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Tokei

RSM2 file format!

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Heya,

This post is meant to explain the file format of RSM2 for those who are interested and want to play with them. I haven't seen many projects exploring the topic and I've finished digging through the file for GRF Editor. I shared some of the structure pubicly in BrowEdit's Discord almost a year ago, but the fields were still unknown at that point. Also before anyone asks, no I am not making a public converter for RSM2 > RSM1. That's not fully possible anyway.

General
The structure of a RSM file is quite simple. It's a list of mesh data with transformations applied to them. Each mesh has a transformation matrix, a position, a parent, etc. Then you have the transformation components on the mesh:

  • Offset/Translation
  • RotationAngle
  • RotationAxis
  • Scale

And at last, you have the animation components on the mesh:

  • RotationKeyFrame
  • ScaleKeyFrame

All the code presented below comes from GRF Editor. Also the structure varies quite a bit even among the 2.2 version and the 2.3 version. I was unable to find any model using versions 2.0 or 2.1. I'd guess they were only used internally...? Who knows.

Animation duration changes
In previous versions, below 2.2, the AnimationLength field and the frame animation field represented time in milliseconds. So a model such as ps_h_01.rsm has 48000 as a value for AnimationLength, which means the animation lasts for a whole 48 seconds before it resets. The key frames for the transformations work in the same manner.

In version 2.2 and above, the AnimationLength field reprensents the total amount of frames in the model. So a model such as reserch_j_01.rsm2 has a value of 300. The keyframes would therefore range between 0 and 300. The duration is given by the new FramesPerSecond field, which is 30 for almost all 2.0 models currently existing. The delay between frames would then be 1000 / FramesPerSecond = 33.33 ms. The duration would be 1000 / FramesPerSecond * AnimationLength = 1000 / 30 * 300 = 10000 ms in our example.

Shading
Nothing new there, but I thought I'd go over the topic quickly. The ShadeType property is used to calculate the normals. There are three types that have been found in models to this day:

  • 0: none; the normals are all set to (-1, -1, -1).
  • 1: flat; normals are calculated per triangle, with a typical cross product of the 3 vertices.
  • 2: smooth; each face of a mesh belongs to a smooth group, the normal is then calculated by adding the face normal of each connected vertices.

In the real world, most models end up using the smooth shading type. The smooth group is a bit confusing at first if you've never heard of it, but some reading on the topic will help you. These are common techniques.

Textures
In previous versions, below 2.3, the textures were defined at the start of the file. Each mesh then defines a list of indices. So for example, a mesh could define these indices: "2, 5, 0" which means the mesh has 3 textures. Each face of the mesh then has a TextureId property from 0 to 2 in our example. If the face TextureId is 1, it would refer to the second indice previously defined, which is 5. This means that the texture used for this face would be the 5th texture defined at the start of the model.

In version 2.3 and above, the textures are defined per mesh instead. There are no longer using texture indices. The TextureId defined for each face refers directly to the texture defined of that particular mesh. So say the TextureId for a face is 1, then the first texture defined on the mesh is the corresponding one.

Transformation order
In version 2.2 and above, the Scale/Offset/RotationAngle/RotationAxis properties were removed. Instead, it relies on animation frames or the TransformationMatrix. 

The order looks as such:

/// <summary>
/// Calculates the MeshMatrix and MeshMatrixSelf for the specified animation frame.
/// </summary>
/// <param name="animationFrame">The animation frame.</param>
public void Calc(int animationFrame) {
	MeshMatrixSelf = Matrix4.Identity;
	MeshMatrix = Matrix4.Identity;

	// Calculate Matrix applied on the mesh itself
	if (ScaleKeyFrames.Count > 0) {
		MeshMatrix = Matrix4.Scale(MeshMatrix, GetScale(animationFrame));
	}

	if (RotationKeyFrames.Count > 0) {
		MeshMatrix = Matrix4.Rotate(MeshMatrix, GetRotationQuaternion(animationFrame));
	}
	else {
		MeshMatrix = Matrix4.Multiply2(MeshMatrix, new Matrix4(TransformationMatrix));

		if (Parent != null) {
			MeshMatrix = Matrix4.Multiply2(MeshMatrix, new Matrix4(Parent.TransformationMatrix).Invert());
		}
	}

	MeshMatrixSelf = new Matrix4(MeshMatrix);
	
	Vertex position;

	// Calculate the position of the mesh from its parent
	if (PosKeyFrames.Count > 0) {
		position = GetPosition(animationFrame);
	}
	else {
		if (Parent != null) {
			position = Position - Parent.Position;
			position = Matrix4.Multiply2(new Matrix4(Parent.TransformationMatrix).Invert(), position);
		}
		else {
			position = Position;
		}
	}

	MeshMatrixSelf.Offset = position;

