IfcElementQuantity in the BlenderBIM add-on

I was trying to assing some quantities to different IFC elements, and I have collected some questions:

Why is there no 'NetSideArea' for IfcSlabs ? Because now the BlenderBIM add-on appears to quantify the whole surface of the IfcSlab. Maybe I am doing something wrong?

Because when I select a IfcWall, 'NetSideArea' appears in the BlenderBIM add-on

But validating this calculation in BIMVision is making me doubt the amount of the net square meters

More a general question,
What would be a fast workflow to quantify an IFC file?
Is it possible to calculate all the NetSideArea of an IfcSlab or IfcWallStandardCase in one go?
How does the calculation even work? It calculates it from Blender geometry of IFC geometry? It's a really nice and impressive feature though.

Comments

  • edited January 19

    I imagine because it's not typically a quantity you need for slabs? When calculating formwork you're generally only interested in the top/bottom area of the slab, and usually all your historical unit rates for slabs (including for scheduling purposes) will be based on m2 of top area.

  • edited January 19

    @vpajic

    I imagine because it's not typically a quantity you need for slabs? When calculating formwork you're generally only interested in the top/bottom area of the slab, and usually all your historical unit rates for slabs (including for scheduling purposes) will be based on m2 of top area.

    Defintion of NetArea:

    Total area of the extruded area of the slab. Openings and recesses are taken into account by subtraction, projections by addition. Only given, if the slab is prismatic.

    Yes indeed, but when you look at the first picture of the BlenderBIM screenshot, you see it calculated 159.35m2 for this IfcSlab, when I measured the top plane of the IfcSlab in BIMVision it says 76.884m2.

    Just had another idea, can the dimension calculations from the viewport overlay be used to write the calculated dimension to a PropertySet?
    As you can see here it calculated it in mm2? any way to convert this to m2 and get this quantity through the python api?

    My dream scenario would be that the user can select faces/edges in BlenderBIM just like in BimVision, then saves the selection and writes to them an IfcPropertySet, this way the user can make very quick precise scheduling quantities. It would work well with the BlenderBIM spreadsheet obviously.

  • edited January 19

    I really like the idea of that, but the specifics on how it works would need to be explained by Dion. A few months ago I had the idea of creating an OS python library for the sole purpose of calculating norm-conformant quantities ( think VOB, SMM7, ÖNORM etc.). Unfortunately, I quickly realized that this would be an order of magnitude more difficult than my current skillset can cater for 😞.

    Currently, the only software on the market that I've seen and used that can a) calculate correct+detailed quantities and b) display the calculation steps in a way that can be audited is iTWO, the software from RIB. This is unfortunately a software that also makes the interoperability issues from Revit seem like nothing! Even exchanging files within the software can be an absolute nightmare, but I don't want to rant about that now 😁.

    Perhaps my coding skills reach a point where this project could become viable - Maybe your'e also interested in working on something like this?

    Coen
  • btw - have you tried just adding the quantity set to your objecting and then clicking on guess quantity? maybe that serves your purpose?

  • @vpajic

    btw - have you tried just adding the quantity set to your objecting and then clicking on guess quantity? maybe that serves your purpose?

    Yes, I've been using quess quantity extensively. :-)

    Does the "Copy Property to Selection" button do anything? When I click it nothing happens, and when I click on "Edit Source" like you taught me ;-). I get a notification 'see text editor'. I also see nothing in the System Console.

    Regarding your other post:

    think VOB, SMM7, ÖNORM etc

    I have no idea what all of this is. Austrian/German standards/norms?

    Perhaps my coding skills reach a point where this project could become viable - Maybe your'e also interested in working on something like this?

    Why not? :-D. My personal interests is in making the BlenderBIM add-on facilitate small business owners who are not able to spend enormous license fees for BIM software like big corporations. Really would like to see the BlenderBIM add-on to be able to produce drawings in a user friendly manner :-)

    I quickly realized that this would be an order of magnitude more difficult than my current skillset can cater for

    That means there is still so much to learn and to look forward to. :-D

  • Does the "Copy Property to Selection" button do anything?

    This copies the property over to selected objects. Once you click on "Edit Source" you need to open the Scripting tab or open the Text Editor . If you have no other scripts open then you just need to click on the button below: The code will then automatically on the line which calls the operator you're referring to:

    I have no idea what all of this is. Austrian/German standards/norms?

    VOB is german, ÖNORM is austrian, SMM7 is from the UK. Many countries have their own standards. In essence they dictate how construction work should be described and quantified etc. It serves as a standard for the industry and facilitates the fair comparison and validation of tenders, compensation for work done and more. As far as quantities go though, in my humble opinion they do more harm than good. I feel the industry should transition to net-quantities , as this is the only concept that can be translated 1x1 across languages and projects. As it stands though, you have complicated conditions for how certain quantities should be calculated, how to round, how to subtract etc.

