topic Re: Find Centroid of wall in Revit API in Revit API Forum

Find Centroid of wall in Revit API

BBKENGJS — Sat, 11 Feb 2023 03:19:07 GMT

Please help me with this code. I can get some elements selected in Revit, filter only wall, but I have problem to move from selected ID's of walls to solid so I can use the ComputeCentroid.

<Autodesk.Revit.Attributes.Transaction(Autodesk.Revit.Attributes.TransactionMode.Manual)>

Public Class GCentroid

Implements IExternalCommand

Dim _uiApp As UIApplication

Dim _uiDoc As UIDocument

Dim _doc As Document

Public Function Execute(commandData As ExternalCommandData, ByRef message As String, elements As ElementSet) As Autodesk.Revit.UI.Result Implements IExternalCommand.Execute

Try

' Select some elements in Revit before invoking this command

Dim uidoc As UIDocument = commandData.Application.ActiveUIDocument

Dim selection As Selection = uidoc.Selection

Dim selectedIds As ICollection(Of ElementId) = uidoc.Selection.GetElementIds()

If 0 = selectedIds.Count Then

TaskDialog.Show("Revit", "You haven't selected any elements.")

Else

Dim info As [String] = "Ids of selected elements in the document are: "

For Each id As ElementId In selectedIds

info += vbLf & vbTab + id.ToString

TaskDialog.Show("Revit", info)

ChangeSelection(uidoc)

End If

Catch e As Exception

message = e.Message

Return Autodesk.Revit.UI.Result.Failed

End Try

Return Autodesk.Revit.UI.Result.Succeeded

End Function

Private Sub ChangeSelection(uidoc As UIDocument)

' Get selected elements from current document.

Dim selectedIds As ICollection(Of ElementId) = uidoc.Selection.GetElementIds()

Dim opt As Options = New Options

Dim element As Element = Nothing

Dim solid As Solid = Nothing

Dim obj As GeometryObject

opt.DetailLevel = ViewDetailLevel.Coarse

TaskDialog.Show("Revit", "Number of selected elements: " + selectedIds.Count.ToString())

' Go through the selected items and filter out walls only.

Dim selectedWallIds As ICollection(Of ElementId) = New List(Of ElementId)()

For Each x As ElementId In selectedIds

element = uidoc.Document.GetElement(x)

If TypeOf element Is Wall Then

selectedWallIds.Add(x)

obj = element.Geometry(opt)

MessageBox.Show(obj.Id.ToString)

solid = TryCast(obj, Solid)

'HERE I'M RUNING INTO PROBLEM - CAN'T USE ACTUALY THE "solid" TO ComputeCentroid

'Dim centre As XYZ = solid.ComputeCentroid

'MsgBox(centre.X, centre.Y, centre.Z)

End If

End Sub

End Class

Re: Find Centroid of wall in Revit API

jeremy_tammik — Sat, 11 Feb 2023 08:22:53 GMT

So, once you have obtained the solid from the wall geometry, you will be able to call the ComputeCentroid method and all will be well.

In that case, a better title for this post would be "how to get a solid from a wall element".

I asked ChatGPT for you:

Jeremy: How can I obtain a solid geometry element from a Revit database element using the Revit API?

ChatGPT: To obtain a solid geometry element from a Revit database element using the Revit API, you can use the following steps:

Get the element's geometry element using the GeometryObject property of the element.
Check if the geometry object is a Solid using the IsSolid property of the GeometryObject class.
If the geometry object is a solid, cast it to a Solid object and use its properties and methods to manipulate the solid geometry.

Here is an example code snippet in C#:

// Assume "element" is the Revit database element you want to get the solid geometry from GeometryElement geometryElement = element.get_Geometry(new Options()); foreach (GeometryObject geomObj in geometryElement) { if (geomObj is Solid solid) { // Use the solid geometry // For example, you can get the volume of the solid: double volume = solid.Volume; } }

Note that not all elements in Revit have solid geometry, so you need to check if the geometry object is a solid before casting it to a Solid object.

This answer is correct, to the best of my knowledge. The official Revit SDK samples, The Building Coder and numerous other sources provide hundreds of samples illustrating the proper steps, so you should be able to manage on your own from here.

