G—P / FMX 430 / Semester / Week 04

Week 04 · Phase 2 — Building at true scale · Twinmotion, session 2 of 2

Introduction to Twinmotion II: Datasmith into Unreal

Session two of the introduction to Twinmotion. Last week you learned the tool in a model that was already built. Today your own house comes in from Blender, gets checked against its drawings, and then leaves: through Datasmith into Unreal, onto the globe at its real address, and in front of a camera. Moving geometry between tools without mangling it, then photographing it like a client is paying, is the most employable skill of the semester.

Session Fri Sep 25 · 10:00 am – 1:50 pm · CCB-134 Bring your house massed in Blender at 1:1 and exported as FBX, its dimensioned plan and section, and the site's coordinates
By the end of this session you can

10:00 · Brief Other people's geometry

The archviz pipeline is a translation problem. Architects work in CAD and BIM tools that care about tolerances and revisions; game engines care about triangles, UVs, and frame time. Datasmith is Epic's translation layer — it carries geometry, materials, hierarchy, and metadata from those worlds into Unreal, and Twinmotion sits on the same foundation as the fast, designer-friendly front end. Project 2 (see the Projects tab) lives in this pipeline until the Week 6 crit. Your geometry makes two trips today: Blender into Twinmotion, then Twinmotion into Unreal. Scale can break on either one.

What Datasmith preserves — and what it can't

Expect the scene hierarchy, instancing, and material assignments to arrive largely intact; expect to do surgery on everything a CAD tool never had to think about. The reliable wound list: object names like Extrusion_2847, no collision anywhere, lightmap UVs missing or overlapping, pivots at the world origin instead of on the object, and glass that imports as a gray slab. None of these are bugs — they're the difference between a drawing and a game engine. Budget for cleanup; the brief's "pipeline notes" deliverable is exactly this ledger.

Archviz is photography

What a client buys is not the model — it's the image. Which makes this week secretly a photography class: eye-level cameras (not drone-hovering god views), verticals kept vertical, wide but honest lenses in the 18–35 mm range, and depth of field used to direct the eye rather than to show off. In UE that language lives in the Cine Camera Actor, with real-world focal lengths and apertures, and in 5.8's rendering path for stills and flythroughs with accumulated, film-quality depth of field.

Scan versus model

The industry's live question, and this week's discussion: capture is getting so good that sometimes the right move is to not model at all. That's where Gaussian splatting comes in.

State of the Art · Scan vs. model — Gaussian splatting

3D Gaussian Splatting (Kerbl et al., SIGGRAPH 2023 — this course's landmark paper) renders captured reality at 100+ fps and is now the fastest-growing capture method, entering UE through plugins like Volinga and NanoGS (no first-party Epic support yet). LiDAR and photogrammetry still own measurement. Discussion: for an archviz client, when do you scan, when do you model, and when do you combine?

Kerbl et al. project page · Splats in UE, 2026

10:45 · Guided lab Blender → Twinmotion → Unreal → camera

Everyone runs the same pipeline end to end today, on their own house. If your massing is not ready, run it on the Lakehouse Retreat from last week and repeat it on your house in the workbench hour.

  1. Bring your house into Twinmotion

    Import the FBX you exported from Blender. Before anything else, repeat last week's two checks: measure a door opening and the slab-to-slab height against your drawings, and stand a human figure in the doorway. If the house arrives a hundred times too large or too small, the fix is in Blender, in the port contract, and not in a scale field here.

  2. Dress the scene in Twinmotion

    Spend twenty minutes doing what Twinmotion is best at: one or two honest materials, furnishings from Fab, vegetation, and the location, date and hour of your real site. Note how fast iteration feels — that speed is why the pipeline starts here.

  3. Export for Unreal

    Export the scene from Twinmotion as a Datasmith file (via its export options for Unreal / Datasmith). Note what the export dialog offers to include — that list is exactly what will and won't survive.

  4. Enable Datasmith in UE

    In a fresh UE project (FMX430_Archviz — zip a clean dated copy before anything is imported): Edit → Plugins, enable the Datasmith importer plugins, restart if prompted.

  5. Import and inspect the damage

    Import the Datasmith file from the main toolbar's Datasmith import. Then inspect like a surveyor: open the content browser folders it created, check names, select meshes and look for collision and lightmap UVs in the static mesh editor. Write down the top five problems — this list drives the AI lab.

  6. Fix a few by hand first

    Rename a handful of assets properly, generate collision on one mesh in the static mesh editor, fix one material assignment. You need the manual feel for each fix before you delegate it at scale.

  7. Site it on the globe

    Work in a georeferenced level, set up as in Project 1. Set the Cesium georeference origin to your site's latitude and longitude, place the imported house on the terrain, and rotate it to its true orientation. Then set the sun to the same date and hour you chose in Twinmotion. Sited, not floating: real neighbors, real ground, a matched sun.

  8. Shoot a hero still

    Place a Cine Camera Actor at standing eye height. Choose a focal length deliberately (start near 24 mm), level the horizon, compose with foreground. Set aperture and focus distance in the Details panel so depth of field serves the composition. Render a high-resolution still.

  9. If there is time, block the approach shot

    Rough out a 20–30 second camera move through the space (Sequencer basics on the projector — full cinematics come later in the course). Slow is professional; fast is a video game trailer.

  10. Back everything up

    A dated zip on your cloud drive, with your import problem list saved alongside — it's the seed of Project 2's pipeline notes.

12:00 · 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. Finish the lab on your own work

    The guided lab was built on the class example. Now do it on the piece you are actually submitting. That second pass is where it sticks.

  2. If you fell behind, catch up here

    This is what the hour is for. Say so and I will come to you — do not spend it quietly stuck.

  3. If you are ahead, go deeper

    Take the optional extensions from the lab, or push the piece further than the brief asks. Nothing graded depends on them.

  4. Ask 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

1:15 · Crit / share Hero stills

Everyone puts their one hero still on the projector. We read them as photographs: where does the eye go, are the verticals vertical, what is the depth of field for? Then each house gets one question: is it the right size, and how do you know? Materials are next week and lighting the week after, so the house needs to be in Unreal and on its site by then.

Homework — due before Week 5

TaskDeliverable
Finish modeling your house in Blender — every wall, opening, slab and column the drawings show — and run it through the whole pipeline again.Datasmith import in your archviz project, sited at true coordinates, plus your import problem list.
Choose the furnishings the house needs from Fab, and check each one for scale.Assets placed in the Twinmotion scene, with license and creator noted in your process log.
Read the Gaussian splatting project page (abstract and results at minimum).Three sentences in your log: a case where you'd scan instead of model, and why.

Resources