    That means there is still so much to learn and to look forward to. :-D

    😁😁 I agree wholeheartedly, but how does one find the time when one is also interested in reading, in riding motorbikes, in fitness, in raising their child 😂. Perhaps we should focus on a medical solution to somehow bypass the need to sleep!??

    CoenCadGiruVDobranov
  • @Coen Did you find a way to add additional properties to a Qset? There is a NetTopArea value that can be used to calculate the area you're after but i dont know how to add it as part of the Qset.

  • @Coen @ChubbyQuark hey, just an update that could be useful.
    We are (slowly) implementing a better qto calculator. It's already available for walls, slabs, beams, columns, doors and windows.
    For now, if the calculating function is implemented, it appears a square icon near the guess quantity button, in the Qto_Pset edit panel.
    In the future, all can be automated (at least, it's my goal).
    It would be helpful to have feedback on that, so if you want to try with the files showed at the beginning of this post, it would be nice :-)
    Btw, note that the difference between NetQuantity and GrossQuantity is the presence of IfcOpening/Void and make sure to have last development version of bbim.
    Cheers, Massimo

  • Hi Massimo, sounds good. Im having a similar issue to Coen where NetArea is calculating both sudes of an .ifcCovering object. Its a mesh I have modeled via the blender UI to represent a floor covering so would expect just one side to be calculated for net area by default? Will post some screen grabs in a bit.

  • The area shown on the floor is the blender calculated mesh face. Net top area matches this and is the area you would expect for a covering, i.e. paint, render, gypsum board, floor finish etc. When NetArea is calculated it calculates total mesh surface area. Is there a way to add Net top area to the Qset or should NetArea only calculate the outer face maximum total area?

  • @ChubbyQuark could you share the .ifc file?
    I can implement calculating function for IfcCovering so the Qto_ quantities can be more accurate

  • Sure, here is the file. Looking to create a floor finish plan from the model, hence the need for area quantities.

  • @ChubbyQuark ok, i just added the calculating function for IfcCovering so update your BBim with the last developer version and i'll find this button

    Feel free to send me feedback about calculated quantities.
    Cheers, Massimo

    ChubbyQuarktheoryshawtlang
  • Amazing, thanks Massimo. Ill get the latest build and continue with the drawing pack. Hoping to get GAs, floor finishes, elevations and sections from the model so will feedback as i work through.

    Is it possible to count the number of ifcElements of a specific type and total them? I think Coens spreadsheet addon does this but wasnt sure if it is possible within the BlenderBim ui?

  • @ChubbyQuark i'm glad it helped you :-)
    Btw, i don't know if there is a way to count elements in the Blender UI

  • Works perfectly. Calculations for Gross and Net areas when voids are added are correct too :)

    CoenMassimo
  • Hi again, one you may already be aware of is the method 'Calculate' and 'Guess' quantities calculate width. Guess uses the x dimension while Calculate uses the z dimension of the element.


    Massimo
  • @ChubbyQuark this is because calculate method follows the ifc Qto_CoveringBaseQuantities definition of width.
    If you look at it (look at the schema or right click on the property and click on IFC definition) you will see that the width (for covering) is the depth.
    Guess quantity function just tries to guess the quantity.

  • I wondered if it was related to how the schema expected the property. Once depth and height is available I assume the relevant value can be accessed, if required?

  • @ChubbyQuark sorry but i don't understand what you mean...

  • edited November 20

    I might be wrong but I assumed that width, length and depth could all be exposed for covering elements, similar to slab elements? I'll check the schema...

  • edited November 20

    @ChubbyQuark if i understand correctly, IFC schema provides width, length and depth for an IfcSlab element.
    The decision about what has to be defined into the file is up to the user, so for example an IfcSlab element can has got only the width and another element can has got width, length and depth.
    Calculator and guess quantity functions only help to calculate the quantities.
    IfcSlabs and IfcCovering btw use the same conventions in the schema, so the width quantity has the same meaning

  • That makes sense. How are the width and length added for calculation? I don't see them as available in the Qto UI?

  • @ChubbyQuark i'm sorry, i was confused bc i'm on mobile phone and i didn't check.
    IfcCovering class has got only width, netarea and grossarea.
    The sentence i wrote above is for IfcSlab that has width, length and depth.
    Now i rewrite the sentence so people won't get confused.
    So, regarding your last question, following the schema, an IfcCovering element can't have a length or depth quantity defined.
    Of course, you can add another Property Set with these quantities, but it wouldn't be standardized. In this case, also, it's not possible to use the qto calculating function in object panel, but maybe the qto panel in n-panel can be helpful.

    ChubbyQuark
  • edited November 20

    Great, thanks for clarifying. I thought i was missing something. Good to know these can be added if needed.

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