From 07df5d9a1dcadf2a103ae2c0cfc4520cd0f9fcd1 Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Sun, 4 Jan 2026 18:04:49 -0600
Subject: [PATCH] gltf: add parent node calculation

---
 gltf.hpp          | 12 +++++++-----
 gltf_instance.hpp | 11 +++++++++++
 render_cpp.py     | 12 +++++++++---
 tree.py           | 20 ++++++++++++++++++++
 4 files changed, 47 insertions(+), 8 deletions(-)
 create mode 100644 gltf_instance.hpp
 create mode 100644 tree.py

diff --git a/gltf.hpp b/gltf.hpp
index 5eb089e..deb9f69 100644
--- a/gltf.hpp
+++ b/gltf.hpp
@@ -1,3 +1,6 @@
+#ifndef GLTF_HPP_
+#define GLTF_HPP_
+
 struct Mesh {
   const D3DXVECTOR3 * position;
   const DWORD position_size;
@@ -21,6 +24,7 @@ struct Mesh {
 struct Skin;
 
 struct Node {
+  const DWORD parent_ix;
   const Skin * skin; // skin index (global)
   const Mesh * mesh; // mesh index (global)
   const D3DXVECTOR3 translation;
@@ -50,12 +54,10 @@ struct AnimationSampler {
 struct AnimationChannel {
   const AnimationSampler * sampler; // sampler index, this animation
   struct {
-    const Node * node; // node index
+    const int node_ix;
     const AnimationChannelPath path; // property to animate
   } target;
 };
 
-//struct Animation {
-//  const AnimationChannel * channels;
-//  const AnimationSampler * samplers;
-//};
+#ifndef GLTF_HPP_
+#define GLTF_HPP_
diff --git a/gltf_instance.hpp b/gltf_instance.hpp
new file mode 100644
index 0000000..2ae1f31
--- /dev/null
+++ b/gltf_instance.hpp
@@ -0,0 +1,11 @@
+#ifndef GLTF_INSTANCE_HPP_
+#define GLTF_INSTANCE_HPP_
+
+struct NodeInstance {
+  const Node * node;
+  D3DXVECTOR3 translation;
+  D3DXQUATERNION rotation;
+  D3DXVECTOR3 scale;
+};
+
+#endif
diff --git a/render_cpp.py b/render_cpp.py
index a1561eb..66f2ef8 100644
--- a/render_cpp.py
+++ b/render_cpp.py
@@ -6,8 +6,7 @@ from gltf import decode_file
 from gltf import validate_mesh
 from gltf import decode_accessor
 
-filename = sys.argv[1]
-gltf = decode_file(filename)
+from tree import build_tree
 
 def type_name(type):
     return {
@@ -101,6 +100,8 @@ def render_nodes(gltf):
         skin = node["skin"]
         yield f"extern const Skin skin_{skin};"
 
+    node_parents = build_tree(gltf)
+
     for node_ix, node in enumerate(gltf.json["nodes"]):
         skin = f"&skin_{node['skin']}" if "skin" in node else "NULL"
         mesh = f"&mesh_{node['skin']}" if "mesh" in node else "NULL"
@@ -115,7 +116,10 @@ def render_nodes(gltf):
         if "rotation" in node:
             rotation = node["rotation"]
 
+        parent_ix = node_parents.get(node_ix, -1)
+
         yield f"const Node node_{node_ix} = {{"
+        yield f"{parent_ix}, // parent_ix"
         yield f"{skin}, // skin"
         yield f"{mesh}, // mesh"
         yield f"{render_value(translation, 'D3DXVECTOR3')}, // translation"
@@ -155,7 +159,7 @@ def render_animation_channels(animation_ix, channels):
         target_path = channel["target"]["path"]
         yield f"&animation_{animation_ix}__sampler_{sampler}, // animation sampler"
         yield "{"
-        yield f"&node_{target_node}, // target node"
+        yield f"{target_node}, // target node index"
         yield f"ACP__{target_path.upper()}, // target path"
         yield "},"
     yield "};"
@@ -172,6 +176,8 @@ def render_gltf(gltf):
     yield from render_skins(gltf)
     yield from render_animations(gltf)
 
+filename = sys.argv[1]
+gltf = decode_file(filename)
 render, out = renderer()
 render(render_gltf(gltf))
 print(out.getvalue())
diff --git a/tree.py b/tree.py
new file mode 100644
index 0000000..a963311
--- /dev/null
+++ b/tree.py
@@ -0,0 +1,20 @@
+from gltf import decode_file
+
+def build_tree(gltf):
+    parents = {} # from child to parent
+
+    for node_ix, node in enumerate(gltf.json["nodes"]):
+        if "children" not in node:
+            continue
+        for child_ix in node["children"]:
+            assert child_ix > node_ix, (child_ix, node_ix)
+            assert child_ix not in parents
+            parents[child_ix] = node_ix
+
+    return parents
+
+if __name__ == "__main__":
+    import sys
+    filename = sys.argv[1]
+    gltf = decode_file(filename)
+    build_tree(gltf)