# trasformation matrix for model's bones

I was developing an fbx converter for legend of grimrock object model (www.grimrock.net), I just wanted to get the animations cause the rest has been converted by others' tools. I was reading all of their guidelines to convert from their little endian binary file to the format I want (in this case fbx) When I was about to construct the skeleton, I was stuck because of this

// A Mat4x3 is a transformation matrix split into 3x3 rotation and 3D rotation parts
struct Mat4x3
{
Vec3    baseX;
Vec3    baseY;
Vec3    baseZ;
Vec3    translation;
}


(btw Vec3 is a three dimensional vector (xyz) you can find complete specifications of their object model here)

what does "A Mat4x3 is a transformation matrix split into 3x3 rotation and 3D rotation parts" mean???? Regarding the creation of bones, I thoughtmatrix should be a transformation matrix not a rotation matrix. So I'm kinda confused. Anyway I should calculate this way? (o = origin)

x' = x*x1 + y*y1 + z*z1 + o1;
y' = x*x2 + y*y2 + z*z2 + o2;
z' = x*x3 + y*y3 + z*z3 + o3;

• Why not asking them what they mean by it? – Trilarion Oct 24 '14 at 12:53
• Well they simply didn't give any help and they didn't answer. Private messages on the forum to the developers is not permitted.. I'm getting crazy lol – kaomao Oct 24 '14 at 12:54

In this case, it seems likely that the 3D rotation in the comment is supposed to be a 3D translation.
In general, a 4x3 transformation matrix is like a regular 4x4 transformation matrix, but the fourth part with [0 0 0 1] is omitted for saving space and work.