Unofficial MDC Format Specification

Notes:

Container object. References to all MDC data.

Notes:

General information about MDC data. Used mainly to navigate file data.

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Describes bounding volume information: axially aligned bounding box and bounding sphere.

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General information about a tag.

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A tag in a specific frame.

To convert location and orientation values to float, a scale value is used.

Orientation values are given as euler angles. Inside file they are stored in order of pitch, yaw, roll. Rotation order is: first roll, then pitch, then yaw (XYZ, intrinsic).

Additionally, orientation values should be in range of [-32700, 32700], since the hardcoded scale value is 360/32700. TODO value ranges, normalized.

Background:

Tags are used to attach external models to a model. Attachment means that the external models origin aligns itself with the models tag location and orientation. As the external model is parented to the tag (nested in tag space), any animation of the tag will also affect the external model.

Domain specific scripts tell the engine which external models to attach to a given tag. These scripts are either located in mapscript files (attachtotag command) or .skin files. Sometimes they are also hard coded.

An example use case is a hat model (defined separately) attached to a head model. This way, characters can be assembled with different looks without having to duplicate their model definitions. Tags therefore support reuse.

Another example use case is that of a tank turret model attached to a tank model. Instead of having a shooting animation (rotate turret left, shoot, rotate turret right) be recorded as vertex positions across several key-frames inside a single model, a tag can be used to control the shooting animation of a separated model. This safes memory, as the tags animation data most likely takes much less space compared to the animation data of the tank turret inside a single model.

However, reuse and memory savings are traded against loss in performance. Vertex positions of the external models have to be recalculated against the current frame tags location and orientation.

Notes:

Container object. References surface data.

Background:

Surfaces are described by geometry, color and animation data. A model can consist of multiple surfaces.

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General information about a surface. Used mainly to navigate surface data.

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A triangle for a surface.

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Shader for a surface. The name of the shader is a reference to either a shader inside a script file, or a path from top level directory to an texture image. Suffixes like .tga or .jpg can be omitted. Search order is: shader, .tga, .jpg. First found will be used.

Background:

Shaders manipulate surface properties. These properties define how the surface interacts with light sources present in a scene.

The term can be a bit confusing, since a shader in this context can either mean a script file (with references to texture images) or an texture image.

Notes:

Texture coordinates for a single vertex. UV coordinates are given so that u points right, and v points down. Each value should be in range of [0, 1]. Values outside this range are interpreted as repeating. Each vertex is mapped exactly once to UV-space. Therefore, seams will most likely cause an exporter to add additional vertices along the seam line to enforce bijection. UV-maps are stored once per surface.

Background:

The UV-map is used to color the surface with solid color from a 2D image. Texture coordinates make up UV-space.

Notes:

Vertex location and normal in a base frame. Each key frame contains a list of vertex locations and normals. Base frames contain the base vertex values to which offset values from compressed frames are added. Base frame indices are encoded in the list of MDCBaseFrameIndices.

Vertex location values from file are given as compressed 16-Bit integers. To convert this range to a range of floats, the given value is linearly mapped. For this, a hard coded scale value is used.

Vertex normals manipulate the shading of a surface (for example smooth or flat). They are given in spherical coordinates. Since the coordinates describe the direction of a normal, the radius value is omitted and only latitude and longitude values are given as unsigned 8-bit values from file. To convert them to cartesian space, the upwards vector is first rotated by the latitude value, then by the longitude value. Latitude range is within [0, 180] degrees. Longitude range is within [0, 360) degrees. To obtain the values in degrees, the given range of [0, 255] from file needs to be linearly mapped to [0, 360) degrees.

Notes:

Vertex location and normal in a compressed frame. Each key frame contains a list of vertex locations and normals. Compressed frames contain offset values which are added to their respective base frame. The base frame for a compressed frame is encoded in the list of MDCBaseFrameIndices.

Vertex location values from file are given as compressed 8-Bit integers. To convert this range to a range of floats, the given value is linearly mapped. For this, a hard coded scale value is used.

Vertex normals manipulate the shading of a surface (for example smooth or flat). They are given as an index into a list of precalculated normals.

Notes:

Indices into the list of base frame vertices.

Surfaces hold two seperate lists to store the vertex coordinates either as base or compressed. The indices are used to retrieve the index into the list of base frames for a specific frame.

Notes:

Indices into the list of compressed frame vertices.

Surfaces hold two seperate lists to store the vertex coordinates either as base or compressed. The indices are used to retrieve the index into the list of compressed frames for a specific frame. If a frame is not compressed, the retrieved value will be -1.