Can't get mesh vertex colors to render

I created a mesh with RhinoCommon, and it renders fine. Now I set its vertex colors with, for example,

mesh.VertexColors.CreateMonotoneMesh[System.Drawing.Color.Red]

But I can’t get the colors to show up in the Rhino viewport. Am I missing something obvious?

Try something like this.


`ImpMesh = Original Mesh ID

Dim Mesh As Geometry.Mesh = New DocObjects.ObjRef(ImpMesh).Mesh.Duplicate
Dim Red As Drawing.Color = Drawing.Color.FromArgb(255, 0, 0)
If Mesh.VertexColors.Tag.Id <> MyID Then
            Dim colors As System.Drawing.Color() = New System.Drawing.Color(Mesh.Vertices.Count - 1) {}
            For i As Integer = 0 To Mesh.Vertices.Count - 1
                    colors(i) = Red
              Next
     Mesh.VertexColors.SetColors(colors)
End If

doc.Objects.Replace(ImpMesh, Mesh)

Looks a bit messy when it’s pasted in here :stuck_out_tongue:

But probably you can do what you are doing now but you didnt Duplicate the original mesh and replaced it in the file :slight_smile:

Are you looking to add a mesh with vertex colours to the document or are you drawing it yourself using a Display Pipeline?

if this is Python, Vb.Net or C# code, these square brackets [] will not work. You need to call methods using parentheses (round brackets).

Jordy: Thanks for the example. So it’s not possible to update an existing mesh’s colors and tell it to redraw itself? I have to duplicate the mesh, change its colors, and then replace the original? Can you explain why that’s necessary, so I have the right model in my head of how Rhino works internally?

David: I want to modify the colors of a mesh that’s already in the document.

Piac: The source language is the Wolfram Language. I edited to make it look like C#, but missed the square brackets.

All geometry ‘inside’ the Rhino document is const. Nobody except us is allowed to change it. To open it up would basically allow any plugin developer to make changes that are both unexpected, untraceable and unstable. In order for Rhino to be reasonably stable while running a large number of plugins, and in order for undo to work well without placing a huge amount of responsibility on plugin developers, and in order to validate simplifying assumptions so the display can be optimized, all access to geometry inside the document is bottlenecked.

So yes, if you want to modify an object inside the document; get a copy of it, modify that copy, then replace the original with the modified object. The original object will be placed into the undo-buffer and a copy of your modified object will be inserted into the document.

That makes sense. Thanks for the explanation.