	// Apply parent transformations
	Mesh mesh = this;

	while (mesh.Parent != null) {
		mesh = mesh.Parent;
		MeshMatrixSelf = Matrix4.Multiply2(MeshMatrixSelf, mesh.MeshMatrix);
	}

	// Set the final position relative to the parent's position
	if (Parent != null) {
		MeshMatrixSelf.Offset += Parent.MeshMatrixSelf.Offset;
	}

	// Calculate children
	foreach (var child in Children) {
		child.Calc(animationFrame);
	}
}

The original vertices are then multiplied by MeshMatrixSelf for their final positions. MeshMatrix is the resulting transformation matrix of a particular mesh only, without taking into account its parents matrixes or the mesh position. The MeshMatrixSelf is the final transformation matrix that will be applied to the vertices. Contrary to previous versions, the TransformationMatrix is applied all the way to the children. The matrix invert function may not be available in all common librairies, so here is the implementation used:

public Matrix4 Invert() {
	if (this.IsDistinguishedIdentity)
		return this;
	if (this.IsAffine)
		return this.NormalizedAffineInvert();
	float num1 = this[2] * this[7] - this[6] * this[3];
	float num2 = this[2] * this[11] - this[10] * this[3];
	float num3 = this[2] * this[15] - this[14] * this[3];
	float num4 = this[6] * this[11] - this[10] * this[7];
	float num5 = this[6] * this[15] - this[14] * this[7];
	float num6 = this[10] * this[15] - this[14] * this[11];
	float num7 = this[5] * num2 - this[9] * num1 - this[1] * num4;
	float num8 = this[1] * num5 - this[5] * num3 + this[13] * num1;
	float num9 = this[9] * num3 - this[13] * num2 - this[1] * num6;
	float num10 = this[5] * num6 - this[9] * num5 + this[13] * num4;
	float num11 = this[12] * num7 + this[8] * num8 + this[4] * num9 + this[0] * num10;
	if (IsZero(num11))
		return false;
	float num12 = this[0] * num4 - this[4] * num2 + this[8] * num1;
	float num13 = this[4] * num3 - this[12] * num1 - this[0] * num5;
	float num14 = this[0] * num6 - this[8] * num3 + this[12] * num2;
	float num15 = this[8] * num5 - this[12] * num4 - this[4] * num6;
	float num16 = this[0] * this[5] - this[4] * this[1];
	float num17 = this[0] * this[9] - this[8] * this[1];
	float num18 = this[0] * this[13] - this[12] * this[1];
	float num19 = this[4] * this[9] - this[8] * this[5];
	float num20 = this[4] * this[13] - this[12] * this[5];
	float num21 = this[8] * this[13] - this[12] * this[9];
	float num22 = this[2] * num19 - this[6] * num17 + this[10] * num16;
	float num23 = this[6] * num18 - this[14] * num16 - this[2] * num20;
	float num24 = this[2] * num21 - this[10] * num18 + this[14] * num17;
	float num25 = this[10] * num20 - this[14] * num19 - this[6] * num21;
	float num26 = this[7] * num17 - this[11] * num16 - this[3] * num19;
	float num27 = this[3] * num20 - this[7] * num18 + this[15] * num16;
	float num28 = this[11] * num18 - this[15] * num17 - this[3] * num21;
	float num29 = this[7] * num21 - this[11] * num20 + this[15] * num19;
	float num30 = 1.0f / num11;
	this[0] = num10 * num30;
	this[1] = num9 * num30;
	this[2] = num8 * num30;
	this[3] = num7 * num30;
	this[4] = num15 * num30;
	this[5] = num14 * num30;
	this[6] = num13 * num30;
	this[7] = num12 * num30;
	this[8] = num29 * num30;
	this[9] = num28 * num30;
	this[10] = num27 * num30;
	this[11] = num26 * num30;
	this[12] = num25 * num30;
	this[13] = num24 * num30;
	this[14] = num23 * num30;
	this[15] = num22 * num30;
	return this;
}

New transformation animations

  • TranslationKeyFrames
    • In version 2.2 and above, PosKeyFrames are added. If you've seen the previous formats, you may be confused by this. I've seen PosKeyFrames in many implementations, but version 1.6 adds ScaleKeyFrames, not TranslationKeyFrames. The name is self-explanatory: it translates the mesh.
  • TextureKeyFrames
    • In version 2.3 and above, TextureKeyFrames are added. Similar to other transformations, they are defined as:
      struct TextureKeyFrame {
      	public int Frame;
      	public float Offset;
      }

       

The TextureKeyFrames target a specific texture ID from the mesh and have different animation types. The Offset affects the UV offsets of the textures. The animation types are:

  • 0: Texture translation on the X axis. The texture is tiled.
  • 1: Texture translation on the Y axis. The texture is tiled.
  • 2: Texture multiplication on the X axis. The texture is tiled.
  • 3: Texture multiplication on the Y axis. The texture is tiled.
  • 4: Texture rotation around (0, 0). The texture is not tiled.