Actually, here is one of them that does exactly what you seek and more:

https://thebuildingcoder.typepad.com/blog/2012/12/solid-centroid-and-volume-calculation.html#6

Please note that generic questions such as this are more efficiently answered by searching the Internet yourself rather than waiting for me or other humans to address this thread and answer you by hand.

Good luck and have fun!

Re: Find Centroid of wall in Revit API

BBKENGJS — Sat, 11 Feb 2023 21:58:03 GMT

Thank You for the quick reply. However I'm still can not make it work.

Please help me to fix the cod.

Private Sub ChangeSelection(uidoc As UIDocument)

' Get selected elements from current document.

Dim selectedIds As ICollection(Of ElementId) = uidoc.Selection.GetElementIds()

Dim opt As Options = New Options

Dim element As Element = Nothing

Dim solid As Solid = Nothing

Dim obj As GeometryObject

opt.DetailLevel = ViewDetailLevel.Coarse

TaskDialog.Show("Revit", "Number of selected elements: " + selectedIds.Count.ToString())

' Go through the selected items and filter out walls only.

Dim selectedWallIds As ICollection(Of ElementId) = New List(Of ElementId)()

For Each x As ElementId In selectedIds

element = uidoc.Document.GetElement(x)

If TypeOf element Is Wall Then

selectedWallIds.Add(x)

obj = element.Geometry(opt)

MessageBox.Show(obj.Id.ToString)

If obj Is solid Then

solid = TryCast(obj, Solid)

End If

'HERE I'M GETTING ERROR IN REVIT:

' "Object reference not set to an instance of an object."

Dim centre As XYZ = solid.ComputeCentroid

MsgBox(centre.X, centre.Y, centre.Z)

End If

End Sub

Getting error in Revit : "Object reference not set to an instance of an object."

When I'm trying to use the "get_Geometry" Getting also error in M Visual Studio:

"get_Geometry is not a member of "Element" and I couldn’t find “get_Geometry” method in revitapidocs.

Private Sub Test()
Dim element As Autodesk.Revit.DB.Element = Nothing
Dim geometryElement As GeometryElement = element.get_Geometry(New Options())
Dim solid As Solid = Nothing

For Each geomObj As GeometryObject In geometryElement

If geomObj Is solid Then
solid = TryCast(geomObj, Solid)

Dim volume As Double = solid.Volume
End If
Next
End Sub

Re: Find Centroid of wall in Revit API

RPTHOMAS108 — Sun, 12 Feb 2023 02:23:18 GMT

Regarding your first error in red your 'solid' variable is not assigned anything because the first thing you will encounter from Element.Geometry will be a GeometryElement (collection object) containing solids not the solids themselves.

If obj Is solid Then solid = TryCast(obj, Solid) End If

That isn't how you do a type comparison, you got that right higher up in your code using 'TypeOf'. Here 'obj' is a GeometryElement and 'solid' is nothing. Although you know it isn't a solid at that point so you don't need to do that check.

Element.get_Geometry is only used in C# in VB.Net it is just Element.Geometry.

There is a basic example in RevitAPI.chm under Element.Geometry property:

Geometry Property (revitapidocs.com)

Re: Find Centroid of wall in Revit API

naveen.kumar.t — Sun, 12 Feb 2023 13:03:34 GMT

Hi @BBKENGJS ,

Have you tried exploring the element using the RevitLookup tool?

One suggestion is to explore the element using the RevitLookup tool. RevitLookup tool will help you to find out the value you need to set for your geometry option to get the required solid.

I think the problem lies in this line element.get_Geometry(New Options()).(Sometimes using "New Options()" won't work)

Instead of New Options(), please use app.Create.NewGeometryOptions().
Here is the sample code

Options options = app.Create.NewGeometryOptions(); options.ComputeReferences = true; options.IncludeNonVisibleObjects = true; options.View = doc.ActiveView; GeometryElement geometryElement = element.get_Geometry(options);

(Please set appropriate values to the geometry options properties, You can get this value from the RevitLookup tool)

Please take a look at the below link.
https://forums.autodesk.com/t5/revit-api-forum/identifying-the-light-source-geometry/td-p/9343436

