Code/HumanoidRetargeter/Core/Formats/Mmd/MmdAuxiliaryMotion.cs
Applies auxiliary motion from an MMD-format source scene onto a target rig for bones that are not already role-driven or excluded. It matches source and target bones by name (with encoded fallbacks), computes a median scale factor, filters by parent mapping and length tolerance, then for each frame transfers positional offset scaled and applies rotational delta relative to source rest pose.
Native Interop
using System.Numerics;
using HumanoidRetargeter.Core.Maths;
using HumanoidRetargeter.Core.Skeleton;
using HumanoidRetargeter.Core.Target;
using HumanoidRetargeter.Core.Mapping;
namespace HumanoidRetargeter.Core.Formats.Mmd;
using Vector3 = System.Numerics.Vector3;
internal static class MmdAuxiliaryMotion
{
internal static void Apply( SourceScene scene, TargetRig target, List<XForm[]> frames, int take )
{
if ( target.HelpersAreConstraintDriven )
return;
var source = scene.Skeleton;
var rig = target.Skeleton;
var matches = new Dictionary<int, int>();
var scales = new List<float>();
var encodedSource = source.Bones.ToDictionary( bone => MmdBoneNames.Encode( bone.Name ), bone => bone.Index,
StringComparer.OrdinalIgnoreCase );
for ( var t = 0; t < rig.Count; t++ )
{
var s = source.IndexOf( rig[ t ].Name );
if ( s < 0 && encodedSource.TryGetValue( rig[ t ].Name, out var encoded ) )
s = encoded;
if ( s < 0 )
continue;
matches[ t ] = s;
var sourceLength = source[ s ].RestLocal.Pos.Length();
if ( sourceLength > 0.1f && rig[ t ].RestLocal.Pos.Length() > 0.1f )
scales.Add( rig[ t ].RestLocal.Pos.Length() / sourceLength );
}
if ( scales.Count == 0 )
return;
scales.Sort();
var scale = scales[ scales.Count / 2 ];
var excluded = new HashSet<int>();
if ( target.BoneForRole( BoneRole.Hips ) is { } hips )
{
for ( var parent = hips; parent >= 0; parent = rig[ parent ].ParentIndex )
excluded.Add( parent );
}
foreach ( var (t, s) in matches )
{
if ( target.RoleOf( t ) is not null || excluded.Contains( t ) )
continue;
var sp = source[ s ].ParentIndex;
var tp = rig[ t ].ParentIndex;
if ( sp >= 0 && (tp < 0 || !matches.TryGetValue( tp, out var mappedParent ) || mappedParent != sp) )
continue;
var sourceRest = source[ s ].RestLocal;
var targetRest = rig[ t ].RestLocal;
if ( MathF.Abs( sourceRest.Pos.Length() * scale - targetRest.Pos.Length() ) > MathF.Max( 0.1f, targetRest.Pos.Length() * 0.05f ) )
continue;
for ( var frame = 0; frame < frames.Count; frame++ )
{
var value = scene.Clips[ take ].Frames[ frame ][ s ];
var delta = Quaternion.Inverse( sourceRest.Rot ) * value.Rot;
var solved = frames[ frame ][ t ];
frames[ frame ][ t ] = new XForm( solved.Pos + (value.Pos - sourceRest.Pos) * scale,
Quaternion.Normalize( solved.Rot * delta ) );
}
}
}
}