Get objects on a specific layer

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Permalink Reply by David Rutten on August 30, 2010 at 4:15pm

Private Sub RunScript(ByVal layer As String, ByRef A As Object)
   Dim layer_index As Int32 = doc.Layers.Find(layer, True)
   If (layer_index < 0) Then Return

   Dim lay As Rhino.DocObjects.Layer = doc.Layers(layer_index)
   Dim objs As Rhino.DocObjects.RhinoObject() = doc.Objects.FindByLayer(lay)
   If (objs Is Nothing) Then Return

   Dim geo As New List(Of GeometryBase)
   For Each obj As Rhino.DocObjects.RhinoObject In objs
     geo.Add(obj.Geometry)
   Next

   A = geo
End Sub

Try this. A single String input for this script.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Marc Syp on August 31, 2010 at 11:53am

Thanks David, that works great.

One more thing... how would I also retrieve the layer color assigned to the layer (not the material but the display color)?

Thanks.

Marc

Permalink Reply by David Rutten on August 31, 2010 at 2:54pm

Layer has a Color property, so:

Dim layerColor As Color = lay.Color

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Marc Syp on August 31, 2010 at 3:04pm

Wow, that was embarrassingly simple. Thanks.

Permalink Reply by Marc Syp on September 1, 2010 at 7:21am

So, after some experimentation I see that the drawback of using this method is that the GH definition is not automatically updated when the gathered geometry is changed. I'm guessing that this is because of the way that Grasshopper is driven directly by referenced geometry as opposed to geometry that is gathered by the execution of a script.

Obviously the workaround is to set up a timer to continually check the geometry on the layers (executing the script on a regular basis), but then you get lag in the viewport, even with large timer intervals.

Are there any other solutions I'm missing? I'd like to have the definition rebuild every time one of the objects changes, but I don't want to force the user to reference the geometry manually in GH.

Thanks,
Marc

Permalink Reply by David Rutten on September 1, 2010 at 7:57am

That is not the obvious workaround. The best solution in fact is not a workaround at all.

Instead of populating the Script node output with pure geometry, you should create actual Grasshopper Geometry data that knows it is linked to an actual object.

You can use the Kernel.GH_Convert.ToGeometricGoo() or Kernel.GH_Convert.ObjRefToGeometry() methods to convert a Rhino object ID into the appropriate Grasshopper Geometry Data instance.

This should ensure that changes to the original objects also cause updates in Grasshopper. What it won't do is update the definition if more objects are added to the layer. For this you should have event handlers that listen to layer and document changes.

Using timers is a terrible idea, almost always. Sometimes they are the only way to solve something, but you should definitely deplete any alternatives first.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Marc Syp on September 8, 2010 at 8:51am

The workaround is only obvious because I had no clue how to do it properly. Anyway, if I knew how to use those methods I would definitely try it. :) (See next discussion topic.)

Permalink Reply by Marc Syp on September 27, 2010 at 8:02am

Event handlers listening to the layer to document changes, that sounds perfect. Is this just a couple lines of code? My first thought would be to use a handler to detect that a change has been made, and in such a case force GH to recalculate the solution. Or perhaps that is not as simple as it sounds?

Marc

Permalink Reply by Marc Syp on September 27, 2010 at 8:17am

btw,

When I try to use the methods you mention above, I get errors that "Convert is not a member of Kernel", and when I try to use Kernel.GH_Convert.ObjRefToGeometry() (somthing I found after some exploration), I get "Value of type 'Rhino.DocObjects.RhinoObject' cannot be converted to 'Rhino.DocObjects.ObjRef". Am I using the wrong method? I can't find just a simple Kernel.Convert in the script editor.

Thanks,
Marc

Permalink Reply by David Rutten on September 27, 2010 at 9:41am

Marc,

sorry, you're right, it's supposed to be GH_Convert. I updated my original answer.

As for the second problem; RhinoObject is a different beast from ObjRef. You cannot supply a RhinoObject when an ObjRef is asked for. Luckily you can construct ObjRef from a RhinoObject:

Dim ref1 As New DocObjects.ObjRef(rhobj)
Dim ref2 As New DocObjects.ObjRef(rhobj.Id)

where rhobj is an instance of RhinoObject.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Marc Syp on September 27, 2010 at 9:56am

Okay, thanks for staying with me here... so far I've got the code in and I'm not getting any errors, but I'm not getting any updates when manipulating the Rhino geometry either...

Here is my code:


Dim layer_index As Int32 = doc.Layers.Find(layer, True)

If (layer_index < 0) Then Return

Dim lay As Rhino.DocObjects.Layer = doc.Layers(layer_index)
Dim objs As Rhino.DocObjects.RhinoObject() = doc.Objects.FindByLayer(lay)


If (objs Is Nothing) Then Return

Dim layerColor As Color = lay.Color
Dim geo As New List(Of GeometryBase)
For Each obj As Rhino.DocObjects.RhinoObject In objs
Dim ref1 As New DocObjects.ObjRef(obj)
Dim ref2 As New DocObjects.ObjRef(obj.Id)
Kernel.GH_Convert.ObjRefToGeometry(ref1)
geo.Add(ref1.Geometry)


Next

L = geo
col = layerColor

I'm thinking that the problem might be either in the way i'm using the convert method (probably wrong) or in the "geo.Add(ref1.Geometry)" line... Anyway, any help appreciated.

Thanks,
Marc

Permalink Reply by David Rutten on September 27, 2010 at 12:21pm

Hi Marc,

ObjRefToGeometry() takes an ObjRef and it returns an instance of some Grasshopper data type (which one depends on the kind of geometry) that references that geometry. I might also return a null if it cannot find any Grasshopper data type that matches the rhino object type, such as PointClouds, Dimensions or DetailViewports.

You're not storing the result of ObjRefToGeometry so calling this function isn't accomplishing anything at the moment.

You need to do this:

Dim goo as IGH_GeometricGoo = GH_Convert.ObjRefToGeometry(ref1)
geo.Add(goo)

of course this does mean you need to change geo from

Dim geo As New List(Of GeometryBase)

to

Dim geo As New List(Of IGH_Goo)

--
David Rutten
david@mcneel.com
Poprad, Slovakia

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