How to Set the axis of rotation for a component?

[chippwalters]

Are there any good threads or tutes on this. I'm trying to make a robot arm, which can be articulated.

I know about creating hierarchies in the Outliner, I just don't know how to set the axis of rotation for a component. Thanks in advance

-Chipp

[GreyHead]

I don't think that you can set an axis of rotation in native Sketchup - there is no equivalent of joints. That said, SketchyPhysics allows you to use joints to fix axes; and Justin Chin has a 'Rigging Hack' that you can see in an amazing (speeded-up) video here and is explained in a post here .

Bob

[Alan Fraser]

An idea similar to Justin's is to make little rotation "targets" on a separate layer that can be turned on and off. Then the rotation tool will automatically lock onto these, whatever the attitude of the component. When finished, you simply turn off the layer again.

---

rotate.skp

[Gaieus]

You can only use some aiding geometry (like a hidden line or guideline exactly on the axis you want to rotate around) and then force SU to rotate around that. You can even put in sveral such aiding lines into a "joint" to be able to rotate the limbs in different directions for instance.

[chippwalters]

Thanks so much for all the help. Justin's tutorial did the trick. Alan, thanks for the skippy. Gaieus, you're always so helpful.

A sorta related question (not really).
How does one EASILY create a sphere. I know, draw a circle, then rotate a copy of it, and follow me, but the hard part for me is figuring out how to rotate the darn thing! I can always create a box somewhere where I have a flat plane, but there must be a simpler way to get the rotate tool to 'go vertical'....perhaps I'm missing something?

tia,
Chipp

[GreyHead]

I fiddled around with these for a while, then someone here Gaieus? pointed out that there's a standard sphere component in the Shapes folder.

Bob

[chippwalters]

@greyhead said:

I fiddled around with these for a while, then someone here Gaieus? pointed out that there's a standard sphere component in the Shapes folder.

Bob

Doh! (slaps forehead)

Thanks

[Charlie__V]

Chipp,

Also some good info in this video, especially the paper airplane part.

Charlie

[Gaieus]

I think that standard sphere component is based on an only 20 segmented circle though. Be careful with it since you may have alignment problems.

As for defining the axis of rotation:

• select what you want to rotate then the rotate tool
• place your curson on a point that should be on the axis of rotation (this case the origin for instance)
• press (but do not release) the left mouse button and start dragging it along the desired axis of rotation (say the red or green axis or along any existing line, guide line or just in the "air" snapping it to any geometry).
• now release the mouse button, pic a point and start rotating.
  No matter where you get your spheres from, you MUST know this technique for easily defining the rotation axis. In this case my idea about the aiding (hidden or guide) lines may already make sense: you just click on the line, start dragging your cursor along/on it and your are there: a locked axis for the rotation.

[Jean Lemire]

Hi Chippwalters, hi folks.

I posted the following in another SU forum to help someone understand the Rotate Tool so all of this dont necessarily apply to your case:

If you read SU help about the Rotation Tool, you will see, near the
end, an explanation about folding along an axis using the Rotation
Tool.

First, lets go with the definition of a mouse button click. It is a
press of the button and then a release of the same button. This seems
obvious but with SU (and some other software) some actions require you
to press the button AND HOLD IT DOWN while doing some other
manipulations. Many users gets frustrated because they "click, move,
click" while the sequence is press (AND HOLD DOWN), move, release.

In other instances they use "press, move, release" when the proper
sequence is "click, move, click". Like in using the Measuring Tape to
get a measure or to resize a model, a group or a component.

After stating that, lets proceed with some explanations.

---

Normally, with the Rotation Tool, you use these steps:

1 - Select the object to rotate.

2 - Select the Rotate Tool.

3 - Select the plane of rotation (more on that below).

4 - Click to set the center of rotation.

5 - Grab some point on the object to be rotated (click on some point,
line, surface, whatever)

6 - Rotate either freely or by angle increment if the cursor is kept
on the protractor graduations or by snapping to some other geometry or
by specifying the exact angle in the VCB.

7 - Complete the rotation with a click if rotating freely or by
increments or by snapping or by using the RETURN key or the ENTER key
to validate an angle entered in the VCB.

---

Alternatively, you may use these steps:

1 - Select the object to rotate.

2 - Select the Rotate Tool.

3 - Press (dont click, keep it pressed) the left mouse button (LMB) to
set the center of rotation.

4 - Move the cursor along the axis of rotation. The protractor will
then be on a plane that is perpendicular to this axis. If the
rotation axis is parallel to any of the standard axes, the protractor
will use this color (red, green or blue). Otherwise it will be black.

5 - Release the LMB.

6 - Perform the rotation as per steps 5 to 7 of the previous
procedure.

---

How to specify the plane of rotation if you cannot, or dont want to,
specify the axis of rotation:

1 - Draw any face in the required orientation.

2 - Choose the Rotation Tool.

3 - Position the cursor over it.

4 - With the rotation protractor correctly oriented, press and hold
down the SHIFT key to lock the orientation.

5 - While still holding the SHIFT key, move the cursor to the center
of rotation.

6 - Click to set it.

7 - You may now release the SHIFT key.

8 - Proceed as previously to do the rotation.

Please note that the rotation protractor can be forced to align with
all three standard planes:

• red-green plane with a blue protractor;

• red-blue plane with a green protractor;

• green-blue plane with a red protractor.

To do that you may orient the view (with the Orbit Tool) so that the
wanted plane is mostly facing you. Or use any of the standard views
(top, right, front, etc).

You may also observe that in an Iso view or any 3D view that is not
showing mostly the horizontal plane, after you select the Rotate Tool,
if you place the cursor in the bottom two third of the screen, the
protractor is blue, if you move the cursor near the top of the model
window and to the left of the blue axis, the protractor is red and if
you move to the top and the right of the blue axis, the protractor is
green.

Remember that, whatever the method you use to get the correct
orientation, you can lock it with the SHIFT key.

Remember that this orientation trick will also work with polygon and
circles.

Remember that you can zoom, orbit, pan, change scene, change viewing
mode, etc right in the middle of many operation like rotation, move,
drawing, scaling, etc.

I got most of these tips by watching all video tutorials. I strongly
suggest that you watch all the one for version 5 as well since the
basic functions are the same and are not necessarily covered by the V6
tutorials. Pay atention to the commentaries, they are a gold mine of
informations. The downlodable PDF manual is also very usefull. Of
course, the help is the very first ressource you must turn to.

---

For ideas about modeling a sphere, see attached SU file.

---

Sphere_quick_drawing.skp

[2myChaGrin]

Wow, that's a lot of info!. I think the basic issue was getting the rotate tool to flip the circle into position for the follow me tool to do it's thing. I always just hover the rotate tool over a separate vertical surface and hold down the shift key. Hit the CTRL key and find two opposite ends of the circle and flip it in half. Use the follow me tool to make a sphere and then erase the center line. it's that easy.

[remus]

i dont know if you'd find this any easier, but i usually draw 2 circles, one perpendicular to the other and centered on the same spot. i find it a lot faster.

[EinoNuffin]

I've only been using SU for a couple of days but stumbled on this way to arbitrarily set rotate axes to either red, blue or green independent of component axes.
Hover rotate tool top left of screen turns it red +shift locks it. Top right turns it green, lower down default to blue. You can lock and now place the rotate tool onto any model point and rotate as normal.

[Honu]

@jean lemire said:

Hi Chippwalters, hi folks.

I posted the following in another SU forum to help someone understand the Rotate Tool so all of this dont necessarily apply to your case:

.........

I know .. i know we are 10 years later, and still your post was perfect to solve my problem, kudos to you ..