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Cleanup: better documentation for the Bone struct

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Improve the documentation for the Bone coordinate spaces and these struct fields:

- `head` & `tail`
- `bone_mat`
- `arm_head` / `arm_tail`
- `dist`

No functional changes.

Pull Request: https://projects.blender.org/blender/blender/pulls/143729
This commit is contained in:
Sybren A. Stüvel
2025-08-21 14:10:25 +02:00
parent bca70c85e7
commit a7cf8963da
1 changed files with 26 additions and 11 deletions
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37
source/blender/makesdna/DNA_armature_types.h
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@@ -27,12 +27,20 @@ class BoneColor;
struct AnimData;
struct BoneCollection;
/* this system works on different transformation space levels;
/* The Armature system works on different transformation space levels:
*
* 1) Bone Space; with each Bone having its own (0,0,0) origin
* 2) Armature Space; the rest position, in Object space, Bones Spaces are applied hierarchical
* 3) Pose Space; the animation position, in Object space
* 4) World Space; Object matrix applied to Pose or Armature space
* 1) Bone Space: In the orientation of the parent bone, position relative
* to the parent's tail. Same as Armature Space for bones
* without parent.
* 2) Armature Space: The bone's rest transform in Object space. This is the
* multiplication of the bone space matrices of the bone and
* all its ancestors.
* 3) Pose Space: The bone's posed transform in Object space. This is the
* same space as Armature Space, except that it represents
* the current bone transform instead of the rest pose.
* See bPoseChannel::pose_mat
* 4) Channel Space: The bone's local transform relative to its rest transform.
* See bPoseChannel::chan_mat
*/
typedef struct BoneColor {
@@ -73,10 +81,14 @@ typedef struct Bone {
/** Roll is input for edit-mode, length calculated. */
float roll;
/** Head position in Bone Space (see top of this file). */
float head[3];
/** Head/tail and roll in Bone Space. */
/** Tail position in Bone Space (see top of this file). */
float tail[3];
/** Rotation derived from head/tail/roll. */
/**
* Bone matrix in Bone Space (see top of this file).
*
* bone.matrix in RNA. Computed in BKE_armature_where_is_bone(). */
float bone_mat[3][3];
int flag;
@@ -87,16 +99,19 @@ typedef struct Bone {
char inherit_scale_mode;
char _pad[3];
/** Head position in armature space. So should be the same as head in edit mode. */
float arm_head[3];
/** Head/tail in Armature Space (rest pose). */
/** Tail position in armature space. So should be the same as tail in edit mode. */
float arm_tail[3];
/** Matrix: `(bonemat(b)+head(b))*arm_mat(b-1)`, rest pose. */
/** Matrix: `(bone_mat(b)+head(b))*arm_mat(b-1)`, rest pose in armature space. */
float arm_mat[4][4];
/** Roll in Armature Space (rest pose). */
float arm_roll;
/** dist, weight: for non-deformgroup deforms. */
float dist, weight;
/** Envelope distance, added to rad_head / rad_tail. */
float dist;
/** Weight: for non-deformgroup deforms. */
float weight;
/**
* The width for block bones. The final X/Z bone widths are double these values.
*