Modelling Workflow
From primitives and profiles to a model dressed in physically-based materials.
Now you build for real. Form grows from primitives and from 2D profiles pushed into three dimensions — extrude, revolve, sweep, loft — and stays manageable through components and instances. Then you dress it: materials and textures, UV mapping, and the PBR model that makes a surface read as concrete, glass or timber under any light. Throughout, the central choice of solid versus mesh, and keeping the polygon count honest.
Learning objectives
By the end of this lesson, you will be able to — mapped to the course outcomes for Design of Structures I:
Create geometry from primitives and from 2D profiles using extrude, revolve, sweep and loft.
Compose and reuse a model with components and instances and organised layers.
Apply materials and textures, and explain UV mapping and the PBR material model.
Choose solid or mesh modelling and keep the polygon count appropriate.
Building and composing the model
Extrude, revolve, sweep and loft turn 2D profiles into 3D; components and instances keep the file light and consistent; and the solid-versus-mesh choice depends on whether the downstream task needs volume or just a surface.[1, 2, 3]
Extrude, revolve, sweep, loft
Four operations turn 2D into 3D: extrude pushes a profile straight along a direction; revolve spins a profile around an axis (a column, a dome); sweep runs a profile along a path (a moulding, a handrail); loft interpolates a surface between several cross-sections (a tapering tower). Most form starts as a profile.[1]
Materials and textures
A material starts with its base colour, UV-mapped onto the surface; the PBR model adds roughness, metallic and a normal map so it looks correct under any light. Bump and normal maps fake fine relief without adding geometry.[5]
Colour, mapped on
A material starts with its base colour (albedo). To place an image texture accurately on a 3D surface it must be UV-mapped — the surface 'unwrapped' into 2D so the texture aligns. Seamless/tileable textures repeat without visible seams; the tiling scale must match real size or the result looks wrong.[5]
At a glance
| Aspect | One | The other |
|---|---|---|
| Two profile ops | Extrude: push a profile straight | Revolve: spin a profile about an axis |
| Solid vs mesh | Solid: watertight, volume, fabrication | Mesh: facets, light, visualization |
| Geometry vs map | Model the detail (heavy) | Fake it with a normal/bump map (cheap) |
| Roughness 0 vs 1 | 0: smooth, sharp reflections | 1: rough, fully diffuse matte |
| Poly count | High-poly: detail, heavy, slow | Low-poly: light, fast, optimised by retopology |
Key terms
A basic built-in shape (box, cylinder, sphere) used as a modelling starting point.
The four ways to turn a 2D profile into 3D — push, spin, follow a path, interpolate.
A reusable definition placed many times; editing it updates all copies.
Unwrapping a 3D surface into 2D so textures align correctly.
A material defined by physical parameters — base colour, roughness, metallic, normal.
Roughness 0 = smooth/reflective, 1 = diffuse; metallic 0 = non-metal, 1 = metal.
A texture that fakes surface relief without adding geometry.
Rearranging/reducing polygons to optimise the count while keeping detail.
Studio task
Model a simple room and apply three PBR materials — a rough plaster wall, a polished stone floor and a glass window. Set the roughness for each and add a normal map to the plaster. Note how roughness and the texture scale change the read more than the base colour alone.
Self-assessment
1. Which operation spins a 2D profile around an axis to create 3D geometry?
2. In a PBR metallic/roughness material, a roughness of 0 gives —
3. Retopology is used to —
Recap
References & further reading
- [1]The four basic profile-to-3D operations — extrude, revolve, sweep, loft. https://www.learndesk.us/class/5153065298558976/lesson/5a1edc57e4c75ae291138c4ac7476661
- [2]SketchUp Help — components and instances for reuse. https://help.sketchup.com/en/sketchup/pushing-and-pulling-shapes-3d
- [3]Boundary Representation (solid) vs polygon mesh. https://www.sciencedirect.com/topics/engineering/boundary-representation
- [4]Polygon count, level of detail and retopology — CGAxis guide. https://cgaxis.com/polygon-count-guide-how-many-polys-do-you-really-need-in-2026/
- [5]What is PBR — physically-based rendering materials. Chaos. https://blog.chaos.com/what-is-pbr-physically-based-rendering-a-complete-guide
Further reading
- Daniel Tal, Rendering in SketchUp — modelling, components and materials.
- Wes McDermott, The PBR Guide (Adobe Substance) — physically-based materials.
- Blender Manual — modifiers, modelling and the material system.
Sources gathered and fact-checked June 2026. Published values vary by source, sample and method — treat as indicative and confirm against the cited standard before structural use.