Revision as of 13:00, 14 September 2017

m.pbrmetal is the most basic PBR-based material type used in Trainz, and should be the default material type of choice for any mesh unless some specific feature of some other material type is required. All PBR materials are defined using a multitude of texture channels (not just a simple RGB image) which define various aspects of the material on a per-texel basis. One major advantage of this approach is that a single in-game material can be used to display various different real-world materials, rather than requiring multiple separate in-game materials with different parameters. Trainz uses a Metallic/Roughness style PBR workflow.

This page describes content format v4.6 and assumes that the FBX file format is used as a data source for any meshes.

Texture Slots

The following texture slots are used for this material. All textures should typically have the same dimensions unless they represent a uniform color, however this is not strictly enforced.

Albedo

RGB: The albedo defines the base color of each texel. The sRGB color space is used.

Please note that there is no alpha channel support. For the most robust result, the alpha channel should be omitted or set to 1.0 (white). Note that unlike legacy Trainz materials, PBR materials do not autodetect opacity mode based on the texture in use. The content creator must select the appropriate material for their desired outcome. Runtime texture replacement should not expect to replace an opaque texture with a blended or masked texture and have the material update automatically.

Normal

RGB: Surface normal. This defines which way the surface is facing, relative to the interpolated vertex normals. Since this is an XYZ format rather than color data, it should never be modified in Photoshop. Using Photoshop to add a fourth channel or copy/paste smaller textures into an atlas is acceptable. Per-pixel manipulation or use of filters on the "RGB" channels is not acceptable.

Parameter

This texture is comprised of four separate channels which each form a separate data element. Linear color space (not sRGB) is used for these channels. R: Emissive. This causes the texture to have an internal glow, even when no external light is present. Used for phosphors, permanently-lit markings, etc. The glow color is based on the albedo. Note that this glow does not cast light upon surrounding surfaces except via the Bloom post-processing effect. G: Roughness. Defines whether the surface reflections are shiny (1.0) or matte (0.0). See the PBR metal workflow for details. B: Ambient Occlusion. Defines whether the surface is exposed to ambient lighting conditions (1.0) or affected only by direct lighting (0.0). A: Metallicity. Defines whether the surface is metallic (1.0) with the albedo used to colorize reflected light, or dielectric (0.0) with the albedo used to colorize the surface. While intermediate values are not physically accurate, they may be used to emulate subsurfaces which are partially metallic. See the PBR metal workflow for details.