Decals are a group of several areas defined manually on NDunes' ground, onto which you want to apply some local modifications. For each decal area, you can modify the soil, the plant densities, the elevation... which enables you to customize a local part of the generated NDunes' world.

Creating your first decal area

Create a new decal document, drag it in the current scene, and create your first decal area.

Select your decal area and start by defining the ground zone on which it will have effect using the curve tool. Try to pick your curve points on the ground as it will be more precise.

This area can either be a closed zone or a path with a specified width. Its contours can either be straight segments or bezier curves.

The falloff width defines a border inside the decal area where all the modifications (soil, plant densities..) will be blended smoothly with what was defined outside of the decal.

Setting your decal area properties

Now that your area is well defined, you can choose which modifications you want to apply in this area.

First set of parameters allows you to modify the terrain in the decal area. Add an height offset to elevate or dig the decal area.

Choose the flatten mode in the decal area : None (no flattening), "Fully flat" (to have a perfectly flat zone), or "Follow Primary" (to flatten the secondary soils but keep the primary soil elevation).

Second set of parameters allows you to add a custom soil to your decal area. If no custom soil is set, the soil that was previously defined in this area will be kept.

Choose a soil from the list of soil documents that are located in your working directory. Adjust height scaling and width to your liking. Adjust UV mapping of the soil texture using the provided sliders. If you want to use this custom soil's plant densities, tick the "override plant densities" checkbox (otherwise, plant densities of the terrain will be used even inside the decal area).

Third set of parameters allows you to customize the vegetation in your decal area. You can offset the plant densities per plant category inside the decal area.

You can also affect a spawn area to the decal area :

1) enter a name (of your chosing, without spaces) in the Biome Spawn Area field.

2) open the biome document that was loaded in your scene and for all the plants you want in your decal area, enter the same name in the "spawn decal areas" field.

Plants with a filled "Spawn decal areas" field will only spawn in the specified decal areas, unless you untick the "Only in spawn decal areas" checkbox in the biome view.

Decal areas with a filled "Biome spawn areas" field will only spawn matching plants. If you specify a "Biome spawn area" with no matching plant, no vegetation will appear in your decal area.

Creating several decal areas in the same decal document.

You can define as many decal areas you want in the same decal document. You will then be able to move them all at once by selectionning the decal document, and to order them to either override or blend with the others.

The area of effect and properties of each decal area are completely independant.

If you create several decal areas in the same decal document, you can define the order in which they will be applied. The highest decal area in the list corresponds to the "top" layer, which means it will be applied on top of all others. To reorder them, just drag and drop the decal areas in the list.

You can chose the behavior of each decal area in regards with the ones located under (in the list). 1) Override : means this decal area will override all lower decal areas, hence in the case they have overlapping zone of effect, only this decal area's properties will be displayed. 2) Blend : means this decal area will blend additively with all lower decal areas.

In the example above, Decal_Area_1 is the top layer and is set to "override", which is why the "Path" decal area properties are not visible in the area where they overlap.

Now with "Path" being the top layer, still in override mode, here is the result.

Finally with "Path" being the top layer, but in blending mode, here is the result.