From cf5e85c57ac8f69ffdf599e0c14aa6a8ec304184 Mon Sep 17 00:00:00 2001
From: metamuffin <metamuffin@disroot.org>
Date: Sat, 22 Feb 2025 20:46:47 +0100
Subject: inverse bind mats

---
 doc/resources.md        | 11 ++++++-----
 shared/src/resources.rs |  1 +
 world/src/main.rs       | 14 ++++++++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/doc/resources.md b/doc/resources.md
index 761a6fa..7d06e71 100644
--- a/doc/resources.md
+++ b/doc/resources.md
@@ -125,11 +125,12 @@ Armature is used for humanoid avatar rigging and generally follows VRM
 specification. Joints are arranged in a hierarchy where transforms are
 inherited. Attribute values are zipped similar to vertex attributes.
 
-| Key         | Value Type  |                                        |
-| ----------- | ----------- | -------------------------------------- |
-| `parent`    | `[u16]`     | Parent indecies, Root points to itself |
-| `transform` | `[Affine3]` |                                        |
-| `name`      | `[String]`  | Each string prefixed with u16 length   |
+| Key              | Value Type  |                                        |
+| ---------------- | ----------- | -------------------------------------- |
+| `parent`         | `[u16]`     | Parent indecies, Root points to itself |
+| `transform`      | `[Affine3]` |                                        |
+| `rest_transform` | `[Affine3]` |                                        |
+| `name`           | `[String]`  | Each string prefixed with u16 length   |
 
 - **Names**: Indirectly controlled joints have an empty name. All other bones
   are named like in [VRMC_vrm].
diff --git a/shared/src/resources.rs b/shared/src/resources.rs
index 4460feb..f502485 100644
--- a/shared/src/resources.rs
+++ b/shared/src/resources.rs
@@ -179,6 +179,7 @@ resource_dicts!(
     pub struct ArmaturePart {
         parent: Vec<u16>,
         transform: Vec<Affine3A>,
+        rest_transform: Vec<Affine3A>,
         name: Vec<String>,
     }
 
diff --git a/world/src/main.rs b/world/src/main.rs
index a56ea74..16ed941 100644
--- a/world/src/main.rs
+++ b/world/src/main.rs
@@ -170,9 +170,18 @@ fn main() -> Result<()> {
             let mut name = Vec::new();
             let mut parent_pre_map = Vec::new();
             let mut transform = Vec::new();
+            let mut rest = Vec::new();
 
             for skin in gltf.skins() {
+                let mut inverse_bind_mat = skin
+                    .reader(|buf| Some(&buffers[buf.index()]))
+                    .read_inverse_bind_matrices();
                 for (j_ind, j) in skin.joints().enumerate() {
+                    let ibm = if let Some(x) = &mut inverse_bind_mat {
+                        Some(x.next().unwrap())
+                    } else {
+                        None
+                    };
                     let a_ind = match joint_index_to_arm_index.get(&j.index()) {
                         Some(i) => *i,
                         None => {
@@ -185,6 +194,10 @@ fn main() -> Result<()> {
                                     .find(|n| n.children().any(|c| c.index() == j.index()))
                                     .map(|n| n.index()),
                             );
+                            rest.push(
+                                ibm.map(|a| transform_to_affine(Transform::Matrix { matrix: a }))
+                                    .unwrap_or(Affine3A::IDENTITY),
+                            );
 
                             joint_index_to_arm_index.insert(j.index(), a_ind);
                             a_ind
@@ -218,6 +231,7 @@ fn main() -> Result<()> {
                 name: Some(name),
                 parent: Some(parent),
                 transform: Some(transform),
+                rest_transform: Some(rest),
             }
         };
 
-- 
cgit v1.2.3-70-g09d2