topic Re: Bounding Box Functionality in Revit in Revit API Forum

Bounding Box Functionality in Revit

mizrachi_amir2 — Fri, 26 Apr 2024 21:56:21 GMT

Hello,

I am trying to figure out the functionality of the Element Bounding Box in Revit.

I created a 100mm thick wall, length 880mm.

in top view, I placed the bottom-left edge of the wall in PBP/SP/Internal Point which is in 0,0,0:

In this case I was expecting to see that Min XYZ point is 0,0,0, while MAX XYZ is as-is (2.887 feet = 880 mm, 0.328 feet = 100 mm). But actually Min param shows some other value.

Can someone explain what am I missing here and how does that actually work in Revit?

Thanks 🙂

Re: Bounding Box Functionality in Revit

Moustafa_K — Sat, 27 Apr 2024 05:01:08 GMT

the minimum value that you see represents a very small value close to zero. In scientific notation, the number is expressed as the product of a coefficient and a power of 10. In this case, the coefficient is -2.82696...., and the exponent is -16.

When the exponent is negative, it indicates that the decimal point is shifted to the left by that number of places. So, in this case, you would move the decimal point 16 places to the left, making the number extremely close to zero.

In short, you may consider numbers with negative Exponent as zero, or very very close to zero if you want to be precise.

hope this helps

Re: Bounding Box Functionality in Revit

mizrachi_amir2 — Sat, 27 Apr 2024 05:07:21 GMT

Thank you, @Moustafa_K.

I missed that exponent. But still why I don't see a complete zero value, but one very close to zero? Is this how Revit behaves?

Re: Bounding Box Functionality in Revit

Moustafa_K — Sat, 27 Apr 2024 05:12:53 GMT

that would be a very long discussion to explain, but briefly it's common to encounter values that are very close to zero instead of a complete zero, particularly when dealing with floating-point numbers. This is due to the way floating-point numbers are represented and stored in memory. you need to know this behavior is not specific to Revit but is rather a fundamental characteristic of how floating-point arithmetic works in most programming languages and environments.

Re: Bounding Box Functionality in Revit

mizrachi_amir2 — Sat, 27 Apr 2024 06:00:28 GMT

Thanks again!
Another question in that manner that popped up to me - why do I get different Z values in Bounding Box of a wall in 2D view vs. 3D view?

Image for instance for a single wall:

Re: Bounding Box Functionality in Revit

Moustafa_K — Sat, 27 Apr 2024 06:57:34 GMT

When you supply a view as an argument to get the a Boundingbox of an element, the returned boundingbox value is trimmed to the bounds of the view i.e. View.CropBox.

For example, if you draw a wall that has a height 8 meters and placed on Level 0, and your project is 2 levels, [L0, height 3] , [L1, height 5]

Getting the boundingbox of the wall in L0 will return a BoundingBox of minimum Z = 0 and maximum Z = 3

and typically for L1 would be minimum Z = 3 and max Z = 8

and if you provided null, this means no trim, the you will get minimum Z = 0 and Maximum Z = 8

hope this simple explanation helps