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Rotating an 3D extrusion a certain number of degrees?

May 4, 2013 10:11 AM

Tags: #illustrator #3d #3d_manipulation



I'm trying to figure out how to rotate an extrusion a specific number of degrees. I can easily do it with Isometric views and the preprogrammed Off-Axis views. However, I just chose a random rotation.


In the example below, I made some stairs. Getting them to go in the opposite direction is easy - I just mirror the profile. However, I can't figure out how to properly rotate the stairs 90 degrees.


Does anyone know how to calculate these? I'm sure there's a way, but my brain can't get over it. I'm used to working in 3D modelling software where you can rotate based off a relative plane, not the fixed plane that Illustrator uses.  I've searched everywhere and can't seem to find this specific answer.


Thanks for any help,





Screen Shot 2013-05-04 at 19.10.37 .png

  • Currently Being Moderated
    May 4, 2013 1:24 PM   in reply to mememetx

    Presumably you want the landing to be at the bottom.

    If you turn the drawing upside-down (or stand on your head) do you see what you want?

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  • Currently Being Moderated
    May 4, 2013 6:32 PM   in reply to mememetx

    I just chose a random rotation.

    And that's the problem. In order to make sense out of this poorly-designed feature, you need to proceed in such a way as to keep a mental track of where you started and how you got to the orientation you decide upon.


    This is because the three value fields do not reflect the rotations about the proxy cube's axes, which highlight with seemingly corresponding colors when you mouseover them (which would be far more intuitive and useful). Instead, they reflect the orientation of the invisible "virtual trackball" in which the proxy cube resides. So unless you can do trigonometry in your head as you drag things, the values are pretty much useless. Just yet another example of Illustrator's invariably unintuitive interface design.


    Here is an example of how to proceed. It is not the only way for your example, but one way:


    Before even starting with 3D Effect, I've reflected a copy of the blue staircase cross-section and colored it red. Then I grouped the two so as to manipulate them at once. Upon invoking the 3D Effect>Extrude & Bevel dialog, I set the dialog to Front, effectively zeroing the three values. In this orientation, the Z axis (extrusion depth) is along your line of sight.



    Turn on the Preview checkbox. Click the cursor in the red value field, then tap the up/down arrow keys to increment the tilt of the "virtual trackball" to get the desired bird's-eye (or worm's-eye) elevation.




    Mouseover the vertical axis of the proxy cube, so that it highlights green. Press and hold Shift. Tediously drag rightward until it looks like you have rotated the cube 45°. This is where you begin to encouter the hideous interface. Note that the value shown for the meaninglessly green icon is not 45°. You have to "eyeball" having arrived at the rotation that shows the left and right faces equally.




    Okay the dialog. Copy the Group and Paste In Front. I've selected (white pointer) the pasted copies of the profiles and re-colored them just to differentiate them from the original pair.




    Open the Appearance palette. DoubleClick the 3D Effect that is already applied to the copied Group. Its dialog opens with the same settings that you have already applied. Mouseover the rightmost vertical green axis of the cube and ShiftDrag it leftward until--again, eyeballing it--you have rotated it 90°. Note that the value shown for the stupidly green-colored icon now shows +40. Again, this is because the value shown is reflective of the axes of the "virtual trackball", not of the cube's axes. Clearly the difference between -40° and +40° is 80°, not 90°. But if you rotate the cube to a numerical difference of 90°, it will quite obviously not be a rotation of 90° about the vertical axes of the cube.




    Note also that while you've done this, the blue value has changed. That's the value that the design of the interface suggests is supposed to correspond to rotation about your line of sight. And in fact, if you drag that outer ring, all it does is rotate the whole illustration, as if you were spinning the drawing board. But again, it is showing a rotated value, even though the cube does not appear to have been rotated in that way (i.e.; the green cube axes have remained vertical throughout). Again, this is because the values shown correspond to the useless "virtual trackball," rather than what you're actually interested in.


    You can, by the way, directly manipulate the "virtual trackball" thusly: Mousedown in the black region outside the cube. Press and hold Shift. Drag up/down, left/right.


    Typically hideous Illustrator interface design.



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  • Currently Being Moderated
    May 5, 2013 6:34 AM   in reply to mememetx

    Again, it's a matter of understanding the two points of my previous post: First, that the numbers in the fields reference the "virtual trackball," and, second, that you therefore need to proceed methodically so you don't lose track of how you arrive at the desired orientation.


    Here are the same two Groups (orange/green and blue/red). I've set them both starting with 3D Effect set to the Front orientation, so as to zero all three value fields.



    I've selected the orange/green Group, doubleClicked its 3D Effect in the Appearance palette to open it with its existing settings. I've set the horizontal rotation to 45°. Now bear in mind: By doing this, I'm rotating the "virtual trackball" about its vertical axis, which is currently perpendicular to my line of sight.




    I've selected the blue/red Group, doubleClicked its 3D Effect in the Appearance palette to open it with its existing settings. I want to rotate this Group 90° relative to the orange/green Group. Therefore, I've set its horizontal rotation to -45° (45° - 90° = -45°). This works numerically because I have not yet altered the "tilt" of the "virtual trackball." If I had, then entering a difference of 90 in the green field would not work, because I would be rotating the "virtual trackball" horizontally (relative to my line of sight) from its current orientation, so the other values would be affected and the before/after values wouldn't "add up".


    Now I need to apply the same "tilt" to the two Groups. I reopen the 3D Effect that is already applied to the orange/green Group. I want to "tilt" the north pole of the "virtual trackball" downward toward my line of sight 50°. The exact interaction is important: I mousedown in the black region above the proxy cube. Then I press and hold shift. (It's not shown in the screenshot, but when I do this, the cursor changes to a pair of one-way vertical/horizontal arrows.) Then I drag downward. This way, the tilting is constrained to vertical, relative to my line of sight. As I drag, I watch the red value, and drag slowly downward until it reads 50°. Note that this screws up the green value, but that's okay, because I'm working procedurally and am done with that value.




    I reopen the 3D Effect that is already applied to the blue/red Group, and alter its tilt in exactly the same way..




    I vertically align the two Groups, and they "assemble" correctly.





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