If you've used SketchUp enough to become familiar with the 'Protractor' tool, you know that it automatically orients the protractor cursor-image to lie on a face (or one of the three primary planes.) As long as you ensure that the protractor is oriented upon the face you're trying to measure, picking the origin and two endpoints is simple. The SketchUp Users Guide description briefly mentions the use of the <shift> key while measuring angles with the 'Protractor' tool. The <shift> key will 'lock' the protractor-cursor-image to its current orientation. As long as <shift> is held down, the protractor can be moved to anywhere else on-screen, without the plane of the protractor changing. Using the <shift> key can thus ensure that you are aligned to the face upon which you're trying to measure an angle.
Finding the dihedral angle
A 'dihedral' angle is the angle between two faces. How can a dihedral angle be measured? This appears impossible to new (and even many experienced)
SketchUp users, if they aren't privy to another protractor-orientation 'trick.' While the trick is revealed in the SketchUp Users Guide, it can only be found under the description of the Rotation tool
. The same principle applies, but isn't mentioned in the Protractor section
. Even in the Rotation tool description, it's detailed under the unfortunate title, 'Folding Along an Axis of Rotation.'
The technique works for more than just 'folding.'
Watch this animation a few times to see how to orient the protractor to measure around an axis line. For dihedral-angle measurement, the axis of interest will the be shared edge between the two faces. The trick calls for POSITIONING the protractor at one end of the line, HOLDING DOWN the primary mouse button, and DRAGGING the protractor along the line. Once the protractor 'flips' to encircle the axis line, you can RELEASE the mouse button. The line is now 'locked' as the origin/axis of the protractor measurement. Select the start and end points for the angle, and read the angle value in the Value Control Box (the 'VCB' is in the bottom right-hand corner of the SketchUp window.)
What? The angle in the VCB is an "approximate" (~) integer value? Well, that's not much use. To read a more-accurate angle, you can make a change to the model 'units' setting. Go to 'Window > Model Info > Units' and select an 'Angle Units' precision of '0.000' from the drop-down list. (You can also change the 'length units' precision at this time, if you want.) You can now read angles to three decimal places.
You may have noticed that both the 'Protractor' tool and the 'Rotate' tool use a protractor image for their cursors. The visual distinction between the two is that the 'Rotate' tool has two bold 'half-circle' arrows added to the center.
'Folding along an axis of rotation'
If you want to rotate entities/groups/components around an edge, centerline or other arbitrary axis, see the following animation. The 'trick' to getting the Rotate cursor-protractor to change orientation is identical to the 'drag' method described above for the Protractor tool. To change orientation from the blue (or red or green) axis, POSITION the cursor-protractor over the first endpoint you plan to use for an axis, press and HOLD DOWN the primary mouse button, then DRAG the cursor to the location of the second endpoint. When you RELEASE the mouse button, the axis of rotation will be locked. You've just specified the endpoints of a new axis to use for rotation.
You will note from the animation that you can use this 'drag' method to change the Rotate protractor-cursor orientation, from the blue plane, to the green or red plane. More importantly, you can choose ANY axis for your rotation (as depicted in the animation.) There doesn't even have to be a line entity between your two chosen endpoints.
Note: The <shift> key continues to work as described in the SketchUp Users Guide. (Play with rotations, using the <shift> key, to see what I mean.)
Note: The VCB (Value Control Box) can still be used to enter a precise rotation angle.
Note: The <Ctrl> (PC) key will toggle whether the Rotate tool rotates a copy or the original.
[ TaffGoch ]
Now it's time to play 'wag the tail'...
'Folding Along an Axis of Rotation' is very useful to tweak parts of a model into new positions. And remember, the angular rotation of the rotation protractor becomes smoother the further away the cursor is from the center of rotation.
Note: If a posing rig is used, it can be any shape besides the cross pattern in the animation. A simple line or circle may suffice. Grouping the rig would ensure the rig geometry will not stick to the model geometry. A more complex posing rig shape can be made into a component and permanently saved in a Library for future use in other models.
Tip: If posing rigs are used often on the same model, consider placing the rigs on their own Layer. Then the rig visibility can readily be toogled on and off.
Tip: Consider making each articulation a separate component.
Note: To download plugins from SketchUcation, join the forum and logon.
- AutoSmooth thomthom - Automatically softens and smooths autofolded edges created by the native tools, like the Rotate tool.
- For people wanting to re-position high-poly models which can be made with several distinctive component parts, look into using GhostComp by Fredo6. That plug-in makes simplified, blocky components to be used in place of refined, hi-poly models. That readily allows the smaller ghost component to substitute for the detailed version. Posing rigs can be placed inside the components. The rigs can be assigned to their own Layer to control visibility.
- SelectionMemory2 RickW - This plug-in remembers the last geometry selection set, and allows people to pre-assign a few selection sets. If jointed geometry needs to be tweaked into the perfect position, this plug-in may be useful. Unfortunately the plug-in will not retain selection sets beyond the current SketchUp session. And there is a limited number of selection sets.
A 3D navigator, like those offered by 3dconnexion, allows you to orbit about the model with one hand while the other hand controls a tool with a mouse.
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