FIT1033 Chap.6 UV Mapping and Shell Layout
UV Mapping and Shell Layout
UV mapping makes a three-dimensional surface paintable in two dimensions. A useful layout accepts necessary cuts, places them along logical or less-visible boundaries, reduces local distortion and allocates texture resolution intentionally. The checker map is the central diagnostic because it reveals stretch, orientation and unequal texel density before painting begins.
Packing then balances shell scale, padding and efficient use of the 0-1 UV space.
What this chapter covers
- 01
Camera projection and initial shells
- 02
Logical seam placement
- 03
Character and prop shell separation
- 04
Checker maps and local distortion
- 05
Texel-density comparison
- 06
Padding and efficient UV packing
Worked example · free
Travel flask seams and checker
- 1Place a back seam, separate the base and preserve the front logo area.
- 1Flatten the shells and use a checker to diagnose the curved shoulder.
- 1Match texel density across comparable surfaces before packing.
- 1Arrange the shells with padding and no accidental overlap in the UV square.
Key terms
- UV Shell
- A connected section of flattened model surface within texture space.
- Seam
- A cut that allows a closed surface to unfold into separate UV boundaries.
- Texel Density
- Texture resolution assigned to each unit of model surface area.
- UV Distortion
- Stretch or compression produced when three-dimensional surfaces are flattened.
UV Mapping and Shell Layout FAQ
Where should I place UV seams?
Use less-visible areas, natural construction boundaries or material changes where possible. Keep important presentation surfaces continuous. A seam is a deliberate trade: it interrupts texture continuity but allows the shell to unfold with lower distortion, so several logical shells can be better than one forced shell.
What does a checker map reveal?
Checker squares show local stretch when they become rectangles, inconsistent texel density when their size changes between regions, and orientation problems when they turn unexpectedly. Apply the checker before detailed painting, because changing the UV layout later can invalidate masks, strokes and baked maps.
How tightly should UV shells be packed?
Use the texture square efficiently while preserving padding between shells. Large gaps waste resolution, but shells packed too closely can bleed into one another. Match shell scale according to surface area and viewing importance, then rotate and arrange them without accidental overlaps unless a deliberate shared layout is required.
Assessment move
Unwrap three objects with different topologies: a hard-surface container, a soft character and one environment prop. Before cutting, draw the planned seams on a screenshot. After flattening, compare that plan with the checker result and write down which cut reduced distortion or created a visible seam problem. Start every unwrap with a seam hypothesis.
On a screenshot, divide the model into surfaces that could lie flat and mark boundaries that are already hidden by construction, contact or a sharp material change. Predict which surfaces need cylindrical, planar or custom treatment, but treat the prediction as something to test. After the first unfold, place a checker on the asset and compare the result with the sketch.
A useful seam plan is supported by low distortion and manageable shells, not by how elegant the lines looked on paper. Learn to read the checker in several ways. Stretched rectangles indicate local distortion, changing square size indicates inconsistent texel density, and unexpected rotation can make directional materials difficult to paint.
Inspect curved transitions and narrow connectors closely, then decide whether moving vertices, relaxing a shell or adding one additional cut solves the problem with the least new visibility. Capture the model and UV editor together so every correction can be linked to a surface result. Practise scale before packing.
Choose two comparable surfaces on separate objects, measure how large the checker appears at the intended camera distance and normalise the shells until they read consistently. Then identify genuine exceptions such as a focal face or tiny background support. Write the reason beside each exception. This makes texel allocation a deliberate hierarchy instead of an accidental consequence of automatic layout.
When packing, preserve padding and orientation as well as occupancy; a nearly full square is not useful if shells bleed at lower resolutions. Compare a hard-surface object with an organic one. The container can often hide cuts along corners, bases and assembly lines, while the character needs seams that respect continuous visible forms and joints.
On both models, inspect mirrored or stacked regions carefully and use them only when the intended texture information can truly repeat. A unique stain, label or asymmetrical face requires unique space. Finish with a timed UV rehearsal following a simple completed model. Reserve fixed intervals for seam planning, unfold and checker repair, scale normalisation, packing and final inspection.
If time becomes short, protect readable shells and low distortion before chasing perfect square occupancy. Save the scene with the checker still available and export a UV snapshot if the painting stage needs one. The handoff is ready when you can point to every major cut, explain why it is placed there and show that the important surfaces receive controlled, consistent resolution.
