Populating an open world by hand is one of the most tedious parts of environment design. Placing thousands of trees, rocks, bushes, and ground cover across a 16 km² landscape would normally take a team days or even weeks. We did it in an afternoon.

This post walks through exactly how we approached it using the Procedural Placement Tool, what decisions we made along the way, and what the results looked like.

The Problem with Manual Placement

Hand-placing assets gives you maximum control, but it doesn't scale. On a small map, it works fine. On anything larger than a few square kilometers, you run into serious issues:

• Repetition fatigue — after the 500th tree, everything starts to look the same
• Inconsistent density — some areas end up sparse while others are overcrowded
• Time cost — a single biome can take an entire day to populate by hand
• Iteration friction — changing the art direction means starting over

We needed a system that could handle scale without sacrificing visual quality.

Setting Up the Biome Zones

The first step was defining our biomes. Our test landscape had four distinct regions:

• Dense forest — tall conifers with thick undergrowth
• Alpine meadow — open grassland with scattered wildflowers and boulders
• Rocky ridge — exposed stone with sparse vegetation
• Wetland — marshland with reeds, moss-covered rocks, and standing water

Each biome got its own placement layer with unique actor pools, density settings, and ground slope constraints. The biome zone system handles blending at boundaries automatically, so transitions between forest and meadow look natural without any manual tweaking.

Rule-Based Scatter in Practice

The key to believable procedural environments is rules. Real ecosystems follow patterns — trees don't grow on steep cliffs, wildflowers cluster in sunlit clearings, rocks accumulate at the base of slopes.

We defined rules for each actor type:

• Slope constraints — conifers only on slopes below 35°, boulders allowed up to 60°
• Altitude ranges — alpine flowers above 800m, marsh plants below 200m
• Proximity rules — minimum spacing between large trees, clustering for small ground cover
• Exclusion zones — no vegetation within 3m of roads or structures

These rules took about 30 minutes to set up. Once defined, the tool scattered over 100,000 instances across the full landscape in under 2 seconds.

Performance at Scale

Rendering 100,000+ instances could easily tank your frame rate. The Procedural Placement Tool uses Hierarchical Instanced Static Meshes (HISM) under the hood, which means the GPU handles instancing natively.

On our test hardware (RTX 3070, Ryzen 7), we held a steady 60 FPS with all four biomes fully populated. The multi-threaded placement calculation and spatial hashing for collision avoidance kept regeneration times under 2 seconds even at full density.

Iteration Speed

The real win wasn't just the initial placement — it was iteration speed. When our art lead decided the forest needed more undergrowth and fewer large trees, we adjusted two density sliders and hit regenerate. The entire 16 km² landscape updated in seconds.

Compare that to manually selecting and deleting hundreds of actors, then hand-placing replacements. What would have been a full day of rework became a 30-second adjustment.

Density Painting for Final Touches

After the rule-based pass, we used density painting for final polish. The viewport brush let us:

• Add extra foliage density around points of interest
• Thin out vegetation near gameplay paths for better visibility
• Create natural-looking clearings for combat encounters

This hybrid approach — broad rules for the base pass, targeted painting for details — gave us results that looked hand-crafted at a fraction of the time cost.

Results

The final landscape had over 140,000 placed instances across four biomes. Total time from empty landscape to fully populated world: roughly 4 hours, including iteration and polish passes.

A single artist did the entire thing. No scripting, no custom tools, no pipeline setup. Just the placement tool, a library of foliage assets, and a clear vision for each biome.

Try It Yourself

If you're building an open world in Unreal Engine, you don't need to hand-place every tree. The Procedural Placement Tool handles the heavy lifting so you can focus on the creative decisions that actually matter.

Check out the getting started guide to set up your first biome in under 10 minutes.