Scale about Center

Scale about Center is very useful for selectively scaling model geometry.  On a PC that's Scale + Ctrl, and for a Mac, Scale + Cmd (when Scale is selected, a tool tip about this modifier shows up in the status bar at the bottom of the screen.)  When Scale about Center is done correctly on a circle, the circle's cardinal points will not be affected.  For more on those cardinal points, check out using Scale tool in conjunction with the Move tool and active Cardinal Points.

Scale about Center allows symmetry to be maintained while adjusting a cylindrical model.  The animation below shows 2 ways the Scale tool can be used by tugging on the diagonal handles.  A single plane can be scaled easily by tugging, entering a ratio in the measurement box or entering a measurement.  A 3D scale operation requires two identical values being entered - ether two ratios or two measurements.  

Note:  The above tutorial switches between face styles for visual clarity.  To see the underlying geometry, enable Hidden Geometry from the View menu.  To enable transparency, switch to X-ray mode: View menu > Face Style > X-ray (this also can be selected though the Style dialog.)   


Twisted Scaling about Center

All the pictured twisty things above are made the same way - by scaling one or more helices wrapped around a cylinder.  The initial helix is made with one of two helix-making plugins.  Drawhelix13.rb (or its updated version Drawhelix14.rb) allows you to make tapered helices centered at the origin.  And helix12.rb will make a helix around any selected face, circle or any profile.  Both scripts are available at the Ruby Library Depot, in the Geometry - Drawing section.


Those helices are welded polylines, acting as a single, multi-segmented Entity.  So they can be selected and manipulated like other geometry.

Original SU Pro forum thread posts with the SKP Tutorials using up this method:
Note:  Otherwise hidden lines may be visible on some downloads.  The top and bottom twisty component edges should be Hidden.  Fix the visible edges by re-Hiding.  Erase+Shift is one way to Hide edges.  OR save the files first to your hard drive instead of directly opening the file.



  • When choosing some initial helix values with the plugin, enter a negative value(s) in the helix plugin dialog box to reverse helical twist.
  • Turn on Hidden Geometry (under the View menu) to see and readily select softened helices.
  • If another construction method is use, resulting in a segmented helix, the helix could be re-welded into a polyline for easy selection and scaling.  Select the segments and use the plugin weld.rb.  There are quite a few other helical construction methods under Tips & Tricks.



Time to Sculpt

Isolated bits of geometry can be shaped with the Scale tool.  The end effect can be similar to some of the results that are possible with the Sandbox's tool, Smoove and Smoove + Shift.  But the Scale tool offers additional sculptural control through its bounding box control nodes.

"Twitching ears"   

It is not particularly important to get all the geometry in the right place when initially blocking out the model.  The position of all geometry - especially when the model is relatively low-poly - is readily adjustable.  

If you are doing a lot of sculpting, adding a 3D navigator will help to make the modeling process feel more natural.  A navigator will let you orbit about the model with your non-dominant hand while working with one of the SketchUp tools with the regular mouse.

In this animation the navigator is orbiting around the model with the left hand while modeling with the right hand.

FYI: The bunny model seen on several of the SketchUp Sage pages initially started out as a mirrored pair of extruded, half-bunny components - like this handle.   To further pose the bunny, the mirrored components were exploded, which caused the center seam to fuse.  Then the bunny turned into a single model which could be further manipulated using many of the techniques demonstrated throughout these Tweaking pages.

Use the sun to sculpt

Usually it is more efficient to disable the sun as that setting will use less computer resources.  But judicious use of the sun will help to highlight poorly positioned faces without needing to orbit to see the problem.

Umbrella handle

Handle  SKP file demonstrating how to form the umbrella handle shown below by extruding geometry with the Push/Pull and Scaling tools.


Grow a leg

Grow a leg  Form human legs by extruding geometry with the Push/Pull tool and scaling stuff.

Growing a tree

Growing a tree uses similar modeling techniques to Grow a leg and handle, except this time the subject is a tree (yup, all sorts of things can be modeled the same way) - the only difference being that the bumps are in different places.  

Some relevant plugins

Note: To download plugins from SketchUcation, join the forum and logon (free). 
  • Artisan  Dale Martens - Sculpting - Fee
  • AutoSmooth ThomThom - Automatically softens and smooths autofolded edges created by the native tools.
  • Bezier Spline Fredo6 - is a steroid-laced bezier curve script.
  • LSS Toolbar  kirill2008 - Adds control construction points to curves and groups with faces for 3D model manipulation.
  • ExtrudeTools - TIG - A set of extrusion tools. 
  • FredoScale Fredo6 -a plugin which adds a lot more functionality in a Scale-like tool
  • HoverSelect  Fredo6 - Multiple selection of lines.
  • Joint Push Pull  Fredo6 - 3D extrusions. 
  • Projection v2  Didier Bur - adds some nifty abilities, like extruding a line along a choosen vector and projecting other good stuff.
  • Nudge  Smustard - Nudges, moves, selected geometry with the keyboard arrow keys. 
  • RpTools  Suite of tools including a move wizard which nudges geometry. Windows
  • Sketchy FreeForm and Deformation  Chris Philips - Deforms a model.  (Updated by TIG)
  • Vertex Tools  ThomThom - A vertex editor - Fee 
  • Tools on Surface  Fredo6 - Draws shapes on 3D surfaces and will make offsets from those new profiles on the 3D faces.