Rotating in 3D to match an existing entity without knowing the angle in advance

I am starting to work in 3D and have come to a screeching halt with trying to rotate anything like you can in 2D.

All my drawings will end up in 2D so they can be machined on a CNC machine so when I have a shape derived from an angled section through, say a drinks bottle I need to then rotate that section back to 2D so it matches all the other 2D entities and I can send it to my CNC machine.

I can't for the life of me (I have spent over an hour on this) understand how to rotate a 3D entity about one of its edges/faces so it is facing me in 2D so I can then explode and flatten it to 2D.

Without knowing what the angle is in advance, it seems impossible to me how to achieve this.

The 2D Rotate command is simplicity itself for arbitrary rotation to a known point, but 3D doesn't seem to work the same at all.

Attached is a drawing with an angled 3D Solid with 4 sections on it and I want to be able to rotate the 3D Solid using the front edge so it aligns itself with the vertical red line which is my normal 2D Y Axis.

My perceived workflow would be something like: Select entities, invoke some kind of 3D Rotate command, select the axis or edge or two points I want to rotate along, then pick two further points (in my case the front midpoint of the top face and back mid point of the 3D Solid) and then rotate it up until the back midpoint of the solid is in line with the red line or the midpoint or endpoint snaps have indicated that it is in position (my polar settings are at 45, 135, 225, 270 & 315) so it should snap to the vertical automatically.

Any help or lisp, if this isn't possible in vanilla Bricscad, would be greatly appreciated.


  • Is this what you are looking for?
  • I would also have recommended "Manipulator".

    I grew up with Microstation, 3DSMax, Modo, .....
    And always felt very comfortable with any of their rotate Tools.
    (I want to says that I used and worked already with many different
    Apps and their Tool Setups)
    But to be honest I also did never ever get the same control over
    Bricscad's 2D or 3D Rotate Tools and often failed miserably.

    My main CAD Vectorworks Rotate Tool is very limited and tedious.
    But with some workaround I even can understand and control it.

    The only thing in Bricscad - beside all its great Direct Modeling Tool Set -
    that allows me to do standard 3D Transactions with standard Geometry
    (securely moving along a single Axis, doing Rotations, ...)
    is still only "Manipulator"

    OK, when it goes on to using Manipulator for things like Copying instead
    of just Moving and such,
    I also do not get the correct input cycle or timing ....

    OK, if Bricscad would be my main CAD or only App I maybe would learn
    to use it one day. But so for such (ACAD ?) Tool input sequences are
    far from intuitive for me.
    So I can understand the concerns of the thread starter very well.
  • @Linnemann, thank you for the video.

    I watched it a few times and finally worked out what you were doing.

    The Manipulator needs to align itself with the face that you are rotating and this then allows it to neatly snap to the vertical red line.

    I understand what is needed now.

    The only tricky thing I found was being able to pick up and move the Manipulator without it moving or rotating the entities where it is at present. I have now seen that the Manipulator size can be increased so this is now easier to pick up.

    Thank you for your help, I can now rotate with confidence :-)
  • Hello David

    Youre quite welcome

    It is actually possible to use the normal 3D rotate tool if you want.
    You just need to grab the edge that is intersecting the red line.
    Then you can snap to the endpoint of the red line.

  • I used the align command to achieve this in one step. Am I missing something here?

    Yes, Align is the better or more capable Rotate.
    But also not very intuitive ....
  • You might also consider doing your 3D modeling so that the 3D model is already in the correct orientation for the section to be oriented correctly without having to bother with a 3DRotate command.


  • Thanks for the Align tip that also seems to do what I need.
    @Joe Dunfee In this case I was taking an angled section through some bottle shapes and transferring them to a 2d profile for CNC cutting so I figured Rotation (and Align) were the easiest way of achieving it. I take your point about orientation, presumably this would only apply if I was working solely in 3D?
    Apropos nothing I tried changing the UCS so it was aligned with the angled face and then exported the entities to DXF. I then imported this file into a new 2d file but sadly they didn't come in as a plan view, they were still angled in 3D. Is that a stupid assumption or could something like that work?
  • I use ALIGN constantly - don't know what's non-intuitive about it? It could actually be called MOVEALIGNSCALE because all those can happen in one process. It's inherently 3D - just, when in 2D, you dab Enter twice instead of entering numbers into the 3D bit of it. Brilliant tool!
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