Centroid and AreaMassProperties class

Replies to This Discussion

Permalink Reply by Steve Baer on May 25, 2011 at 2:01pm

Instances of the AreaMassProperties are created by calling the Compute function on the AreaMassProperties class. Your code should be changed to look something like..

 


Private Sub RunScript(ByVal ArrSrf As List(Of Surface), ByRef A As Object)
  Dim ArrCent As New List(Of Point3d)
For j as Integer = 0 To ArrSrf.count() - 1
Dim massProps As AreaMassProperties = AreaMassProperties.Compute(ArrSrf(j))
Dim CentPt As Point3d = massProps.Centroid
ArrCent.Add(CentPt)
Next
A = ArrCent
End Sub

Permalink Reply by Minh on May 26, 2011 at 3:47pm

it works, thanks

 

But I don't get why you need to compute instead of doing like I did?

 

cheers

Permalink Reply by Steve Baer on May 26, 2011 at 4:47pm

because there is no AreaMassProperties function on a Surface instance

-Steve

Permalink Reply by Minh on May 30, 2011 at 1:48am

http://www.grasshopper3d.com/forum/topics/geometry-array-and-sorting

 

Well, I should have precise a bit more my question. I don't understand the writing evolution from this topic  

http://www.grasshopper3d.com/forum/topics/geometry-array-and-sorting

to the new SDK. 

Even if the entities are Brep they is no more AreaMassProperties function, right?

 

Sorry, for stupid question but I try to understand.

 

Permalink Reply by David Rutten on May 30, 2011 at 6:01am

Hi Min,

 

There needs to be a function somewhere that computes the area/mass properties of a piece of geometry. The most obvious options are:

 

1. On the piece of geometry itself
2. On the class that maintains the area/mass data
3. As a static (Shared) method on a utility class

 

The first option was picked for the old SDK. It makes intuitive sense to put it on the geometry itself, but the downside is that we'll have these methods sprinkled all over the SDK (one on surface, one on brep, one on mesh, one on extrusion objects etc. etc.)

 

For RhinoCommon we chose to put this function on the AreaMassProperties class. The benefits of this choice are that all the functions to do with area/mass computation are in a single spot, so they're easier to find. It's also easier to provide overloads for computing multiple shapes at the same time, as this function can take a collection of breps all in one go. Another benefit is that classes like Surface, Brep and Mesh remain somewhat simpler.

 

Personally I prefer the second option, but I'll grant you that's little more than an opinion.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia