Author Topic: Revit simple formula list for parameters.  (Read 1105 times)

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Lonnie

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Revit simple formula list for parameters.
« on: July 12, 2021, 11:01:28 AM »
I've been doing some pretty simple formula's and they've been kicking my butt. I was wondering if someone had a nice cheatsheet for simple things like

Turning a number negative.
making sure the input is taken in inches instead of default project units (Feet.)

I don't do anything fancy and I don't do them often. I just want something to refer to.

The reason this came about (I am just using this as an example of the most complicated thing I typically do.) is I need a formula to solve for number of sensors, the distance between sensors and the coverage of sensors. Sensor is in magenta area of coverage is the cone attached.

What drives that is.
Length between arms. (There can be no overlap.) The sensors have a 14% growth so the further apart they are the bigger the cone.
Arm Length. (The arm can be anywhere from 8" to 32" in length.)

Perhaps these two jpgs will help.
Scanner 1 is a visual of some parameters.
scanner 2 is shows the formulas I am doing. (note I am still working on them. They are very very rough.)




« Last Edit: July 12, 2021, 12:20:19 PM by Lonnie »

JohnK

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Re: Revit simple formula list for parameters.
« Reply #1 on: July 12, 2021, 11:47:03 AM »
One of those things that has always been on my TODO list. Formulas are a pain in the butt sometimes and you often find yourself negating units just to get things to work.

I've found this one fairly nice:

https://www.revitforum.org/node/1126

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Lonnie

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Re: Revit simple formula list for parameters.
« Reply #2 on: July 12, 2021, 12:21:48 PM »
Thank you!

It's way overkill for me but much much better than the ones I've found.

JohnK

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Re: Revit simple formula list for parameters.
« Reply #3 on: July 12, 2021, 12:37:43 PM »
Oh I just did one of those exact same formulas/situations (coincidence).

The more complicated type formulas will drive you nuts! -e.g. I had to calculate the air velocity from a rectangular opening (not complicated in excel) but revit is so effed in the head I found myself making up formulas and using constants I don't think really exist.
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Lonnie

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Re: Revit simple formula list for parameters.
« Reply #4 on: July 12, 2021, 01:39:50 PM »
No lie!! :tickedoff:

When I have to think about it I write formula's out in notepad++ and paste them into the parameter just to keep track of what I am doing. Make notes and such.
« Last Edit: July 12, 2021, 02:29:18 PM by Lonnie »

JohnK

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Re: Revit simple formula list for parameters.
« Reply #5 on: July 12, 2021, 02:26:45 PM »
That is a very good idea for another reason you may not know about; revit will change the formula as it evaluates it. As an example Try to make something unitless  but dividing by 1.

You may have a dimension type parameter and if you type something like: " Length / 1 " will get changed to " Length / 1' " ...not that big of a deal in most cases but when you start converting/using constants/etc. in more complicated formulas you'll get some weird numbers and overrides after revit starts evaluating your formula and "fixing" it. ...I hate revit parameter formulas.
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