Trim Sheets for Games: What They Are and How to Make One

A trim sheet is one texture that holds a set of thin horizontal strips: bevelled edges, panel seams, rubber seals, bolts, metal trims and flat surfaces. Each strip tiles from left to right. Instead of giving every wall, door frame and pipe its own unique texture, you lay the UVs of many different models over those shared strips. One texture set ends up covering a whole room of assets.

That is why trim sheets are everywhere in game environment art. They save texture memory, keep detail sharp on large surfaces and let a small team texture a big level fast. This guide explains what a trim sheet is, how it differs from a texture atlas, how to plan and make one, and how to UV your models to use it in Blender and Unreal Engine.

What is a trim sheet?

Picture a square texture, often 2048 or 4096 pixels, sliced into horizontal bands of different heights. A thick band might be a riveted metal panel. A thin band might be a chamfered edge that catches the light. Another might be a strip of cable, a vent grille or a painted warning stripe. Each band tiles horizontally, so you can stretch a model's UVs along it as far as you like without a visible seam.

A full trim sheet is a complete PBR texture set (PBR means physically based rendering, the standard way games describe materials). That usually means base colour, normal, roughness and metallic maps, often with ambient occlusion and height packed in as well. The normal map does most of the work. It is what makes a flat strip of polygons read as a bevelled edge or a raised seam. If normal maps are new to you, read our guide on what a normal map is and how normal mapping works first.

You see trim sheets most on hard surface environments: sci-fi corridors, industrial buildings, castles, modern interiors. Anywhere with repeating edges, panels and architectural detail is a good fit. Trim sheets help a team finish a full environment on time. In CADA's Certificate in 3D for Games, each term has a team project, and one of them is a walkable story environment.

Trim sheets vs texture atlases vs tiling textures

These three terms get mixed up. They solve different problems.

• Tiling texture: repeats in both directions, like a brick wall or a concrete floor. Good for large flat surfaces. Bad at edges, because there is nothing to suggest a bevel or a border.
• Texture atlas: packs several unique, non-repeating images into one texture, like a sprite sheet or a set of baked prop textures. Its main job is to let several objects share one material, which can cut draw calls (the number of separate requests the engine sends to the graphics card). An atlas does not tile.
• Trim sheet: a kind of atlas built from strips that tile in one direction. You get the sharing benefit of an atlas and the endless length of a tiling texture, plus edge detail a tiling texture cannot give you.

Most production environments use all three together. Tiling textures cover floors and big walls, trim sheets handle the edges, frames and repeating details, and a few hero assets get their own unique bakes.

Why game studios use trim sheets

Memory and performance

Every unique texture set costs memory. A level with fifty props that each have their own 2K maps fills the budget quickly. If thirty of those props share one trim sheet, you load one texture set instead of thirty. Fewer material slots per mesh means fewer draw calls, and shared materials make merging and instancing easier.

Sharp detail at any size

A unique bake spreads a fixed number of pixels across the whole model. On a ten-metre wall, that gets blurry. A trim strip tiles, so a ten-metre edge gets the same crisp detail as a one-metre edge. Texel density, the number of texture pixels per metre of surface, stays even across the scene. Our UV mapping guide explains texel density in more detail.

Speed and consistency

Once the sheet exists, texturing a new asset is mostly a UV job. You can build a door, a pillar or a console in an afternoon and it will match everything else in the level, because it uses the same materials. Changing the sheet updates every asset that uses it.

The trade-offs

Trim sheets are not free. They take planning before you build anything. Repetition can show if you lean on the same strip too often. They also suit modular, hard surface work better than organic shapes: a rock, a tree trunk or a character still needs its own texture. Use trims where they fit and do not force them everywhere.

How to plan a trim sheet

Most beginner trim sheets fail at the planning stage, not the texturing stage. The sheet gets built first and the assets later, and half the strips never get used. Work the other way round.

1. Collect reference for the space. Look at the room or building you are making and list the details that repeat: edge bevels, panel seams, door frames, skirting, pipes, vents, bolts, rubber seals.
2. Block out the assets first. Rough out the walls, frames and props in simple geometry. You will see which edges need detail and how wide those edges are in real units.
3. Decide the strip heights. Keep heights to clean fractions of the sheet, such as 1/8, 1/16 or 1/32 of the texture. That makes UV snapping simple and keeps texel density consistent. Give the details you use most the most space.
4. Leave gaps between strips. Add a few pixels of padding between bands. When the engine shrinks the texture at a distance (mipmapping), neighbouring strips can bleed into each other. Padding stops a thin chrome edge picking up colour from the rust strip next to it.
5. Keep one or two flat strips. A plain strip of each main material, with no edge detail, is useful for filling flat faces on the same object without switching materials.

