Terrain Materials

Terrain materials are used for the coloration of the terrain. Beside the ground itself, it is possible to use both 2D textured grass and small 3D models as grass and plants.

The terrain materials themselves are defined in .tmat.lua files and have some specific parameters:

function data()
return {
  menuCategory = {
    categories = {
      {
        category = "landscaping_ground",
        filterCategories = {"grass"},
        order = 635,
      },
    },
  },  
 
  description = {
    name = _("Grass Cutted Light"),
    desc = _("Paint the ground with the materials brush."),
    icon = "grass_cutted_01.tga",
    previewIcon = "grass_cutted_01_preview.tga",
  }
 
  categoryList = {
    categories = { "all.clima", }
  },
 
  detailColorTexture = "tex/grass_cutted_01_albedo.dds",
  detailMetalGlossAoHTexture = "tex/grass_cutted_01_metal_gloss_ao_h.dds",
  detailNormalTexture = "tex/grass_cutted_01_nrml.dds",
  overlayTexture = "/terrain/materials/shared/tex/overlay_0.dds",
 
  grass = "grass_cutted_01.grass",
 
  detailSize = 1 / 32,
  overlaySize = 0.03,
  overlayStrength = 0.25,
  hOffset = 0.3,
 
  priority = 1,
}
end

The menuCategory struct is used to provide the material in the right menu. See the construction menu for more details about the menu tags.

The description properties contain data used for the menu entry in the construction menu. This covers:

• name for the display name. It should not be longer than 32 characters.
• description for a short descriptive text highlighting the individuality of the terrain material. It should not be longer than 320 characters.
• icon is a reference to a small @2x.tga icon which has a resolution of 240×150 pixels shown in the menu.
• previewIcon is reference to a .tga image that is used as background image for the info box. It has a resolution of 720×405 pixels.

The categoryList.categories is a list of tags that are used in the terrain generation process and climate filtering. Entries that equal the filename of a climate are used to assign the model to a certain climate. It will not be available in other climates.

The texture applied to the terrain is defined by the following properties:

• detailColorTexture is a reference to a texture file that is used for the ground color.
• detailMetalGlossAoHTexture is a reference to another texture that is used for the physical effects. The alpha channel is used as a heightmap for the ground texture.
• detailNormalTexture is a reference to a texture that is used for the normal map of the ground.
• overlayTexture is a reference to a texture that is used as a irregularity overlay to break the tile tessellation effect of the main detail texture.

With grass it is possible to reference a resource describing the grass and plants that shall be used for the terrain material. See below for further details.

The next set of properties is used to scale the textures from above:

• detailSize is the scaling factor of the detail texture.
• overlaySize is the scaling factor of the overlay texture.

There are several other properties:

• overlayStrength is the intensity factor for the overlay texture.
• hOffset is an offset that is added to the texture heightmap of detailMetalGlossAoHTexture. At the edge of a materials area, the terrain material that has the greater height value is visible.
• priority is a number that sets the priority of the terrain material. The material with the highest priority is painted on top. This is used to ensure that e.g. asphalt is displayed above the dirt ground. When terrain materials are painted manually, this property is ignored.

It is possible to define additional plant sprites that are shown above the ground (as long as they are not deactivated in the graphics settings) as well as select some small plant asset models to be used. They are defined in .grass.lua files:

function data()
return {
  colorTexture = "/terrain/materials/grass_alpine/tex/grass_alpine_albedo_opacity.dds",
  metalGlossAoTexture = "/terrain/materials/grass_brown/tex/grass_brown_metal_gloss_ao.dds",
  normalTexture = "/terrain/materials/grass_brown/tex/grass_brown_normal.dds",
  translucencyTexture = "/terrain/materials/grass_brown/tex/grass_brown_translucency.dds",
 
  width = 1.0,
  height = 1.0,
  density = 0.0, -- stems per square meter (range allowed 0 to 16) 
  lodDistance = 300.0,
 
  assets = {
    {
      filePath = "/assets/vegetation/plants/fern_01/fern_01.mdl",
      density = 0.01,
      scaleMin = 0.8,
      scaleMax = 1.1,
    },
    ...
  }
}
end

For the 2D grass, there are properties for texture references as well as the geometric parameters. The graphics are defined by some properties:

• colorTexture is a texture reference for the color and transparency.
• metalGlossAoTexture is a texture reference for the physical effects.
• normalTexture is a texture reference for the normal map effect.
• translucencyTexture is a texture reference for the thickness of the plant. Thin areas let the sun shine through the backside to entlight the front side. Thick areas are fully shaded.

The size and distribution of the faces on which the texture is projected are defined with another set of properties:

• width is the width of the face in meters.
• height is the height of the face in meters.
• density is the number of plants per square meter. The allowed range is from 0 to 16.
• lodDistance is the maximum distance from where the plants are visible.

To use simple plant models, the assets list can have one or more entries with the following properties:

• filePath referencing a .mdl file.
• density is the number of plants per square meter.
• scaleMin and scaleMax are used to scale the