Landscape Auto-Materials Explained: Terrain That Paints Itself by Height and Slope

Terrain that textures itself

Imagine you've imported a big landscape — rolling hills, a few cliffs, some snowy peaks. Hand-painting grass on every flat patch, rock on every steep face and snow on every summit would take hours, and you'd have to redo it the moment you sculpted a new valley. There's a much smarter way: an auto-material.

An auto-material is just a regular landscape material with one clever idea baked in. Instead of waiting for you to paint each texture by hand, it looks at every point on the terrain and asks two simple questions — 'how high am I?' and 'how steep am I?' — then picks the texture that fits. Flat ground at a low height becomes grass. Anything steep becomes rock. Anything high becomes snow. All automatically, and it updates itself the instant you reshape the land.

In this lesson we'll demystify how that works in plain English, meet the 'named layers' that make it possible, and clear up the single most confusing thing beginners hit: why a brand-new auto-material makes the whole landscape go solid black. Don't worry — by the end that black screen will make complete sense.

How the rules actually work

Inside the material, two pieces of information about each point on the terrain do all the heavy lifting.

Slope comes from the surface 'normal' — an arrow pointing straight out of the ground. On a flat meadow that arrow points almost straight up; on a sheer cliff it points sideways. The material measures how far the arrow has tilted from 'up' to get a steepness value, then uses it as a mask: where it's steep, show rock; where it's flat, show grass. There's a soft band in between so the rock fades into the grass instead of stopping at a hard line.

Height comes from the point's position along the world's up axis (its Z value). The material compares that height to a threshold you set — say, 'above this altitude, start blending in snow'. Below the threshold there's no snow; above it, more and more snow shows through, again with a soft band so the snowline isn't a razor edge.

Stack those two masks and you get the classic look for free: grass on low flats, rock wherever it's steep regardless of height, and snow capping the high ground. Crucially, none of these are pixels you painted — they're computed live from the terrain's own shape, so sculpting a new ridge instantly grows rock and snow on it with zero extra work.

What 'named layers' are — and why the material can't paint without them

Here's the part that explains everything else. A landscape material doesn't store its textures as one flat image. Instead it declares a set of named layers — think of them as labelled buckets: a 'Grass' layer, a 'Rock' layer, a 'Snow' layer. Each layer holds the textures for that surface, and each one has a weight at every point of the terrain, from 0 (invisible) to 1 (fully shown).

An auto-material's height and slope rules don't paint colours directly — they decide the weights of those layers. 'This point is steep, so set Rock's weight high here.' 'This point is high and flat, so push Snow's weight up.' The final look at any spot is just the layers blended together according to their weights.

But — and this is the whole trick — those weights live in data that belongs to the landscape, not the material. The material is the recipe; the per-point weights are the ingredients sitting in the landscape's own storage. When you first assign an auto-material, the landscape has no weight data for any of the material's layers yet. Every layer's weight is zero everywhere. Zero of everything blended together is nothing — and 'nothing' renders as solid black.

Assign an auto-material and bring the terrain to life

This assumes you already have a landscape in your level (from the heightmap lesson) and an auto-material in your Content Browser. Work top to bottom and tick each step — it stays ticked if you step away.

1. ✓
   1Select the landscape and assign the material

   With the mode dropdown on 'Selection', click your landscape in the viewport. In the Details panel on the right, find the 'Landscape Material' slot.

   Set it to your auto-material. If the material exists as a Material Instance, prefer that — instances let you tweak values later without recompiling. The terrain will very likely snap to solid black. Expected — keep going.

   TipAlways assign a Material Instance of the auto-material rather than the base material when you can. You'll thank yourself when you want to nudge the snowline later.

2. ✓
   2Switch to Landscape mode and open the Paint tab

   Open the mode dropdown (top-left, currently 'Selection') and choose 'Landscape'. The left panel becomes the Landscape tool.

   Click the 'Paint' tab. This is where the material's layers show up — and right now the Layers list is empty, because the landscape hasn't been told about them yet.

3. ✓
   3Create the layers from the assigned material

   In the Paint tab's Layers section, use the option to create layer info from the assigned material (often a 'Create Layers from Assigned Material' button, or a per-layer '+' / right-click that asks you to make a 'Layer Info'). This reads the material's named layers and adds a row for each — Grass, Rock, Snow, and so on.

   When prompted, choose a 'Weight-Blended Layer (normal)' info for each, and save the small Layer Info asset it creates. Now the landscape finally has somewhere to store each layer's weights.

   TipWeight-Blended is the right choice for an auto-material's blendable surfaces. The other option, Non-Weight-Blended, is for special single-pick layers and isn't what you want here.

4. ✓
   4Fill the base layer to give the rules something to work on

   Right-click the base ground layer (your Grass or 'Ground' layer) and choose 'Fill Layer'. This sets that layer's weight to full across the whole terrain in one go.

   The black instantly vanishes. Because the auto-material's slope and height rules are now operating on real weight data, cliffs show rock and peaks pick up snow on their own — you only had to fill the base.

   TipIf filling the base layer doesn't immediately wake the cliffs and peaks, that's normal for some auto-materials — the slope/height rules still need that first non-zero weight to blend against. Fill the base first, every time.

5. ✓
   5Eyeball the result and re-frame

   Switch the mode back to 'Selection', click the landscape, and press F to frame it. Fly around (hold the right mouse button and use WASD) and check the transitions: is the snowline where you want it? Are the cliffs reading as rock?

   Make a note of anything that looks off — too much snow, a hard grass-to-rock edge — because the next section is exactly how you tune those.

Tuning where the textures land

An auto-material isn't a black box you have to accept as-is. The two rules — slope and height — each have a few numbers you can turn, and if you assigned a Material Instance you can change them live without recompiling anything.

For the snowline, look for a height-threshold parameter (named something like 'Snow Height' or 'Snow Start Z'). Raise it to push snow further up the mountains; lower it to bring the snow down. There's usually a second value controlling how soft the transition band is — widen it for a gentle gradient, narrow it for a crisper snowline.

For the cliffs, look for a slope or 'rock angle' parameter. It sets how steep a surface has to be before rock takes over. Make rock appear on gentler slopes by lowering the angle, or keep rock to only the sheerest faces by raising it. Again there's typically a softness value for how gradually rock blends into grass.

Open your Material Instance (double-click it in the Content Browser), tick the parameters you want to control, and drag the sliders while watching the viewport. Because everything downstream of a Material Instance updates live, the whole terrain re-paints as you drag — no re-import, no re-fill.