Using Unity Polybrush to create a tiny planet with prefabs

In this Unity Polybrush tutorial, I'll be creating a tiny planet with prefabs. I'll show two tabs in Polybrush, the first to create terrain and the second to paint prefabs onto the planet. ► Download the prefabs that I've created for this tutorial: https://bit.ly/3eSCMsH (to Join my discord serve

This tutorial uses Unity's Polybrush to turn a plain sphere into a tiny planet — sculpting terrain bumps directly onto the mesh, then painting trees, rocks, and grass across it with a scatter brush. It's the fastest way to decorate organic surfaces without placing prefabs one by one.

Step 1 — Install Polybrush

In the Package Manager, search "polybrush" and install it. The window then lives under Tools → Polybrush Window — dock it wherever it's handy (next to the hierarchy works well). The canvas is a sphere with a green material; select it before doing anything, since Polybrush operates on the selected mesh.

Step 2 — Sculpt some terrain

Open the Sculpt Meshes tab. The brush has an outer radius and an inner radius — the two circles you see on the surface — plus a strength setting. Click and drag across the sphere and the mesh deforms upward into hills and ridges. A little goes a long way here; a few gentle bumps are enough to make the planet read as terrain rather than a beach ball.

Step 3 — Build a prefab palette

Switch to the Scatter Brush tab. The brush options are identical, but the bottom holds a palette. Use the dropdown's Add Palette to create one (it saves as a Polybrush data prefab palette asset — name it something like planet palette), then drag in your prefabs: a couple of plants, two rocks, and a few trees in this build.

Step 4 — Set per-prefab variation

This is where the scatter brush earns its keep. Select each palette entry and configure: the slider under each object is its frequency, so favorite trees can spawn more often than others just by dragging it. Scale can vary per axis or, better for props, uniformly — give the grass a range like 0.3 to 0.8 so no two clumps match. Set rotation on the Y axis from 0 to 360 so every placement lands at a random heading. Apply the same treatment to every entry; the randomness is what keeps the planet from looking copy-pasted.

Step 5 — Paint the planet

Check the box on a palette entry to load it into the brush, select the sphere, and click to paint. The Avoid Overlap option controls density: on, placements space themselves out evenly; off, you can pack trees into thick forest. Check all three trees at once and the brush picks randomly among them weighted by frequency — instant mixed woodland. Then uncheck the trees and do a grass pass, then a sparser rocks pass, concentrating them where a rocky outcrop makes sense. Layer by layer the sphere turns into a scruffy, lived-in little world — the same workflow scales to any terrain mesh in your game.