Fix a transform update issue.

samples/03_model_render/model_loader.cpp

@@ -542,14 +542,14 @@ ModelLoader::LoadModel(cstr path, cstr name, bool batched)
                 const mat4 transform =
                     translate(mat4(1.0f), nodeTranslation) * mat4_cast(nodeRotation) * scale(mat4(1.0f), nodeScale) * nodeMatrix;
 
-                const u32 nodeArrayIndex = nodes.Add(transform, parent);
+                const i32 nodeArrayIndex = Cast<i32>(nodes.Add(transform, parent));
                 if (node->mesh >= 0)
                 {
                     auto [start, count] = meshPrimRanges[node->mesh];
                     const auto end = start + count;
                     for (usize i = start; i != end; ++i)
                     {
-                        meshPrimitives[i].m_TransformIdx = Cast<i32>(nodeArrayIndex);
+                        meshPrimitives[i].m_TransformIdx = nodeArrayIndex;
                     }
                 }
 
@@ -711,7 +711,7 @@ Model::operator=(Model &&other) noexcept
     m_NormalHandle = other.m_NormalHandle;
     m_TexCoord0Handle = other.m_TexCoord0Handle;
     m_VertexColorHandle = other.m_VertexColorHandle;
-    m_NodeHandle = std::move(other.m_NodeHandle);
+    m_NodeHandle = other.m_NodeHandle;
     m_IndexBuffer = other.m_IndexBuffer;
     m_MeshPrimitives = std::move(other.m_MeshPrimitives);
     return *this;

samples/03_model_render/model_loader.h

@@ -34,6 +34,7 @@ struct Nodes
 {
     eastl::vector<mat4> m_Transforms;
     eastl::vector<mat4> m_GlobalTransforms;
+    /// Parents are also used for bookkeeping
     eastl::vector<u32> m_Parents_;
     bool m_Dirty = true;
 
@@ -42,10 +43,10 @@ struct Nodes
     constexpr static u32 PARENT_MASK = ~(ROOT_BIT | DIRTY_BIT);
 
     u32
-    Add(const mat4& transform, i32 parent = -1)
+    Add(const mat4& transform, const i32 parent = -1)
     {
         m_Dirty = true;
-        u32 index = Count();
+        const u32 index = Count();
         m_Transforms.push_back(transform);
         m_GlobalTransforms.push_back(transform);
         const u32 parentVal = (parent < 0 ? ROOT_BIT : parent & PARENT_MASK) | DIRTY_BIT;
@@ -113,22 +114,39 @@ struct Nodes
 
         while (parentIter != parentEnd)
         {
-            if (!(*parentIter & ROOT_BIT) && *parentIter & DIRTY_BIT)
+            const bool isRoot = *parentIter & ROOT_BIT;
+            const bool isDirty = *parentIter & DIRTY_BIT;
+
+            if (isRoot)
             {
-                u32 parent = *parentIter & PARENT_MASK;
-                *globalTransformIter = m_GlobalTransforms[parent] * *transformIter;
+                if (isDirty)
+                {
+                    // Copy-update if the root is dirty.
+                    *globalTransformIter = *transformIter;
+                }
             }
             else
             {
-                *globalTransformIter = *transformIter;
+                const u32 parentIdx = *parentIter & PARENT_MASK;
+                const bool isParentDirty = m_Parents_[parentIdx] & DIRTY_BIT;
+                if (isDirty || isParentDirty)
+                {
+                    // Update w.r.t parent if either local or parent transforms updated.
+                    *globalTransformIter = m_GlobalTransforms[parentIdx] * *transformIter;
+                    m_Parents_[parentIdx] |= m_Dirty;       // Set dirty to propagate the update.
+                }
             }
-            *parentIter &= ~DIRTY_BIT;
 
             ++parentIter;
             ++globalTransformIter;
             ++transformIter;
         }
 
+        for (u32 &parentValue : m_Parents_)
+        {
+            parentValue &= ~DIRTY_BIT;  // Unset dirty.
+        }
+
         m_Dirty = false;
     }
 };