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Lookup tables simple explanation?

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    Lookup tables simple explanation?

    I am a long time Revit user and never had to use lookup tables. I have now done my homework and the only significant difference between type catalogues and lookup tables I can find is:

    1) If a value can be formulaic, or there are only a few relevant parameters use formulas and Family Types.
    2) If a value cannot be derived by a formula or there are a lot of parameters, use Lookup Tables.

    Can anyone please confirm.

    In my understanding if there are a lot of parameters to be calculated on the fly, Lookup Tables are faster. Does anyone have any metrics of how much faster this may be as a % or some other sensible measure.
    Last edited by Balazs; February 11, 2018, 05:01 PM.

    #2
    I didn't have any opportunity to make a type catalogue but when I get one from i.e. pump manufacturer, the family needs to be reloaded every time I want a new type. When I use my own families made with lookup tables, they adapt automatically to pipe diameter (i.e. flange family).
    So I hink it depends on what you want to use it for.

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      #3
      Originally posted by Balazs View Post
      the only significant difference between type catalogues and lookup tables I can find is:

      1) If a value can be formulaic, or there are only a few relevant parameters use formulas and Family Types.
      2) If a value cannot be derived by a formula or there are a lot of parameters, use Lookup Tables.
      Hi Balasz,
      Your two points describe the difference between using regular formulas and using formulas that reference lookup tables. That in itself tells you something: they are both formulas, and one uses a reference. As j_klimek points out, a reference is handy if some relationship needs updating: load new lookup table, done. The table is an integral part of the family file, so I imagine both options are very similar in speed. Unless you write a very complex formula or use a very large lookup table.

      What is missing in your points is how both these approaches compare to a Family Type Catalogue. Those come in to play just once, on loading the family into the project. They are not referenced at any other moment. That makes a family use less computational resources, I suppose. It also means that you have complete freedom in altering any of the values. A bit like the freedom to smoke, drink alcohol or any number of fun, inadvisable activities: not always a good thing.
      There must be a better way...

      Ekko Nap
      Professional nitpicker, architect, revit consultant, etc.

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        #4
        Perfect. Thank you.

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