Main mesh
In previous versions, below 2.2, there could only be one root mesh. This is no longer the case with newer versions.

Code
And those were all the changes! Here is a full description of the structure (which is again based on GRF Editor).

#
#  RSM structure
#
private Rsm(IBinaryReader reader) {
	int count;
	
	// The magic of RMS files is always GRSM
	Magic = reader.StringANSI(4);
	
	MajorVersion = reader.Byte();
	MinorVersion = reader.Byte();
	
	// Simply converting the version to a more readable format
	Version = FormatConverters.DoubleConverter(MajorVersion + "." + MinorVersion);
	
	// See "Animation duration changes" above for more information.
	AnimationLength = reader.Int32();
	ShadeType = reader.Int32();
	Alpha = 0xFF;
	
	// Apparently this is the alpha value of the mesh... but it has no impact in-game, so...
	if (Version >= 1.4) {
		Alpha = reader.Byte();
	}
	
	if (Version >= 2.3) {
		FrameRatePerSecond = reader.Float();
		count = reader.Int32();
		
		// In the new format, strings are now written with their length as an integer, then the string. In previous versions, strings used to be 40 in length with a null-terminator.
		// The syntax below may be a bit confusing at first.
		// reader.Int32() reads the length of the string.
		// reader.String(int) reads a string with the specific length.
		for (int i = 0; i < count; i++) {
			MainMeshNames.Add(reader.String(reader.Int32()));
		}
		
		count = reader.Int32();
	}
	else if (Version >= 2.2) {
		FrameRatePerSecond = reader.Float();
		int numberOfTextures = reader.Int32();
		
		for (int i = 0; i < numberOfTextures; i++) {
			_textures.Add(reader.String(reader.Int32()));
		}
		
		count = reader.Int32();
		
		for (int i = 0; i < count; i++) {
			MainMeshNames.Add(reader.String(reader.Int32()));
		}
		
		count = reader.Int32();
	}
	else {
		// Still unknown, always appears to be 0 though.
		Reserved = reader.Bytes(16);
		count = reader.Int32();
		
		for (int i = 0; i < count; i++) {
			_textures.Add(reader.String(40, '\0'));
		}
		
		MainMeshNames.Add(reader.String(40, '\0'));
		count = reader.Int32();
	}
	
	// The Mesh structure is defined below
	for (int i = 0; i < count; i++) {
		_meshes.Add(new Mesh(reader, Version));
	}
	
	// The rest of the structure is a bit sketchy. While this is apparently what it should be (some models do indeed have those), they have absolutely no impact in-game and can be safely ignored when rendering the model.
	if (Version < 1.6) {
		count = reader.Int32();
		
		for (int i = 0; i < count; i++) {
			_scaleKeyFrames.Add(new ScaleKeyFrame {
				Frame = reader.Int32(),
				Sx = reader.Float(),
				Sy = reader.Float(),
				Sz = reader.Float(),
				Data = reader.Float()
			});
		}
	}
	
	count = reader.Int32();
	
	for (int i = 0; i < count; i++) {
		VolumeBoxes.Add(new VolumeBox() {
			Size = new Vertex(reader.Float(), reader.Float(), reader.Float()),
			Position = new Vertex(reader.Float(), reader.Float(), reader.Float()),
			Rotation = new Vertex(reader.Float(), reader.Float(), reader.Float()),
			Flag = version >= 1.3 ? reader.Int32() : 0,
		});
	}
}

#
#  Mesh structure
#
public Mesh(IBinaryReader reader, double version) {
	int count;

	if (version >= 2.2) {
		Name = reader.String(reader.Int32());
		ParentName = reader.String(reader.Int32());
	}
	else {
		Name = reader.String(40, '\0');
		ParentName = reader.String(40, '\0');
	}

	if (version >= 2.3) {
		count = reader.Int32();

		for (int i = 0; i < count; i++) {
			Textures.Add(reader.String(reader.Int32()));
		}

		// This is more so for backward compatibility than anything. The texture indices now refer to the texture list of the mesh directly.
		for (int i = 0; i < count; i++) {
			_textureIndexes.Add(i);
		}
	}
	else {
		count = reader.Int32();

		for (int i = 0; i < count; i++) {
			_textureIndexes.Add(reader.Int32());
		}
	}

	// The TransformationMatrix is 3x3 instead of 4x4 like everything else in the universe.
	TransformationMatrix = new Matrix3(
		reader.Float(), reader.Float(), reader.Float(), 
		reader.Float(), reader.Float(), reader.Float(), 
		reader.Float(), reader.Float(), reader.Float());


	if (version >= 2.2) {
		// In 2.2, the transformations are already applied to the mesh, or calculated from the animation key frames. None of these properties are used anymore.
		Offset = new Vertex(0, 0, 0);
		Position = new Vertex(reader);
		RotationAngle = 0;
		RotationAxis = new Vertex(0, 0, 0);
		Scale = new Vertex(1, 1, 1);
	}
	else {
		// The Offset is the translation vector for the mesh. translated > scaled > rotated >TransformationMatrix.
		Offset = new Vertex(reader.Float(), reader.Float(), reader.Float());
		
