[Blender] Cross sections

edited June 2022 in General

Hi and thank you for accepting me in your group!
Is there a script to use only the cross-section system of the Blender-BIM add-on, within a normal .blend file?

Tagged:
Bedson

Comments

  • I think that since the whole BlenderBim add-on relies on the IFC schemas and ecosystem you can't really take advantage of the tools without actual IFC elements and drawing parameters. You didn't specify what your actual needs are so it's a wild guess, but you can try out the default Bisect tool in edit mode. You can use it on multiple objects too.

    (It's bugging out at the end because Suzanne's mesh is non-manifold)

  • Is it possible to select and object, which creates a sectioning Bounding Box around the object?

  • Yes indeed the BlenderBIM Add-on's temporary section cutaway feature works on regular Blender meshes and actually has nothing to do with IFC. The only caveat is that it works using shader tricks, so you have to be in material preview or rendered viewport mode to see the results. It also therefore relies on normals being correct.

    To create a section bounding box, just create multiple sectioning planes. All planes are independent and you can have as many or as little as you want. It might be a nice feature to build a tool where you can create a sectioning box with one click, instead of the 10 clicks it takes right now.

    CoenArEhsanCdimitar
  • You may use collection boolean feature in blender 3.0, basically using whole collection as operand and simple box as cutter. While slower than shader trick, it will provide support for shadows.

    CoenBedson
  • @Moult

    It might be a nice feature to build a tool where you can create a sectioning box with one click, instead of the 10 clicks it takes right now.

    Has there been any progress so far? :-)

  • edited June 2022

    Hi @Coen @Moult
    You may want to try the add-on made for the atlas of anatomy:
    https://www.z-anatomy.com/
    I got the same idea as you and tried to 'stick' (parent) six planes of these on a cube.
    It worked for five of them but I never achieved to have the sixth one.
    It was very close to the solution that you want, though, and I'd be glad if someone could finish it.
    I should still have the file used for the experiment.
    Would you like to try?

    Coen
  • To create a section bounding box, just create multiple sectioning planes. All planes are independent and you can have as many or as little as you want.

    Did you ever achieve to use more than 5?

  • Just curious if anyone found a workflow for modeling detailing in section boxes with BlenderBIM? for example with Revit you could select and object, hit a shortcut key and it would create a bounding box around that object which was a section box. Then the section box was the main pivot/orbit point. It's an extremely useful feature, I used it a lot.

  • @Coen said:
    Just curious if anyone found a workflow for modeling detailing in section boxes with BlenderBIM? for example with Revit you could select and object, hit a shortcut key and it would create a bounding box around that object which was a section box. Then the section box was the main pivot/orbit point. It's an extremely useful feature, I used it a lot.

    For what you want it sounds like isolating the object would work? It's a normal Blender Feature:

    Press shift H with the object selected and it hides the rest of the scene

    It doesn't have a section box but I think it can get you closer to that functionality

  • Thanks, I know about al+H. It's useful, but someone here describes it exactly as I want:

    https://blender.community/c/rightclickselect/W3fbbc/?sorting=hot

    theoryshawAce
  • @Coen hehe I think you know that "someone" :)

    CoenAce
  • edited November 2022

    @Ace said:

    @Coen said:
    Just curious if anyone found a workflow for modeling detailing in section boxes with BlenderBIM? for example with Revit you could select and object, hit a shortcut key and it would create a bounding box around that object which was a section box. Then the section box was the main pivot/orbit point. It's an extremely useful feature, I used it a lot.

    For what you want it sounds like isolating the object would work? It's a normal Blender Feature:

    Press shift H with the object selected and it hides the rest of the scene

    It doesn't have a section box but I think it can get you closer to that functionality

    I join in this reflection. I don't like shift H because it really changes the visibility status of items in the Outliner. I find the § shortcut more powerful because it isolates the selection and zooms in on it, then you can return to the previous view with the same shortcut.
    It would be great to develop this shortcut to behave like Revit's HH, HI (hide/isolate selection) and HC and IC (hide/isolate all elements of the same type as the selection) shortcuts. Finally HR to redisplay everything. I use them a lot and miss them in BlenderBIM

  • There is this add-on that I saw the other day, but I didn't get to test it:

    NigelCadGiruArvcarlopavArEhsanCJesusbill
  • Anyone any experience modeling with alt+b to create sections?

  • @Coen Sure, it is called 'clipping border' and only works in 'solid viewport shading'.
    Super efficient but not editable and there is no way to fill the cut.

    Coen
  • Another addon:
    Section Box

    AceCyril
  • @Coen said:
    Thanks, I know about al+H. It's useful, but someone here describes it exactly as I want:

    https://blender.community/c/rightclickselect/W3fbbc/?sorting=hot

    This looks like the kind of key feature that BIM software just cannot afford to miss. I think it's somewhat sad that Dion's proposal happened 3 years ago and yet there seems that no further movements have been made towards that direction.

    If you're reading this and believe that a proper clipping tool would be awesome for BlenderBIM, please register at Blender Community and upvote the idea. Now it has 87 upvotes, and the most upvoted idea has 669. Let's try to make it through the 100 barrier, every bit counts.

    In addition... it might be worth to set up a bounty specifically targeted to Blender core devs.

    NigelAcebitacovirBedson
  • I find it quite flattering that the Z-Anatomy solution (they gave us a shoutout at a Blender conference) and the Section Box (I assume, it looks almost identical) add-on both actually use the technique developed (and then shared on bA as an independent script) from the BlenderBIM Add-on. Clearly, they have polished it a bit more than us (offering a cube rather than a plane) and offering both mesh boolean vs shader modes. Perhaps it's time to revisit how they've upgraded it, and do more tests on speed (e.g. how does boolean based perform on huge models) and reintegrate those improvements in the BlenderBIM Add-on.

    Does anybody know the Section Box creator and can help reach out?

    Ace
  • What's wrong with the right-click-select idea exactly as you proposed it 3y ago?

  • There's nothing wrong with it, but if it's not implemented, we can still do our best with workarounds and second-best implementations :)

  • In my experience with simple parametric models (eg elongated boxes) the "exact" boolean which is supposed to produce the best results but is also more expensive in terms of performance is OK - slow, but manageable. It does takes a toll with dense objects. The devs also added a feature some versions ago that checks for bounding box collision so if you have thousands of objects that do not intersect with your clip plane or clip box, there is next to no influence on calculations . Bounding box intersection calculations are very fast.

    You'll hit other bottlenecks due to how Blender handles managing and displaying thousands of objects in the viewport alongside slow boolean calculations though.

  • @Moult said:
    There's nothing wrong with it, but if it's not implemented, we can still do our best with workarounds and second-best implementations :)

    But why spend effort on a second-best implementation, when having a closer collaboration with Blender core devs could provide so much more sinergies? Is it really a lost cause? why not setting up a bounty? I'd definitely donate for something like this...

    @Gorgious said:
    The devs also added a feature some versions ago [...] . Bounding box intersection calculations are very fast.

    BVH? That would be great. Could you share any link with more info?

  • I can't find the patch but Howard Trickey is the person you want to talk to (or stalk commits) if you want more information. :)

    This is far, far beyond my area of expertise so I won't be able to offer much information on the topic :p

    cvillagrasa
  • I'd love for this to be done in Blender core but not sure exactly how. Maybe @erik85 knows?

    cvillagrasa
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