Modelling Workflow & Interoperability

By the end of this lesson, you will be able to — mapped to the course outcomes for Interior Computer Studio II:

The danger is not that a format loses data — it is that it loses it with no warning. Know what each carries, pick the right one for the destination, and check the receiving end. And set your units first.^{[1, 2, 3]}

Pick where the model is coming from and where it is going, and watch exactly which properties are dropped silently — coloured the alarm colour, because no export dialog will ever warn you.

A normal map fakes surface relief for light but moves no vertices, so it is invisible at the edge. Break the outline — a jaali, a cornice, carved teak — and it must be real geometry; leave the surface flat — plaster, weave, grain — and a map suffices. And “more polygons is better” inverts once triangles shrink below a pixel.^{[4, 5]}

Take one room you have modelled and make two lists. First, the hand-off: name every tool the model will pass through from your desk to a finished client image, and for each transfer say which format you would use and one thing it will drop. Second, the geometry budget: list ten surfaces in the room — a cornice, a jaali, a rug, a plaster wall, a turned table leg — and mark each “real geometry” or “normal map” using the silhouette test alone. Then check yourself: is anything you marked “real” actually flat at the edge, and anything “map” actually breaking the outline? Fixing those two mistakes is most of what makes a model both convincing and light.

1. [1]Blender Foundation. Blender Manual — Import & Export (OBJ, FBX, glTF 2.0, etc.), on what each format carries and drops. docs.blender.org. https://docs.blender.org/manual/en/latest/files/import_export.html
2. [2]Khronos Group. glTF 2.0 Specification: 'The units for all linear distances are meters'; 'glTF uses a right-handed coordinate system … +Y is up.' Metallic-roughness PBR material model. https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html
3. [3]Autodesk & Trimble product documentation on internal/system units (3ds Max default system unit = inch; SketchUp works internally in inches). On the 1/25.4 import-scale error.
4. [4]Cignoni, P. et al. (1998). A general method for preserving attribute values on simplified meshes (IEEE Visualization 1998) — the ancestor of the bake-high-to-low normal-mapping workflow. https://doi.org/10.1109/VISUAL.1998.745285
5. [5]Fatahalian, K. et al. (2010). Reducing shading on GPUs using quad-fragment merging. ACM SIGGRAPH 2010: 'when the scene is tessellated into pixel-sized triangles, a GPU will shade each covered pixel more than eight times.' https://doi.org/10.1145/1833349.1778792

Further reading

• Cline, Lydia Sloan — SketchUp for Interior Design (2nd ed.). Wiley, 2023.
• Akenine-Möller, T., Haines, E. et al. — Real-Time Rendering (4th ed.). CRC Press. ISBN 9781138627000. Reference shelf for the geometry-and-shading chapters.
• Poly Haven and ambientCG — genuinely CC0 PBR material and HDRI libraries (no attribution required). The practical texture source.

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.