HowTo/Build a cab interior

Trainz uses an interior object to represent a locomotive cab, or view from another vehicle, e.g. a passenger coach, brake van or caboose. Interiors can also be attached to some non-train assets. For this howto, I am going to assume that we are creating a traincar interior, and focus primarily on a cab interior for a diesel or electric locomotive.

Basic structure

The basic structure of a cab is quite similar to a number of different assets. You will have a main mesh with a number of attached sub-meshes, which are arranged using a mesh-table.

The main cab mesh typically consists of the interior walls, roof and floor of the cab, the control desk or stand, all furniture or other static objects visible inside the cab, and also all parts of the locomotive exterior that are visible from inside the cab - e.g. the top of any projecting nose below the cab windows. Remember to consider the sightlines out of rear windows too for visible bodywork panels - the user can move around the cab and rotate the camera to any angle. Users are not restricted to looking forward out of the front windows only.

Artwork considerations

There are some differences in style between the construction of an interior object and a typical trainz object.

Except in very specific circumstances, there will not be more than one interior object in existence at any time, and that interior is always viewed from very close range - the user is inside it. Because of this, interiors are typically modelled with a high polygon count and with high resolution textures, to give an impressive visual feel. LOD is not used, as the user never gets far enough away from the interior for LOD techniques to have worthwhile benefit.

Trainz lights interior objects differently to map objects like buildings and other scenery - the main illumination is ambient, not directional. (A steam loco does have a directional light coming from the firebox, but a diesel or electric cab typically has no directional light inside, and relies entirely on ambient illumination).

With ambient illumination, effects such as normal and specular mapping do not have much (if any) effect. Because of this, more effort needs to be put into the diffuse texture for a cab interior than would normally be applied to Trainz objects. Drawing or baking shadows and other effects into the diffuse textures is required to produce a nice looking cab interior.

A basic config file

The minimal required config for an interior to show in-game is:

kind                                    interior
kuid                                    <kuid2:YOUR:KUID:HERE>
trainz-build                            2.9
username                                "Your interior name here"
category-class                          ZI

mesh-table
{
  default
  {
    mesh                                "your_interior_mesh_name.im"
    auto-create                         1
  }
}

Note: There are also other base tags that should be added that are common to all asset types - e.g. the download station will require a valid thumbnails container before the asset can be uploaded. See the documentation for KIND_TrainzBaseSpec for details of tags which apply to all trainz assets. Depending on which Trainz version you have and which trainz-build number you have specified, some of these may be required - content manager will tell you what is required, listing missing tags as errors.

camera positions

If we load a cab up with that config file, we will note that the view is not particularly appealing. Chances are we're right down near the floor. To fix this, we need to define some default positions for camera views. This is done with the cameralist container and the cameradefault tag. Add the following to your config.txt file:

cameralist
{
  camera0                               0,0,2,0,0
}

cameradefault                           0

The cameralist container can contain any number of cameras, but they must be numbered sequentially and start at zero.

The five numbers are the X, Y and Z coordinates of the camera in metres relative to the 0,0,0 point of the interior mesh, and the Yaw and Pitch in radians. Luckily you don't have to work these values out from scratch - add the line "-freeintcam" to your trainzoptions.txt file, and you can move the camera about in the cab with the mouse and keyboard, and the precise position will be displayed in the bottom right corner.

When you have found a position you like, write the numbers down. When you've got a good selection of positions recorded, add them to the cameralist container.

You may wish to return to this and tweak the values later once all the controls are in place - but it's handy to have a good starting position for the camera while testing.

-~= To Be Continued... =~-