EDIT:
As of DF 34.07 Limbs and Joints now respect STRUCTUAL tissues, thus ABS is almost redundant and unneeded.
I say almost because some creatures you make you might wish to make limb like bodyparts, but leave out the 'grapple' function.
All depends on what you make.
I have decided to share how I made breaking joints and bones in limbs to respect RL pain/function/and Phycological crippling.
By this I mean if someone breaks their upperarm bone or their elbow, they are not very excited about using that limb until that bone is healed
So to create this effect you will need to alter
"b_detail_plan_default.txt" and "body_default.txt"
1.you will also need to alter the bone tissue template (note doing this may cause spinal bone from crippling/suffocating the creature if damaged)
or
2.add a new bone tissue template (this will give some more direct control over what willl give cripple effect)
Ok now into the nitty gritty:
1. first thing to do is open up: "body_default.txt"
2. Add [NERVOUS] to all BP's that are GRASP,STANCE,ARM,ARM_UPPER,ARM_LOWER,LEG,LEG_LOWER,LEG_UPPER,JOINT
^^^Basically add [NERVOUS] to all Body parts that are a LIMB and a JOINT^^^
NOTE: you acually dont need to add [NERVOUS] to GRASP and STANCE body parts due to the fact that once those bodyparts have all their STRUCTUAL tissues broken they lose function
3. Open "tissue_template_default.txt" and 1 of 2 can be done.
3.1 Add [FUNCTIONAL] to the "BONE_TEMPLATE" which might have a weird effect of killing the creature from a broken spine bone (or could make it require the NERVOUS and BONE tissues to be damaged)
3.2 Copy "BONE_TEMPLATE" and call it "BONEF_TEMPLATE" and simply add [FUNCTIONAL] to it.
NOTE if you did 3.2 continue with the rest of the steps, if you did 3.1 then you have just made every living creature have an ABS
4.2 Open "b_detail_plan_default.txt"
5.2 goto "STANDARD_TISSUES" and add [ADD_TISSUE:BONEF:BONEF_TEMPLATE] to the bottem
6.2 goto "VERTEBRATE_TISSUE_LAYERS" and change all ARG4 on the LIMB/JOINT categories to BONEF
You have now added ABS to all living organic creatures and will now suffer from broken bones and severed nerves for cripplings
How does this work?
I guess I will have to explain how all these tags and tissues work then. Ok then:
Now if a Bodypart has a [THOUGHT]/[NERVOUS]/[SIGHT]/etc.. tag on it, then that BP now performs that given function (thus the need of FUNCTIONAL tissues)
Also GRASP and STANCE bodyparts respect STRUCTUAL tissues instead of FUNCTIONAL tissues.
ok now for a deeper detail on how Bodyparts and Tissues work together to simulate RL I Will use a BRAIN and SPINE as an example
BRAIN has the [THOUGHT] tag thus without it the creature would simply die, and since the BRAIN is made from one material/tissue getting hit will basically end the creature's life.
[TISSUE_TEMPLATE:BRAIN_TEMPLATE]
[TISSUE_NAME:soft tissue:NP] - this is a modified organ naming convention in Regeneration to make combat logs look less... wacky.
[FUNCTIONAL]
[STRUCTURAL]
[SCARS]
[TISSUE_MATERIAL:LOCAL_CREATURE_MAT:BRAIN]
[RELATIVE_THICKNESS:1]
[VASCULAR:3]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
SPINE has [NERVOUS] which gives it power over all "Children" bodyparts (lower spine controls the Lower Body and anything connected to it.)
Now the SPINE is made from two tissues NERVE and BONE, in which the NERVE tissue is the important factor in this only because of the fact NERVE is a FUNCTIONAL tissue.
And since BONE is not FUNCTIONAL (by default, not by the means of ABS 3.1) even if it is broken or damaged the SPINE will continue to work just as long as the NERVE tissue is undamaged.
So with this Body Parts that have a "function" like THOUGHT, SIGHT, NERVOUS, SMELL, etc... Can be stopped by damaging the FUNCTIONAL tissues they have/made up of
Examples of how this works goes as this:
Dwarf1 punches Elf1 in the upper arm shattering the bone, Elf1 loses hold of the iron short sword
ABS adds a sense of Realism to DF getting rid of the vanilla "My arm is broken but I can still swing my sword 'cause my hand is perfectly fine"