[Bf-committers] Layer system

[Matt Ebb]

On 22/12/2007, at 2:18 PM, Stephen Swaney wrote:

> On Sat, Dec 22, 2007 at 01:38:47PM +1100, Matt Ebb wrote:
>>
>> Erm, no, an object can most definitely be in more than one group.
>
> If you can put objects in muliple groups and you can put groups in
> layers, then you essentially have an infinite number of layers  and
> still have the simplicity of the current layer system as a top level  
> of
> organization..

No you don't, not at all, though being able to use the visibility/ 
renderability flags for groups would go a long way to help this.

I think a lot of people commenting here don't see the limitations in  
Blender's ancient layer system because for simple things, Blender  
works just fine. Even to the extent of doing one task (i.e. modelling  
or animation only) the system holds up ok, but as soon as you start  
doing things that are more complex, in a production environment where  
you need to manage the files containing all sorts of models,  
animation, lights, render settings, the whole things gets so caught up  
in spaghetti complexity, that it's a real pain.

One thing that really doesn't help the situation is that layers in  
Blender are (ab)used for all sorts of only slightly related things. As  
a method of organisation, a simplistic one-size-fits-all approach  
breaks down when there are multiple things you want to organise for  
different tasks.

For example, layers are used for;
* 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.
* 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)
* And probably one or two other things I've forgotten too.

The trouble with this, is that these tasks often have logically  
nothing to do with each other at all, and so the usage conflicts.  
Defining objects that you want as a render pass image generally has  
nothing to do with how you want to organise your scene to disable high  
poly geometry in the view, but you're force to use the same system for  
it all. It's like using the Dewey decimal system to organise both your  
books and the species of the animal kingdom.

Currently the way to work around this mess is to split your object  
layers up even more finely grained and do stupid tricks like putting  
objects on multiple layers, not because it makes more sense to  
organise it that way, but because you have to work around the system  
to make it happy, and end up with something that's barely organised at  
all. And of course doing all this stuff just uses more and more of the  
hugely limiting number of 20 layers, which I run up against quite often.

Especially doing things like that when you have all sorts of  
convoluted links and objects on multiple layers, it's very easy to  
make mistakes and get lost in it all. It's very easy to forget that an  
object is on multiple layers, and it can get cleared so easily with a  
simple stroke of a muscle-memorised M->number key->Enter. And then you  
find out after rendering for a few hours that you moved a particle  
deflector to the wrong layer by accident while trying to work around  
it all, and you have to re-render the shot again. It's all very  
frustrating.

Anyway, I'm not sure if I have any real answers, though the whole  
problem is a lot more complex of whether to use bitflags or linked  
lists. Two things would probably help a lot:
* Adding the toggles for view/select/render to groups
* Adding an option for lamps to limit their effect to a certain group,  
like the layer option.

cheers

Matt