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Revit Shadows/ Sun Settings Incorrect - WorldWide!!!

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    #1

    Revit Shadows/ Sun Settings Incorrect - WorldWide!!!

    (well - almost worldwide if you have daylight savings time)
    I found this disconnect over a decade ago (and duly reported it) - since its still there I thought Id better bring it to everyones attention again. (theres heaps about it through google).
    Heres the problem:
    Under the Sun Settings (or Manage/location) there is a check box for "Use Daylight Saving time" (Note this is a project wide setting)
    daylightsavingstime.png
    One would expect everyone to have this ticked so that when they do their sun/shadow studies it will show the correct shadows at any time of the year.
    Wrong.
    Its not tied into any daylight savings time based on where your project is.
    As far as I can tell, all it does is move the clock Revit uses to base it shadows on one hour backwards for anytime/any date of the year.
    This means that (remember its a project wide setting) either:
    1. If its ticked anydate that falls outside of your daylight savings time will be one hour out.
    2. If its not ticked anydate that falls within your daylight savings time will be one hour out.

    Heres my quick test: note that daylight savings here in NZ is between ~October and ~April. Therefore with my shadows set for 2pm, 12th August - there should be no difference in the extent of the shadow if the checkbox is ticked ot not.
    Incorrect shadows.PNG

    Nasty
    Last edited by Alex Page; August 12, 2020, 07:39 PM.
    Alex Page
    RevitWorks Ltd
    Check out our Door Factory, the door maker add-in for Revit
    Tags: None
    #2
    Originally posted by Alex Page View Post
    As far as I can tell, all it does is move the clock Revit uses to base it shadows on one hour backwards for anytime/any date of the year.
    Hi Alex,

    Yup, that's how we use that tickbox, knowing that the time is in summer time, we should tick it and if it is not, to not tick it. I think that's how its always been and how we've always used it.

    What you're suggesting is that Revit taps into some worldwide database, checks the site location, then checks whether the date put in is in daylight savings time and then applies DST or not as necessary. A bit much that, no ? Timeanddate.com ?

    Based on recent conversations, I think there's a LOT of other stuff Autodesk's boffins could spend their time fixing instead
    Last edited by kamranmirza; August 12, 2020, 08:17 PM.
    Kamran Mirza
    Chartered Architect RIBA, ARB, PCATP

    Comment

      #3
      HOWEVER, having said that, how does it work when you are doing a sun study for various dates across the year ?

      Do you run it once with the DST ticked and then once again with it unticked and delete all the ticked winter results and all the unticked summer results ? Hmmm.
      Kamran Mirza
      Chartered Architect RIBA, ARB, PCATP

      Comment

        #4
        Exactly:
        The problem is if you are showing multiple sun studies in the same project (they may even be on the same sheet) one of them will be incorrect if you dont realise you have to change the hour to, say, disclude daylight saving before printing different aspects of studies. In fact - even if you know - does everyone in your team know not to print without checking/changing that setting? This is just asking for errors
        I cant see it being too hard to programme (not that Im a programmer):MS Windows knows what time to report.

        Kamran - to me its a case of, without realising it, a firm could get in a very nasty place in regards to getting approval to build a building/house based on those shadow diagrams when they are extremely easy to get wrong because of that logic disconnect.
        Last edited by Alex Page; August 12, 2020, 09:06 PM.
        Alex Page
        RevitWorks Ltd
        Check out our Door Factory, the door maker add-in for Revit

        Comment

          #5
          2020_0813-SunSettings.PNG
          I have the Daylight Savings check box off always.
          In my Sun Settings dialog I have entries for all the times of day and month I wish to show shadows, but retard the summer solstice times by one hour.
          So, in the instance above:
          1221 - 0700 - standard time
          means:
          December 21, 7am, which is 8am summer time.
          Last edited by anthonyB; August 12, 2020, 11:18 PM.

          Comment

            #6
            Yep - good idea. Thats what I do as well: just worried about people who dont know that the daylight savings checkbox may give incorrect results
            Alex Page
            RevitWorks Ltd
            Check out our Door Factory, the door maker add-in for Revit

            Comment

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