.VTX File Format?

Question

I've recently taken the plunge into DirectX and have been messing around a little with Anim8or, and have discovered several file types that models can be exported to that are text based. I've particularly taken to VTX files. I've learned how to parse some basics out of it, but I'm obviously missing a few things.

It starts with a .Faceset with is immediately (on the same line) followed by the number of meshes in the file.

For each mesh, there is one .Vertex section and one .Index section in that order and the first pair of .Vertex/.Index sections are the first mesh, the second set are the second mesh and so on as you'd expect.

In a .Vertex section of the file, there's 8 numbers per line and an undefined number of lines (unless you want to trust the comments Anim8or has put just before the section, but that doesn't seem to be part of the specs of the file, just Anim8or being kind). The first 3 numbers correspond to X, Y, and Z coordinates for a particular point that'll later be used as a vertex, the other 5 I have no idea. A majority of the time, the last 2 numbers are both 0, but I've noticed that's not ALWAYS true, just usually true.

Next comes the matching .Index section. This section has 4 numbers. The first 3 are reference numbers to the Vertexes previously stated and the 3 points mark a triangle in the model. 0 meaning the first mentioned Vertex, 1 meaning the next one, and so on, like a zero-based array. The 4th number appears to always be -1, I can't figure out what importance it has and I can't promise it's ALWAYS -1. In case you can't tell, I'm not too certain about anything in this file type.

There's also other information in the file that I'm choosing to ignore right now because I'm new and don't want to overcomplicate things too much. Such as after every .Index section is:

.Brdf // Ambient color 0.431 0.431 0.431 // Diffuse color 0.431 0.431 0.431 // Specular color and exponent 1 1 1 2 // Kspecular = 0.5 // end of .Brdf

It appears to me this is about the surface of the mesh just described. But it's not needed for placement of meshes so I moved past it for now.

Moving on to the real problem... I can load a VTX file when there's only one mesh in the VTX file (meaning the .FaceSet is 1). I can almost successfully load a VTX file that has multiple meshes, each mesh is successfully structured, but not properly placed in relation to the other meshes. I downloaded an AT-AT model from an Anim8or thread in a forum and it's made up of 344 meshes, when I load the file just using the specs I've mentioned so far, it looks like the AT-AT is exploded out as if it were a diagram of how to make it (when loaded in Anim8or, all pieces are close and resemble a fully assembled AT-AT). All the pieces are oriented correctly and have the same up direction, but there's plenty of extra space between the pieces.

Does somebody know how to properly read a VTX file? Or know of a website that'll explain what those other numbers mean?

Edit:

The file extension .VTX is used for a lot of different things and has a lot of different structures depending on what the expected use is. Valve, Visio, Anim8or, and several others use VTX, I'm only interested in the VTX file that Anim8or exports and the structure that it uses.

Answer 1

Based on some googling, it seems you're at the wrong end of the pipeline. As I understand it: A VTX file is a Valve Proprietary File Format that is the result of a set of steps.

The final output of Studiomdl for each Half-Life model is a group of files in the gamedirectory/models folder ready to be used by the Game Engine:

• an .MDL file which defines the structure of the model along with animation, bounding box, hit box, material, mesh and LOD information,
• a .VVD file which stores position independent flat data for the bone weights, normals, vertices, tangents and texture coordinates used by the MDL, currently

• three separate types of VTX file:

  • .sw.vtx (Software),
  • .dx80.vtx (DirectX 8.0) and
  • .dx90.vtx (DirectX 9.0) which store hardware optimized material, skinning and triangle strip/fan information for each LOD of each mesh in the MDL,
• often a .PHY file containing a rigid or jointed (ragdoll) collision model, and sometimes
• a .ANI file for To do: something to do with model animations

Valve

Now the Valve Source SDK may have some utilities in it to read VTX's (it seems to have the ability to make them anyway). Some people may have made 3rd party tools or have code to read them, but it's likely to not work on all files just cause it's a 3rd party format. I also found this post which might help if you haven't seen it before.

Answer 2

Hi, I have been working on a 3D Modeling program myself and wanted a simple format to be able to bring objects in to the editor to be able to test the speed of my drawing routines with large sets of vertices and faces. I was looking for an easy one where I could get models quickly and found the .vtx format. I googled it and found your question. When I was unable to find the format on the internet, I played around and compared .OBJ exports with .vtx ones. (Maybe it was created just for Anim8or?) Here is what I found:

1) Yes, the vertices have eight numbers on each line. The first three are, as you guessed, the x, y, and z coordinates. The next three are the vertex normals, nx, ny, and nz. You may notice that each vertex appears multiple times with different normals for each face that contains it. The last two numbers are texture coordinates.

2) As for the faces, I reached the same conclusions as you did. The first three numbers are indices into the vertex list above. The last number does appear to always be -1. I am going to assume that it has something to do with the facing of the face. (e.g. facing in or out.) Since most models are created with the faces all facing appropriately, it stands to reason that this would be the same number for all of them.

3) One additional note: When comparing the .obj with the .vtx, I did notice that the positions of the vertices changed. This was also true when comparing with the .an8 file. This should not be a "HUGE" problem as long as they are all offset by the same amount in each vertex and every file. At least then it could be compensated for.

Have you considered using the .obj file format? It is text-based and is not extremely difficult to parse or understand. There is quite a bit of information about it online.

I am going to add that, after a few hours inspection, the vtx export in Anim8or seems to be broken. I experienced the same problem as you did that the pieces were not located properly. My assumption would be that anim8or exports these objects using the local coordinates for each mesh and not accounting for transformations that have been applied. I do also note that it will not IMPORT the vtx file...