Skin PLG (RW Section)
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| Skin PLG | |
|---|---|
| RenderWare Stream Section | |
| Vendor | Criterion Games |
| Module | Toolkit |
| Module ID | 0x000001
|
| Identifier | 0x16
|
| Chunk ID | 0x00000116
|
| Versions | All |
| Hierarchy | |
| Parents: Geometry (Extension) | |
| Children: None | |
| Extensions: None | |
| File Format | |
Skin is an additional RenderWare plugin for geometry section. It is used to hold information about skinned model.
Structure
The structure starts with a 4-byte value, where each individual byte contains a counter and the last byte being used for padding.
1b - BYTE - numBones: Overall number of bones in the skeleton. 1b - BYTE - usedBones: Number of bones affected by the skin. 1b - BYTE - maxVertexWeights: Maximum number of non-zero weights per vertex. 1b - BYTE - Padding
The third counter can be any value from 0 to 4. If it equals zero, the engine attempts to figure out this number by looking into each weight array (see below) and counting the non-zero weights. It then takes the largest number from the results.
The counters are followed by multiple arrays that contain information about how vertices of a mesh relate to bones. The number of vertices is obtained from the parent geometry section.
Xb - BYTE[usedBones] - A list of bone indices, that are affected by the skin. Xb - BYTE[numVertices][4] - A list that maps all vertices to (up to) four bones of the skeleton. Xb - FLOAT[numVertices] - A list that weights each vertex-bone mapping.
Next, a list of transformation matrices for each bone is provided:
Xb - Bone[numBones] - Bone transformations
Where Bone is defined as follows:
struct Bone {
DWORD unused; // Only stored if version < 0x37000 && maxVertexWeights == 0
FLOAT transform[4][4]; // Skin-to-Bone transform.
};Bone Group Remapping
As indicated above by the usedBones counter, a mesh (stored within the parent geometry) may not affected by all bones in the skeleton. Some platforms only support a certain number of bones at once. Thus RenderWare can split up a skeleton into groups, where group-indices must be mapped to the actual bone indices. Those groups are stored in a run-length encoded fashion.
For all RenderWare-based GTA games, this feature is typically unused. Thus the following values are usually set to zero.
4b - DWORD - boneLimit: the maximum number of bones per group. (?) 4b - DWORD - numGroups: the number of bone groups. 4b - DWORD - numRemaps: the number of bone remappings.
If there are any groups (numGroups > 0), the counters are followed by three arrays:
Xb - BYTE[numBones] - boneRemapIndices: an array of all bone indices where each element identifies a bone of the skeleton Xb - BoneGroup[numGroups] - boneGroups (see below) Xb - BoneRemap[numRemaps] - boneRemaps (see below)
Where BoneGroup and BoneRemap is defined as follows:
struct BoneGroup {
BYTE firstBone; // Index of first bone in boneRemaps array.
BYTE numBones; // Number of bones in boneRemaps that define the mesh (starting from firstBone).
};
struct BoneRemap {
BYTE boneIndex; // Index of the bone in boneRemapIndices.
BYTE indices; // The number of elements of the boneRemapIndices that are included by the group in boneRemapIndices.
};