A first trim sheet with six to ten strips is plenty. Studios often keep a small number of sheets per environment, for example one for metal and structure and one for interior details, rather than one giant sheet that tries to do everything.

How to make a trim sheet

Build the high-poly strips

The common method is to model the detail as real geometry, then bake it to a flat plane. In Blender, start with a plane the same proportions as your sheet. Model each strip as a long piece of high-poly geometry lying on that plane: bevelled edges, grooves, rivets, raised panels. Sculpt damage in ZBrush or Blender's sculpt mode if the style needs it. Keep the ends of each strip clean and identical so the detail tiles without a break.

Bake the maps

Bake the high-poly strips down to a single flat, low-poly plane. Bake in Substance 3D Painter, which gives you normal, ambient occlusion, height and curvature maps and exports the normal map in DirectX format. As with any prop bake, the plane is the target and the strips are the source. Check the result for seams at the left and right edges. If the strip does not tile cleanly here, it will not tile on the model either.

Texture it

Bring the baked maps into Substance 3D Painter or Substance 3D Designer and texture the strips as one material. Curvature and ambient occlusion drive edge wear and dirt, so a painted metal trim picks up chips on its bevels without hand painting. Keep wear subtle. Strong, unique marks like a large scratch or a stain will repeat every time the strip tiles and the eye spots it at once.

Export

Export your maps in the format your engine expects. For Unreal Engine, a common set is base colour, a normal map in DirectX format, and a packed texture with ambient occlusion, roughness and metallic in the red, green and blue channels.

How to UV a model for a trim sheet

This is the part that takes practice. The goal is to place each face of your model over the strip that matches it, with the UVs straight and the texel density correct.

1. Model with trims in mind. Add edge loops where you want a trim to start and stop. A bevelled edge on a wall needs a strip of faces running along it, roughly as wide as the bevel strip on your sheet.
2. Unwrap face strips, not whole objects. In Blender, select a run of faces along an edge, unwrap them, then straighten them into a clean rectangle. Follow Active Quads, in the Unwrap menu, is useful here: straighten one quad by hand, make it active, and Blender lines up the rest of the strip to match it.
3. Snap to the strip. Scale the UV island vertically so it fits exactly between the top and bottom of the target strip. Turn on snapping and set the grid to match your strip heights so islands lock into place.
4. Let it run off the sheet. Because the strip tiles horizontally, the island can extend past the left or right edge of the UV square. Scale it horizontally only to set the texel density, not to fit inside the square.
5. Check in the viewport. Apply the trim material in Blender and look at the model as you go. Stretched rivets, squashed panels or a bevel that sits on the wrong edge are easy to spot and quick to fix.

A common beginner mistake is placing a bevel strip on faces that are not actually at an edge. The normal map then draws a bevel in the middle of a flat surface and the asset looks wrong. Another is ignoring the direction of the strip: if the panel lines run the wrong way, rotate the island by 90 degrees.

Using trim sheets in Unreal Engine

In Unreal, set up one master material for the trim sheet, then make material instances from it for colour or roughness variations. Every asset that uses the sheet shares that material. Make sure the texture uses wrap tiling, the default, so UVs that run past the edge of the sheet repeat as intended.

Trims work well alongside decals and vertex painting. Decals add one-off details such as signs, stains and damage that would look repetitive on the sheet itself. Vertex painting lets you blend in dirt or a second material across a large surface.

What studios look for

Environment art leads reviewing a portfolio want to see that you understand budgets, not just that you can make something look good. A strong trim sheet piece shows:

• the sheet itself, with a clear breakdown of which strip does what;
• several different assets textured with that one sheet;
• a wireframe and UV view, so they can see the UVs are straight and the density is even;
• a finished scene in Unreal where the trims sit alongside tiling textures and a few unique assets.

One small, well-planned room built from a single trim sheet says more about your skills than a dozen unrelated props with their own unique bakes.

Where to go from here

Trim sheets build on skills you need anyway: hard surface modelling, clean UVs, baking and PBR texturing. If you are new to 3D and those words are still unfamiliar, start with the free Blender 3D Bootcamp. It is six live online sessions over three weeks, recorded, with no experience needed, and it ends with a first look at Unreal Engine.

If you are ready to commit to game art, the Certificate in 3D for Games is 60 weeks online, with recorded lectures, a weekly live feedback session and team projects each term: a walkable story environment, a playable level and a vertical slice. You need no 3D experience or portfolio to apply.