AutoCAD Tip: Project 3D to 2D Using FLATTEN

When you need clean 2D deliverables from 3D work, AutoCAD’s FLATTEN (Express Tools) projects selected geometry to your current UCS—fast.

Before you start

• Save a copy of your file. FLATTEN is a geometry-altering step.
• Set the projection plane: use UCS to orient, then run PLAN > Current UCS to ensure a true top-down projection.
• Isolate only what you need to convert (LAYISO) to keep the result lean.
• Confirm Express Tools are installed. If not, update your installation or consult the AutoCAD options available at NOVEDGE.

Core workflow

• Run FLATTEN (type FLATTEN, press Enter).
• Select objects (lines, arcs, polylines, splines, text, dimensions, and many block contents). Note: 3D solids are not ideal candidates—see Alternatives below.
• When prompted “Remove hidden lines?”, choose:
  • Yes for clean 2D documentation with occluded geometry removed.
  • No if you want every projected edge retained for manual curation.
• Wait for completion; large models can take time. Use the command line to monitor progress.

Post-flatten cleanup

• Run OVERKILL to remove duplicates, zero-length segments, and collinear overlaps.
• PURGE and -PURGE REGAPPS to clear baggage and reduce file size.
• QSELECT a few entities and verify Z=0 (Properties: Elevation/Vertex Z). Any stragglers likely belong to blocks or annotative content—explode outliers only if necessary.
• Audit (AUDIT) if you encountered errors during conversion.

Alternatives (often better for solids)

• FLATSHOT (best for 3D solids): Creates a 2D block of the current view with options for hidden/visible line control and layer assignment.
• SOLPROF (layout-based): In Paper Space, generates profile and hidden lines on separate layers from viewport views.
• EXPORTLAYOUT: Converts a Paper Space layout (with viewports) into a standalone model space drawing—great for final 2D issue.
• VIEWBASE/VIEWSECTION (mechanical-style): Parametric 2D views from 3D models, with hidden line and section automation.

Pro tips

• Lock your view before FLATTEN so the projection plane stays consistent.
• Consider a dedicated “2D_issue” layer state and draw-order pass for hatches and annotations after flattening.
• If lineweights look heavy, verify LTScale/PSLTSCALE and plot style (CTB/STB) settings before publishing.
• For repeat workflows, record an Action Recorder macro: LAYISO > FLATTEN > OVERKILL > PURGE to standardize results.

Common pitfalls

• Blocks with mixed elevations may not fully planarize—test with one block first. EXPLODE only if you must, then re-block clean geometry.
• Some curves/splines may tessellate; refine with PEDIT or SPLINEDIT as needed.
• If hidden-line removal seems off, verify you’re in an orthographic “Top” PLAN from the intended UCS.

Need the right AutoCAD configuration or add-ons? Explore options and expert guidance at NOVEDGE, or compare AutoCAD editions here: NOVEDGE AutoCAD.