G—P / FMX 320 / Semester / Week 04

Week 04 · Phase 1 — Form by hand

UVs & unwrapping

A model with no UVs is a model that can't be textured. Today is one job, done properly: flatten your kit so that every piece can hold a texture at the same density, with seams you chose rather than seams that happened to you.

Sessions Mon Sep 21 & Wed Sep 23 · 2:00 – 3:50 pm · CCB-134 Bring your assembled kit from Week 3 — modeled, exported once, and walked in Unreal
This week, in practice

Monday is a catch-up on the walls. Bring your Week 3 kit and we get every piece standing in Unreal before anything else. The UV material on this page is real and it stays here, but we cover it over the next few weeks rather than in one afternoon — for anyone starting out in Blender and UE 5.8 it is bonus, not the bar.

Project 1 has a new goal: a game-ready kit and a playable level built from it, up and running. Imperfect UVs do not sink it; a level nobody can walk through does. The brief has been amended, and we pick UVs back up later in the term so that everyone knows how by the end. On Canvas the playable level is Assignment 1a Extended, the follow-up to the wall kit you already turned in, due at the Week 6 crit.

By the end of this week you can

Clean unwraps and consistent texel density come back later in the term, so that everyone knows how by the end. This week, the level.

Mon 2:00 · Brief Flattening for texture space

Unwrapping is the least glamorous hour in this course and the one that decides whether the next three weeks go well. Texturing a bad unwrap is like painting a wall that isn't flat — you can do it, and everyone will be able to tell.

Seams and unwrapping

A seam is a cut you authorise. The UV editor takes a closed 3D surface and lies it flat, and it can only do that by cutting somewhere — so the question is never whether to have seams but where you are willing to put them. Hide them where the eye doesn't travel: inside corners, under overhangs, along a natural break in the form. A seam on a flat visible face is a scar you will spend the texturing week trying to hide.

Blender in Edit Mode: a wall with a doorway, a column and a floor tile, every hard edge marked as a seam in red
A seam is a cut you authorise. A three-piece kit — wall with a doorway, column, floor tile — in Edit Mode, edge select, seams in red (Ctrl+E → Mark Seam). On hard-surface kit pieces every 90° corner is a natural break in the form, so every sharp edge is a seam: the doorway’s inside corners, the top, the ends. Nothing is cut across a flat visible face.

The test for a good unwrap is boring: no stretching, no overlapping where you didn't intend it, and islands laid out so a human could find their way around the texture.

Texel density

Texel density is pixels per unit of surface — how much texture resolution each piece actually receives. If one wall piece is at 512 px/m and the piece next to it is at 128, the second one looks blurry no matter how good the texture is, and no amount of painting will fix it. Consistency across a kit matters more than the number itself.

You measure it with a checker map, not by eye. Apply a checker, look at the model: even squares of even size mean even density. Squares that stretch mean the unwrap is distorted; squares that change size from piece to piece mean the density is inconsistent. This is the single most useful diagnostic in the whole course, and it takes ten seconds.

The kit unwrapped with no seams: the checker reads as rectangles and stripes, and the UV editor stretch overlay is yellow
Stretched. U → Unwrap with no seams at all. The checker on the wall reads as rectangles and on the column as stripes. The UV editor’s Stretching overlay (Overlays → Stretching, Area) paints anything distorted yellow; blue would mean faithful.
Each piece unwrapped to its own texture square: tiny squares on the column, huge on the wall, all islands stacked in the UV editor
Inconsistent. Every piece unwrapped on its own, each filling its own 0–1 square. Every square is square, but they are tiny on the column and huge on the wall — three densities in one kit. In the UV editor all three pieces’ islands are piled on the same square.

Trim sheets and layout

A trim sheet is one texture of reusable horizontal strips — edges, panels, pipes, trims — that many different pieces map onto. Instead of every object owning unique texture space, the whole kit shares one sheet. It is how modular environments are actually built in production: enormous coverage from a small memory budget, and a visual consistency you get for free.

