HRC Hierarchy data format
An HRC file is product of the original Playstation Psy-Q 3D development libraries. They describe the bone hierarchy of a 3D model. Most of the time they originally start as a plain text file exported from 3D editing software, or from a 3D file converter. From this they can be "compiled" into binary form more usable for the PSX.
On the PC version of Final Fantasy 7, a text HRC file is used to define the skeletal hierarchy of the field models. The Battle Models use the compiled Format.
But I think that since you read this document, you've got some knowledge 'bout 3D models and skeletons. Let's just start, this format's quite simple! ^_^
HRC file format
Since the HRC files are simple plain-text files, you can open them in notepad or any other text editor. Here are the first four bones of "abjb.hrc" (Yuffie's Hierarchy)
:HEADER_BLOCK 2 :SKELETON sd_yufi_sk :BONES 24 hip root 2.9662 1 ABJC chest hip 4.0621967 1 ABJE head chest 5.017107 1 ACAA joint head 3.5236073 0 ribon_a joint 8.52051 1 ACAF ....
The other bones look the same as the ones listed here. These are the parts of the file.
As most files, also the HRC files have got a kind of header. That are the first three lines.
This seems to be a simple "ID". As far as I know, this is the first line in all HRCs...
This tells you the name of the skeleton, in our example "sd_yufi_sk".
Tells you how much bones are stored in this skeleton.
Every bone consist of 4 Lines, which look like this. Let's first take a look at the lines of the first bone:
First Line: ("hip")
This is the name of the current bone.
Second Line: ("root")
This is the name of the parent bone. The parent bone must be already listed above in the skeleton file,or it can be "root" (origin).
Third Line: ("2.9662")
That's the Length of the bone.
Fourth Line #1: ("0")
Fourth Line #2: ("1 ABJC")
Fourth Line #3: ("2 ABJC ABJD")
This line consist of 2 or more different values. First, there is a number telling many RSD files are aligned to this model. If it has no RSD File, the number is 0. If the number is 1, there is a string after the number telling you the name of the Resource Data File (RSD). The RSD file tells you which .p Model to use.
There may be even more than 2 RSD Files on 1 Bone, however this has yet be be seen.
There are no bone angles, just bone lengths. The HRC file only contains hierarchy data. To build a skeleton, animation files are required.