Cas Files

.cas files are used for unit models and animations in RTW, unit animations in M2TW and strat map models and animations in both games. Cas is a proprietary format used by CA to export 3d models and animations from 3dsMax. Various modding tools exist to convert .cas files to either 3dsMax, Milkshape or Blender.

Format Types

The contents and structure of .cas files vary with use (with or without animation, with or without 'mesh') and according to when they were created. Uncompressed .cas files supplied with the games start with a version number, these numbers range from approx 2.1+ to 3.22, the version number can indicate changes to the format. 'Cas' files that are generated by 'unpacking' the animation packs do not return to the same format and do not have a version number.

Bone Weighting

Most .cas models with a skeleton only contain weighting to one bone per vertex, so each vertex will be 100% weighted to a particular bone, triangles that have vertexes weighted to different bones will stretch and contract as the bones are moved in an animation.

Mesh sections for primary and secondary weapons in RTW battle units will be weighted to one bone only, e.g. the right hand, in these type of mesh sections the bone number is given once at the top of the section and not repeated for each vertex.

Mesh sections for the body will typically have vertexes weighted to all of the available bones, but only one bone per vertex as described above.

Multi Bone Weighting

A few vanilla models actually have elements where vertexes have shared weighting across two bones. Typically these are the shoulder pad elements as used on the officer_roman_centurion model. The early .cas to 3dsMax converters do not handle these multi-weighted sections and simply fail to import them into Max.

The format of sections that have the multi-bone weighting is different.

The number of verts/tris that can be included in these sections seems limited, exceeding 100 verts/tris per groups or 200 verts/tris per case can crash the game or create visual effects similar to having unweighted bones.