Shader Family: land_mesh_combined_decal

Overview

We use several shaders for object geometry to apply decals to the terrain. This is not to be confused with simple ground decals, which apply directly to the terrain geometry – that’s a different topic. Here, we are dealing with geometric decals.

When do we need to apply a decal to the terrain using geometry? When we want to modify the landscape’s geometry and add some new color (and possibly details). A good example would be airfields. Given their large size, it’s impractical to render them as full-scale models with unique textures (or tiled textures), as this would result in a poor texel density. Moreover, they wouldn’t blend seamlessly with the surrounding terrain – there would be harsh transitions between textures.

The solution is decals. For example, if you want a snowy airfield in a desert, you can achieve this with decals. All decals are prefabs – they are baked into the level’s geometry.

There are several shaders we can use for this:

1. land_mesh_combined and its dynamic version dynamic_combined_decal

2. land_mesh_combined_detailed_decal and its dynamic version dynamic_combined_detailed_decal

3. land_mesh_combined_mixed_decal and its dynamic version dynamic_combined_mixed_decal

Important

The difference between dynamic and static shaders boils down to two key points:

• Static shaders are applied to prefabs, while dynamic shaders are applied to dynamic models (for simplicity, think of them as models with dynamic shaders).

• Objects with dynamic shaders can only be placed through the MissionEditor as units (whether they’re part of an object group or a dynamic object). In contrast, static objects are placed directly as entities in the Landscape tab.

land_mesh_combined / dynamic_combined_decal – Basic Shader

This is the simplest shader in the family. It has no parameters and applies only a decal texture to the geometry. The typical material configuration looks like this:

material{
  name:t="airfield_side"
  class:t="land_mesh_combined"
  tex0:t="./norway_herdla_airfield_empty_alpha.tif"
}

The decal texture represents the diffuse component of what we are applying. The alpha channel controls the transparency of the decal.

For example:

Airfield on the Map	Decal Diffuse	Decal Alpha

Currently, this basic shader is rarely used because the need for greater detail, even for aircraft-related assets, has increased. However, it’s sometimes applied to the “manchette” of airfields (the curved edges used to blend the airfield surface with the surrounding terrain). In such cases, the shader with a transparent alpha texture is assigned to this geometry:

land_mesh_combined_detailed_decal / dynamic_combined_detailed_decal – Shader with One Detail Layer

This shader works with three textures:

• Slot 1: decal texture with transparency in the alpha channel.

• Slot 2: diffuse detail texture.

• Slot 3: _r detail texture.

The first two slots are self-explanatory. The _r texture requires further reading, but in short, it contains a height map, microdetail index, smoothness, and reflectance. Based on these parameters, the detail on the terrain is embossed and exhibits the physical properties of the desired material.

Important

This _r texture is not the same as the one used for landscapes! On landscapes, the _r texture includes reflectance, ambient occlusion, microdetail index, and smoothness.

This shader has the following parameters:

• script:t="detail1_size_ofs=0.25,0.25,0,0" – this offsets the detail texture (effectively controlling the tiling).

A typical material configuration looks like this:

material{
  name:t="smolensk_aero_south"
  class:t="land_mesh_combined_detailed_decal"
  script:t="detail1_size_ofs=64,32,0,0"
  tex0:t="smolensk_aero_south_tex.tif"
  tex1:t="detail_soil_cracked_tex_d.tif"
  tex2:t="detail_soil_cracked_tex_r.tif"
}

The logic is the same as in land_mesh_combined, except that this shader adds a detail layer to the decal texture. Essentially, in this case, the decal acts more as an overlay because of its large texel size, which results in a blurred appearance.

The fine details come from the detail and microdetail textures. For instance, fine textures such as small cracks or wear patterns are handled by the detail layers, while larger surface elements, like ruts or pathways, are represented by the decal.

land_mesh_combined_mixed_decal / dynamic_combined_mixed_decal – Shader with Four Detail Layers

This is the most advanced shader in the family. It operates similarly to land_mesh_combined_detailed_decal but supports up to four detail layers instead of one.

Important

There’s a known issue: if an object has mapping in the third channel, its texture on the ground may appear semi-transparent. Avoid using unnecessary mapping channels.

Important

The dynamic version is not suitable for large surfaces (hundreds of meters) made of dense materials (concrete, asphalt, etc.), as it becomes semi-transparent when viewed from a distance. For example, you might notice that the markings and runway seem to fade when seen from far away.

Shader Textures

The shader works with 10 textures:

• Slot 1: decal

• Slot 2: detail blending mask

• Slot 4: diffuse texture for detail layer 1

• Slot 5: _r texture for detail layer 1

• Slot 6: diffuse texture for detail layer 2

• Slot 7: _r texture for detail layer 2

• Slot 8: diffuse texture for detail layer 3

• Slot 9: _r texture for detail layer 3

• Slot 10: diffuse texture for detail layer 4

• Slot 11: _r texture for detail layer 4

The blending mask is an RGB mask where:

• R-channel represents detail layer 1

• G-channel represents detail layer 2

• B-channel represents detail layer 3

• Areas with less than 100% brightness in all channels will display detail layer 4.

Note

Don’t worry if the fourth detail layer appears in areas without detail layers 1, 2, or 3. The final decal’s visibility is controlled by the decal’s alpha transparency, meaning you can control the appearance of all details, including the fourth layer, using the transparency mask.

For example:

Airfield on the Map	Decal Diffuse

Decal Alpha	Blending Mask

In this case:

• The blue channel defines the pathways.

• The alpha mask smooths the edges of other detail layers, making them transparent and revealing the fourth layer.

• All channels together create a multicolored effect on the runway, blending different types of sand, dirt, and rocks.

Some examples use more defined masks:

Airfield on the Map	Decal Diffuse

Decal Alpha	Blending Mask

In this case:

• R-channel represents concrete.

• G-channel represents concrete slabs.

• B-channel represents dirt.

• A-channel (black in the mask) represents dirt paths and dust along the edges of the concrete and slabs.

All these elements appear based on the decal’s alpha transparency.

Parameters

• script:t="detail1_size_ofs=0.25,0.25,0,0" – detail layer 1 texture offset (tiling)

• script:t="detail2_size_ofs=0.25,0.25,0,0" – detail layer 2 texture offset

• script:t="detail3_size_ofs=0.25,0.25,0,0" – detail layer 3 texture offset

• script:t="detail4_size_ofs=0.25,0.25,0,0" – detail layer 4 texture offset

A typical material configuration looks like this:

material{
  name:t="markup_1"
  class:t="land_mesh_combined_mixed_decal"
  script:t="detail1_size_ofs=128,64,0,0"
  script:t="detail2_size_ofs=128,64,0,0"
  script:t="detail3_size_ofs=128,64,0,0"
  script:t="detail4_size_ofs=256,128,0,0"
  tex0:t="afghan_airfield_bagram_tex.tif"
  tex1:t="afghan_airfield_bagram_tex_mask.tif"
  tex3:t="detail_asphalt_a_tex_d.tif"
  tex4:t="detail_asphalt_a_tex_r.tif"
  tex5:t="detail_concrete_tex_d.tif"
  tex6:t="detail_concrete_tex_r.tif"
  tex7:t="detail_concrete_tex_d.tif"
  tex8:t="detail_asphalt_cracks_tex_r.tif"
  tex9:t="detail_sand_ground_tex_d.tif"
  tex10:t="detail_sand_ground_tex_r.tif"
}