feat(vfx): bind effects to live animated poses

src/AcDream.App/Rendering/Vfx/IndexedSetupPartPoseBuilder.cs

@@ -0,0 +1,66 @@
+using System.Numerics;
+using AcDream.Core.Meshing;
+using AcDream.Core.World;
+using DatReaderWriter.DBObjs;
+
+namespace AcDream.App.Rendering.Vfx;
+
+/// <summary>
+/// Reconstructs retail's stable CPartArray indices from a drawable-only
+/// MeshRef projection. Rigid part frames come from Setup data while missing
+/// DAT parts keep an unavailable placeholder at their stable Setup index.
+/// Hydration omits by GfxObj DID and otherwise preserves Setup order, so
+/// duplicate DIDs are all present or all absent; first-unconsumed matching is
+/// lossless under that invariant.
+/// </summary>
+internal static class IndexedSetupPartPoseBuilder
+{
+    public static (Matrix4x4[] Poses, bool[] Available) Build(
+        Setup setup,
+        WorldEntity entity)
+    {
+        ArgumentNullException.ThrowIfNull(setup);
+        ArgumentNullException.ThrowIfNull(entity);
+
+        int partCount = setup.Parts.Count;
+        var poses = new Matrix4x4[partCount];
+        IReadOnlyList<Matrix4x4> defaults = SetupPartTransforms.Compute(
+            setup,
+            objectScale: entity.Scale);
+        for (int i = 0; i < partCount; i++)
+            poses[i] = i < defaults.Count ? defaults[i] : Matrix4x4.Identity;
+
+        var expectedGfx = new uint[partCount];
+        for (int i = 0; i < partCount; i++)
+            expectedGfx[i] = (uint)setup.Parts[i];
+        for (int i = 0; i < entity.PartOverrides.Count; i++)
+        {
+            PartOverride replacement = entity.PartOverrides[i];
+            if (replacement.PartIndex < expectedGfx.Length)
+                expectedGfx[replacement.PartIndex] = replacement.GfxObjId;
+        }
+
+        var available = new bool[partCount];
+        var consumed = new bool[entity.MeshRefs.Count];
+        for (int partIndex = 0; partIndex < partCount; partIndex++)
+        {
+            for (int drawableIndex = 0; drawableIndex < entity.MeshRefs.Count; drawableIndex++)
+            {
+                if (consumed[drawableIndex]
+                    || entity.MeshRefs[drawableIndex].GfxObjId != expectedGfx[partIndex])
+                {
+                    continue;
+                }
+
+                consumed[drawableIndex] = true;
+                available[partIndex] = true;
+                // The drawable transform carries DefaultScale. Retail's
+                // attachment/effect frame is the rigid Setup frame computed
+                // above; matching only establishes which stable slot exists.
+                break;
+            }
+        }
+
+        return (poses, available);
+    }
+}