SketchUp automatically creates a Face when Edges meet certain conditions.
When a Face fails to form it’s because one or more of the conditions haven’t been met.
• The Edges must form a closed loop.
• All the Edges must be coplanar.
• No stray Edges, coplanar with the closed loop, project inside the loop.
• The Edges are not too short, say <.002" in length.
If you inadvertently delete a Face you can heal the Face by simply tracing one of the bounding Edges, endpoint-to-endpoint with the Line tool.
Creating faces in a 2D CAD import can be problematic due to minor errors in the CAD linework.
Here’s a collection of handy plugins for CAD import cleanup and the typical order in which they’re used.
- Repair gaps and lonely edges using Edge Tools²
- Run MakeFaces
- Cleanup stray lines
Installing Ruby Plugins (Extensions) — SketchUp Help
https://help.sketchup.com/en/article/38583
Edge Tools² by ThomThom
http://extensions.sketchup.com/en/content/edge-tools²
*Edge Tools requires a supporting plugin, TT_Lib²
TT_Lib² by ThomThom
http://extensions.sketchup.com/content/tt_lib²
Once the edges are repaired, run MakeFaces.
MakeFaces v.1.400 by Todd Burch
*MakeFaces requires a supporting plugin, Progressbar.
ProgressBar v.1.000 by Todd Burch
Once faces are created, you can try cleaning up a bit more with these…
CleanUp³ by ThomThom
http://extensions.sketchup.com/en/content/cleanup³
*ThomThom’s CleanUp³ requires the same supporting plugin as his Edge Tools, TT_Lib²
TT_Lib² by ThomThom
http://extensions.sketchup.com/content/tt_lib²
StrayLines v.1.000 by Todd Burch