[Bf-committers] Expanding the number of layers in Blender

David Bryant aceone at bellsouth.net
Fri Dec 21 09:36:46 CET 2007


Whew!
No wonder no one want's to tackle the assignment of expanding the layer 
base! There's fragmented code everywhere and very little commenting in the 
codebase on the matter.I'm running into a lot of code that I can't wrap my 
head around.There's really no place origin to "begin" to see where the bit 
field assignments "really start" to define the layers.What I've found is 
that the even bit shifted values for layers actually define layers ( 1,2,4,8 
for layers 1,2,3,and 4 etc.). The odd values in between are for Shift 
selected layers to have two or more layers visible at the same time.
Therefore numrical values in between the bit shifted values are unusable to 
expand the layer count.(Bit fields are quick to evaluate but are not good 
for this.Too limiting).
 Also, layers are either visible or invisible.Shift selecting shouldn't 
be.Either layer visible or layer invisible.

I need someone to explain to me what the following things are:

1.v3d->lay

2.vd->lay

3.vd->layact

4.0xFF000000 (I see this value from time to time in the layer code being 
evaluated.What is it for)
I'm finding that this system has to be basically  rebuilt!

With hardcoded  code like this:
while(bit<32) {
if(vd->lay & (1<<bit)) {
vd->layact= 1<<bit;
break;
}
bit++;
}
Expanding Blender's layers (without hacking all over the place) will be very 
difficult.

There should (in theory )be a place in Blender's code that
reads:

#define NUMBER_ OF_ LAYERS  400 (or whatever you want)

Changing the number of layers should be easy as changing  a value or two in 
the codebase.
I'm finding that the layer code has to be rebuilt almost entirely if it's 
going to be code that's flexible and expandable.I've been able the expand 
the number of layers in Blender (by hacking) but it really needs some solid 
reengineering.

It also needs to be more modular.The layer code really needs it's own C 
file. As I work, I'll see if I can make that happen.

Maybe you developers can help me.I'm up to the task but to do it right, it 
might take me a month or two to complete (with some help).

At  present, my Named Layers patch in the patch tracker is fully usable and 
bug free ( to my knowledge) but only deals with the 20 present layers.This 
further endeavor is just my contribution to make Blender even more powerful.

Digikiller



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