, etc.

Now, I don't know what Dalai wanted to use this for exactly, but I
think it's important he explains it, and we think of how it can fit
in, rather than assume notifiers are the solution.

Brecht.