1. Any model compiled with at least one jigglebone and at least one $sequence that uses a predelta or delta option.
   
2. Any model that uses the Proportion Trick and at least one jigglebone, because the trick uses a predelta option in a $sequence.
   
3. Any model compiled that has a $sequence that refers to a $poseparameter and that uses a predelta or delta option.

Crowbar decompiles animation data as best it can, but for certain animations, not all of the original data is stored in the MDL. When a model uses subtract or presubtract options, there are two animations given to the model compiler, and a predelta or delta option given to the $sequence that uses the combined animation. The compiler combines the two animations and then stores only one of the original animations and the resulting combined animation. Thus, when Crowbar tries to decompile, it can not undo the combination because one of the original animations is not in the MDL; also, even though one of the animations stored in the MDL was used in the combination, there is no indication which animation was used.

So, Crowbar writes the QC such that a recompile is possible, but leaves out the presubtract and subtract options because the decompiled animations have already been combined. However, this somehow messes up the jigglebones.

This guide presents a workaround to allow you to recompile by making a few changes to the decompiled files. Eventually this workaround would be built into Crowbar directly, but I am not sure when that will happen.

I do not know exactly why this workaround works, but it seems like the jigglebones and pose parameters need to be re-combined back into the combined animations.

The workaround has 3 main steps, described in their own sections:

• Step 1: Create a special SMD file for each $sequence block that use predelta or delta options.
  
• Step 2: Change the $sequence blocks (or the $animation blocks that a $sequence uses) that use predelta or delta options.
  
• Step 3: Add a new $animation block, for each special SMD file, to the QC file before any other $animation or $sequence blocks.

• In the QC file, find all $sequence blocks that have a predelta or delta option.
  For example: A model using Proportion Trick would have this:
  $sequence "proportions" { "a_proportions" autoplay predelta fadein 0.2 fadeout 0.2 }
  
  
• For each found $sequence block, copy each SMD file used and name each something like "subtract_zero_01.smd" (where the number 01 is changed to make each copy unique).
  For example, for only one needed special SMD file: Copy "a_proportions.smd" file to "subtract_zero.smd" file.
  For example, for two needed special SMD files: Copy "walk.smd" file to "subtract_zero_01.smd" file. Copy "run.smd" file to "subtract_zero_02.smd" file.
  
  
• In the new special SMD (e.g. "subtract_zero.smd"), for each bone in nodes section that does not have a -1 (which means it is not a root bone; usually there is only one root bone), remove that bone's line from the skeleton section.
  For example:
  Original nodes and skeleton sections (note that the first line in nodes section has -1 at the end of it):
  
  nodes 0 "ValveBiped.Bip01_Pelvis" -1 1 "ValveBiped.Bip01_Spine" 0 2 "ValveBiped.Bip01_Spine1" 1 // lines for bones/nodes 3 through 79 removed for easier reading 80 "Tail1" 0 81 "LTail" 80 82 "RTail" 80 end skeleton time 0 0 -0.000008 -5.062500 3.064453 0.000000 0.000000 -1.570796 1 0.000006 -3.861328 2.015625 0.000000 0.000000 0.000000 2 -3.814453 0.000000 0.000000 0.000000 0.000000 0.000000 // lines for bones/nodes 3 through 79 removed for easier reading 80 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 81 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 82 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 end
  The skeleton section after deleting the bone lines:
  
  skeleton time 0 0 -0.000008 -5.062500 3.064453 0.000000 0.000000 -1.570796 end
  
  
• Zero-out the 2nd, 3rd, and 4th values (these are the position values) for each bone line in the skeleton section.
  For example:
  Change the skeleton section from:
  
  skeleton time 0 0 -0.000008 -5.062500 3.064453 0.000000 0.000000 -1.570796 end
  to:
  
  skeleton time 0 0 0 0 0 0.000000 0.000000 -1.570796 end

For each $sequence block (or each $animation block that a $sequence uses) that uses a delta or predelta option, add:
(where subtract_zero is the name given the special SMD file created for this $sequence in Step 1.)
Note that the same special SMD file is used for all $animation blocks that a $sequence uses.
For example:

For example: Corresponding to the examples shown in other steps, only one $animation block is needed: For example: Multiple special SMD $animation blocks would look like this: