Rhino - Import — David Barbarash

Why this matters

A CAD import into Rhino produces a flat dump of all geometry at whatever coordinate position your CAD file used. That geometry may be miles from the origin, scaled incorrectly for Rhino's unit system, full of duplicate curves, and organized under CAD layer names that don't serve a 3D modeling workflow. The cleanup sequence below gets you from raw import to model-ready in one focused session.

Import sequence

Step	Command	What you're doing
1. Set units	UNITS	Match Rhino units to your CAD file. If your CAD drawing is in Architectural units (inches), set Rhino to inches. Mismatched units produce a model that is 12× too large or small.
2. Import	File → Import (or drag .dwg into viewport)	Import your cleaned CAD file. Choose the Top viewport first — all CAD linework should arrive as flat curves on the XY plane.
3. Zoom extents	ZOOM then E	Finds and frames all imported geometry. If nothing is visible after import, this is always the first step.
4. Check position	PO — click a known point	PO places a point object at the clicked location and reports its XYZ coordinates. If your model is at X: 2,450,000 Y: 480,000 (real-world survey coordinates), you need to move it to the origin.
5. Move to origin	M — click base point — type 0,0	Select all geometry, MOVE, click a consistent reference point (a site corner, the intersection of key lines), type 0,0 to drop that point at the origin. This prevents modeling precision errors that compound at large coordinates.
6. Verify scale	DI — click two known points	DIST measures between two clicks. Measure a known dimension from your CAD drawing (a road width, a building footprint dimension). If it doesn't match, your units were wrong. Fix units and re-import.
7. Organize layers	LA — create "CAD Linework" parent layer	In the Layers panel, create a parent layer named "CAD Linework." Move all imported CAD layers into it. This keeps imported linework organized separately from your new modeling layers.
8. Remove duplicates	SELDUP / SELDUPALL — Delete	Selects duplicate curves that OVERKILL may have missed. Delete them. Do this per layer.
9. Find bad objects	SELBADOBJECTS	Selects any geometry Rhino considers invalid. Bad objects cause modeling failures. Fix or delete them before proceeding.
10. Fix bad objects	INVERT → HIDE → X (Explode) → JOIN → SELBADOBJECTS	Invert the selection (to select only good objects), HIDE them, leaving only bad objects visible. Explode the bad objects into components and rejoin them. Check again with SELBADOBJECTS. Redraw anything that cannot be fixed.
11. Restore hidden	SHOWSELECTED	Brings all hidden objects back. Your model should now show only cleaned geometry.
12. Purge	PU	Removes unused blocks, materials, and layer definitions left over from CAD. Keeps the Rhino file clean before modeling begins.

Image Placeholder

Screenshot: Rhino Layers panel showing a "CAD Linework" parent layer with all imported CAD sublayers nested underneath it, clearly separated from the new modeling layers above

Layer organization for modeling

Once cleaned, rename and reorganize layers to match your modeling plan. Rhino layer names mirror the CAD naming logic but use 3D modeling descriptors rather than 2D drafting ones. Your CAD layer L - Walk becomes the modeling layer for the walk surface geometry. You'll create new layers for terrain, terrain mesh, split surfaces, and modeled 3D elements as you build the model.

Assign a unique material to every layer before starting LiveSync. Lumion uses Rhino layer materials as material IDs — if two layers share the same material, they arrive in Lumion as one material and cannot be independently assigned. A flat color per layer is sufficient at this stage.

Try this

After importing your CAD file and moving it to the origin, type DI and measure three things you know the dimensions of from your CAD drawing: a building width, a path width, and the distance between two site corners. All three should match. If any one of them is off, you have a units problem that will cascade through every modeling decision. Fix it now.

What breaks

Not moving to the origin — Rhino maintains floating-point precision that degrades at very large coordinate values. A model at survey coordinates (millions of units from origin) will produce modeling errors, display glitches, and Boolean failures that are invisible at normal zoom but compound over time. Always work at or near the origin.

Skipping SELBADOBJECTS — bad objects look fine on screen but fail silently during modeling operations. SPLIT will not work correctly on a bad curve. JOIN will not complete if a bad object is in the selection. Find and fix bad objects immediately after import, not after spending an hour on terrain.