Here is the link to download the RevitLookup tool.

https://github.com/jeremytammik/RevitLookup

Re: Find Centroid of wall in Revit API

jeremy_tammik — Sun, 12 Feb 2023 13:24:26 GMT

Dear Naveen and @BBKENGJS ,

ComputeReferences is only needed if you require references to the geometry, e.g., for dimensioning purposes. Furthermore, it adds computational effort. Therefore you should not set it to true unless needed:

Look at this recent benchmark result:

https://forums.autodesk.com/t5/revit-api-forum/computing-the-correlation-of-objects-in-revit/m-p/11701329/highlight/true#M68810

IncludeNonVisibleObjects is only required for certain supplementary graphical elements, e.g., for curtain walls:

https://thebuildingcoder.typepad.com/blog/2010/05/curtain-wall-geometry.html

I am pretty sure that it is never needed for such basic element geometry as solids.

So, I would leave both of those turned off in this case, set to their default value of false.

Furthermore, I very much doubt that there is any different between using `new Options` and `app.Create.NewGeometryOptions`.

However, specifying a view argument in the options will definitely make a difference, depending on the view you supply. That can be achieved using both `new Options` and `app.Create.NewGeometryOptions`.

I hope this clarifies.

Cheers

Jeremy

Re: Find Centroid of wall in Revit API

BBKENGJS — Sun, 12 Feb 2023 20:14:46 GMT

Thank you all for any suggestions. I managed to fix the cod. That was my first contact with Revit API, after my project required hundreds centroids for finding Lifting locations. It's a big shame that for the many we paid for Revit we can not get such basic things like e.g. centroid. So we have to spend another thousands to buy extensions or try to dig into Revit API. Now I have to add some extra cod which allow me to insert an instance of 3D family into centroid and add this point to assembly.

Here is my fixed cod:

Private Sub ChangeSelection(uidoc As UIDocument)

' Get selected elements from current document.

Dim selectedIds As ICollection(Of ElementId) = uidoc.Selection.GetElementIds()

Dim element As Element = Nothing

Dim solid As Solid = Nothing

TaskDialog.Show("Revit", "Number of selected elements: " + selectedIds.Count.ToString())

' Go through the selected items and filter out walls only.

Dim selectedWallIds As ICollection(Of ElementId) = New List(Of ElementId)()

For Each x As ElementId In selectedIds

element = uidoc.Document.GetElement(x)

If TypeOf element Is Wall Then

selectedWallIds.Add(x)

Dim wall As Wall = TryCast(uidoc.Document.GetElement(element.Id), Wall)

Dim wallGeo As GeometryElement = wall.Geometry(New Options())

For Each y As Solid In wallGeo

Dim centre As XYZ = y.ComputeCentroid

MessageBox.Show("CENTROID of WALL " & element.Id.ToString & vbCrLf & vbCrLf & " X= " & centre.X & " Y= " & centre.Y & " Z= " & centre.Z)

End If

' Set the created element set as current select element set.

uidoc.Selection.SetElementIds(selectedWallIds)

If 0 <> selectedWallIds.Count Then

TaskDialog.Show("Revit", selectedWallIds.Count.ToString() + " Walls are selected!")

Else

TaskDialog.Show("Revit", "No Walls have been selected!")

End If

End Sub

Re: Find Centroid of wall in Revit API

RPTHOMAS108 — Mon, 13 Feb 2023 01:35:24 GMT

That code can be simplified slightly

If TypeOf element Is Wall Then

Then

Dim wall As Wall = TryCast(uidoc.Document.GetElement(element.Id), Wall)

Still a wall (no need for TryCast depending on your options set).

Plus you have already got 'element' no sense in getting the same thing twice from Revit. The below would work fine with the default VB.net options:

Dim Wall as Wall = element 'or even Dim Wall = element

When iterating the GeometryObject items in the GeometryElement you should check each is a Solid rather than just assuming.

In general the geometry exposed by the API is a by-product of that used by Revit itself for graphical representation. Gravitational centroid is a bit problematic in general unless your wall is quite simple otherwise it could be affected by:

Differing densities of materials used in wall layers.

Wall sweeps/reveals defined on the types or hosted separately.