Unique unwraps are for hero assets the camera will get close to. Trim sheets are for everything else. Knowing which you are making before you start unwrapping saves the entire afternoon.

The same kit mapped onto a trim sheet of five horizontal strips, each island a long band tiling along its strip
The same kit on one trim sheet. Five horizontal strips — rubber edge, metal trim, wood, stone, painted panel — each sized for one real-world height. Every face is a long island lying on its strip and tiling along it, and the whole kit shares one 1024 texture. Nothing in the UV editor is unique, and that is the point.
The rule for today

Overlapping UVs are a feature when you mean them — mirrored halves and tiling pieces share space on purpose and save real memory. They are a problem only for baking and lightmaps. Do not let the internet talk you into believing all overlap is a mistake.

Mon 2:45 · Guided lab Unwrap the kit

We unwrap one piece together, end to end, then you do the rest of your kit while I circulate.

  1. Mark seams

    Edge select, choose your cuts, mark them. Say out loud why each seam is where it is — inside a corner, along a form break, hidden from the main view. If you can't justify it, move it.

  2. Unwrap and inspect

    Unwrap, then open the UV editor beside the viewport. Look for islands that fold over themselves or stretch into ribbons. Fix by adding a seam, not by dragging vertices.

    UV Editing workspace: the wall unwrapped into flat rectangular islands over the checker, the checker even in the viewport
    The wall, unwrapped with its seams. UV Editing workspace, the UV editor beside the viewport with the checker image loaded (Image → New → UV Grid). Nine flat islands, every square square. A ribbon or a fold here means a missing seam — add one and unwrap again; do not drag vertices.
  3. Check texel density with a checker map

    Apply the checker to the whole kit at once. Walk the camera around it. Every square should be square, and roughly the same size on every piece. Note where it isn't — that's your fix list.

  4. Lay out the UVs efficiently

    Pack the islands. Straighten anything that wants to be straight — trims, panels, edges — because straight islands waste less space and are far easier to texture. Wasted UV space is wasted texture budget.

    All three pieces packed into one texture square at one density, squares matching on wall, column and floor
    Packed, at one density. UV → Average Islands Scale, then UV → Pack Islands. The three pieces now share one square at one density — the column’s squares match the wall’s — and the straight things are straight. Nothing overlaps unless you meant it.

Wed 2:00 · Workbench Practice, unhurried

No new material. You work on your own file while I circulate — this is the hour where the technique from the guided lab stops being something you watched and becomes something you can do.

  1. Unwrap the rest of your kit

    The lab covered one piece. The kit is three to five. This is the hour to finish them, with help two meters away.

  2. If you fell behind, catch up here

    Say so and I will come to you — do not spend the hour quietly stuck. Unwrapping is the week where quiet stuck-ness costs the most later.

  3. If you are ahead, go deeper

    Build a trim sheet layout for your kit and map two pieces onto it. Compare the texture space you save against unique unwraps.

  4. Ask Gary, the AI TA, anything

    The tutor on the course site is open all term for questions about how and why. It explains; you build. No agents in the work until Week 9.

Before you call it done

Wed 3:10 · Crit / share Checkers up

Screens up with the checker map applied — not the pretty view, the diagnostic view. We look at each other's kits for stretch and density mismatches, which are far easier to spot on someone else's work than your own. Bring the one seam you were least sure about.

Homework — due before Week 5

TaskDeliverable
Get every piece of your kit modeled, exported, and standing in one Unreal level you can walk through with a player start and collision.The level saved and backed up in your project folder; a screenshot of the walk.
Bonus, as far as you get: unwrap your pieces and put the checker on them.A checker screenshot in the class share, however imperfect.
Decide and note your texturing approach: unique unwraps, a trim sheet, or a mix.One short note in your process log saying which and why.

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