[Bf-committers] Layer system

[Martin Poirier]

For the sake of comparison, I'll split your list in
two sublist:

List 1:

> * Hiding and showing models, for example to hide
> unwanted 'trash'  
> stuff, or to use temporarily to hide high-poly
> objects to speed up  
> interactive display, or to hide away helper objects
> like armatures or  
> curve guides or force fields that may be getting in
> the way
> * Defining render layers, determining what objects
> will appear in  
> different image buffers in the compositor upon
> rendering.

List 2:

> * Defining what lamps will affect what geometry
> ('layer' option)
> * Controlling the effect of particle
> systems/deflectors (this one is  
> utterly ridiculous, force fields will only affect
> particles systems on  
> the same layer, which swiftly ruins your
> organisation of different  
> systems/helpers, especially if you have multiple
> systems sharing force  
> fields)

List 1 mostly deals with visibility. What should be
visible and when.

List 2 mostly deals with functionality. What should
affect/functions with what.

IMHO, all of those in list 2 would be much better done
with Groups. Using Layers is "convenient" because it's
often simpler to do (both programatically speaking and
for the user), the problem, as you so well illustrated
is that it couples a lot of different functions into
system that is not made for that.

As I see it, Layers represent visibility groupings and
Groups represent functionality groupings, there's no
good reasons for visibility groups to be used for
functionality groups and vice versa.

Also, both require slightly different functionality
from a user point of view:

Layers should have quick visibility toggles
Groups should have a simple way to see (and select)
all objects belonging to a group.

And probably more.

> Anyway, I'm not sure if I have any real answers

Concrete examples and discussions of features is
always good.

> though the whole  
> problem is a lot more complex of whether to use
> bitflags or linked  
> lists. 

Indeed. As I said, back end storage is perfectly
decoupled from grouping functionality.

Regards,
Martin


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