Common Structures¶

Canonical definitions for small, frequently reused data structures across DRS classes.
These structs are referenced by multiple classes such as CGeoMesh, CGeoSubset, and CGeoMaterial.

Face¶

A Face represents a triangle defined by three 16-bit vertex indices into a mesh’s vertices array.

Field	Type	Description
`i0`	`ushort`	Index of first vertex (0-based)
`i1`	`ushort`	Index of second vertex (0-based)
`i2`	`ushort`	Index of third vertex (0-based)

Notes - Each face always references exactly three vertices — only triangles are supported. - Because face indices are stored as ushort, both the vertex index and face count are constrained by 16-bit limits.

Limits¶

Constraint	Description
`vertex_count ≤ 65,535`	Maximum addressable vertex index (`ushort` limit)
`face_count ≤ 21,845`	Maximum number of triangles (`65,535 / 3 ≈ 21,845`) if fully packed
`index_count = face_count * 3`	Each face consumes three indices

Implications - A single mesh block can contain at most ~21 k triangles. - Larger objects must be split into multiple mesh chunks.

Vertex (Vector4)¶

A Vertex used by many classes is a 4D float vector where w is always 1.0.

Component	Type	Description
`x`	`float`	X coordinate
`y`	`float`	Y coordinate
`z`	`float`	Z coordinate
`w`	`float`	Always `1.0` (homogeneous coordinate)

Notes - The extra component w exists for alignment and homogeneous transform support. - Importers typically ignore w since it’s constant.

Vector3¶

A 3D point or direction, stored as three 32-bit floats (x, y, z).
Total size: 12 bytes.

Component	Type	Bytes	Notes
`x`	float	4	little-endian IEEE-754
`y`	float	4
`z`	float	4

Usage
Common across geometry and animation data (e.g., CGeoAABox, marker positions/directions, etc.).

Constraints / Conventions - Exactly 3 floats; no padding or w component. - Coordinate meaning depends on the parent structure (position vs. direction).

Matrix3x3¶

A 3×3 orientation (rotation) matrix stored as 9 floats in row-major order.
Total size: 36 bytes.

Row	Elements	Type	Bytes
0	`m00 m01 m02`	float	12
1	`m10 m11 m12`	float	12
2	`m20 m21 m22`	float	12

Usage
Represents orientation in CMatCoordinateSystem and other transforms. Stored/serialized as 9 consecutive floats.

Constraints / Conventions - Intended to be a rotation basis; normalization/orthogonality is expected by readers.
- Serialization is strictly 9 floats; no implicit translation.

Matrix4x4¶

A full 4×4 transform matrix stored as 16 floats in row-major order.
Total size: 64 bytes.

Row	Elements	Type	Bytes
0	`m00 m01 m02 m03`	float	16
1	`m10 m11 m12 m13`	float	16
2	`m20 m21 m22 m23`	float	16
3	`m30 m31 m32 m33`	float	16

Usage
Used where a complete affine transform is required (e.g., skeleton super-parent). Written row by row.

Constraints / Conventions - 16 floats, no extra padding.
- Meaning of the last column/row follows typical affine layout; specific interpretation depends on the consuming block.

CMatCoordinateSystem¶

Compact transform pairing orientation (Matrix3x3) with position (Vector3).
Total size: 48 bytes (36 + 12).

Field	Type	Bytes	Description
`matrix`	`Matrix3x3`	36	Rotation basis (row-major)
`position`	`Vector3`	12	Translation (x, y, z)

Usage - Core transform used by many blocks: SLocator, OBBNode, BoxShape, CylinderShape, SphereShape, etc.
- Always serialized as 9 floats (matrix) followed by 3 floats (position).

Constraints / Conventions - No scale component; scale is not supported.
- Consumers assume the matrix encodes a valid rotation basis.