		// Position is the distance between the mesh and its parent.
		Position = new Vertex(reader.Float(), reader.Float(), reader.Float());
		RotationAngle = reader.Float();
		RotationAxis = new Vertex(reader.Float(), reader.Float(), reader.Float());
		Scale = new Vertex(reader.Float(), reader.Float(), reader.Float());
	}

	count = reader.Int32();

	for (int i = 0; i < count; i++) {
		_vertices.Add(new Vertex(reader.Float(), reader.Float(), reader.Float()));
	}

	count = reader.Int32();

	for (int i = 0; i < count; i++) {
		_tvertices.Add(new TextureVertex {
			Color = version >= 1.2 ? reader.UInt32() : 0xFFFFFFFF,
			U = reader.Float(),
			V = reader.Float()
		});
	}

	count = reader.Int32();

	// A face has changed a little in the new version. The SmoothGroup isn't only bound to the face itself, but can be bound to the vertex itself instead.
	for (int i = 0; i < count; i++) {
		Face face = new Face();
		int len = -1;

		if (version >= 2.2) {
			len = reader.Int32();
		}

		face.VertexIds = reader.ArrayUInt16(3);
		face.TextureVertexIds = reader.ArrayUInt16(3);
		face.TextureId = reader.UInt16();
		face.Padding = reader.UInt16();
		face.TwoSide = reader.Int32();

		if (version >= 1.2) {
			face.SmoothGroup[0] = face.SmoothGroup[1] = face.SmoothGroup[2] = reader.Int32();

			if (len > 24) {
				// It is unsure if this smooth group is applied to [2] or not if the length is 28. Hard to confirm.
				face.SmoothGroup[1] = reader.Int32();
			}

			if (len > 28) {
				face.SmoothGroup[2] = reader.Int32();
			}
		}

		_faces.Add(face);
	}

	// This was weirdly predicted to be in model version 1.6... which never existed? Either way, it is safe to set it as >= 1.6
	if (version >= 1.6) {
		count = reader.Int32();

		for (int i = 0; i < count; i++) {
			_scaleKeyFrames.Add(new ScaleKeyFrame {
				Frame = reader.Int32(),
				Sx = reader.Float(),
				Sy = reader.Float(),
				Sz = reader.Float(),
				Data = reader.Float()	// Useless, has in impact in-game
			});
		}
	}

	count = reader.Int32();

	for (int i = 0; i < count; i++) {
		_rotFrames.Add(new RotKeyFrame {
			Frame = reader.Int32(),
			// Qx, Qy, Qz, Qw
			Quaternion = new TkQuaternion(reader.Float(), reader.Float(), reader.Float(), reader.Float())
		});
	}

	if (version >= 2.2) {
		count = reader.Int32();

		for (int i = 0; i < count; i++) {
			_posKeyFrames.Add(new PosKeyFrame {
				Frame = reader.Int32(),
				X = reader.Float(),
				Y = reader.Float(),
				Z = reader.Float(),
				Data = reader.Int32()	// Useless, has in impact in-game
			});
		}
	}
	
	// Texture animations, look at "Textures" above for more information
	if (version >= 2.3) {
		count = reader.Int32();

		for (int i = 0; i < count; i++) {
			int textureId = reader.Int32();
			int amountTextureAnimations = reader.Int32();

			for (int j = 0; j < amountTextureAnimations; j++) {
				int type = reader.Int32();
				int amountFrames = reader.Int32();

				for (int k = 0; k < amountFrames; k++) {
					_textureKeyFrameGroup.AddTextureKeyFrame(textureId, type, new TextureKeyFrame {
						Frame = reader.Int32(),
						Offset = reader.Float()
					});
				}
			}
		}
	}
}

I'm also sharing the program I used to test the RSM2 files. It's a bit messy, but it does the job and might help someone. This testing program no longer has any purpose to me as it's been merged into GRF Editor already.

The provided model is the following (it contains all the new features of RSM2):

test.gif.4f825b0e9a7180ad7191a55116502429.gif

The chain on the right as well as the lights use these new texture animations. The red ball uses the translation key frames.

This test project can read any RSM or RSM2 file as well as save them (you can edit RSM/RSM2 models via source). Changing the header version to change the output file will cause issues depending on which version you go from and to. With that said, have fun...! One day I'll make GRF Editor sources public again, one day.

Edited by Tokei
  • Upvote 8
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