How to set material to the face of the Brep by api?

Scripting
,
1

In rhino we can set material to every face of the Brep easily,but how to do this by api?

1 Like
2
3

I want to set material not a color

4

Oops, sorry. I don’t know how to do that

5

Hi @duzhengjie1,

Just set BrepFace.MaterialChannelIndex with the rendering material channel index of your choice.

protected override Result RunCommand(RhinoDoc doc, RunMode mode)
{
  var rc = RhinoGet.GetOneObject("Select Brep", false, ObjectType.Brep, out var objref);
  if (rc != Result.Success || null == objref)
    return rc;

  if (!(objref.Object() is BrepObject brep_object))
    return Result.Failure;

  // Create red material
  var red_material = new Material { DiffuseColor = Color.Red };
  var red_material_index = doc.Materials.Add(red_material);

  // Create blue material with red material on one channel
  var blue_material = new Material { DiffuseColor = Color.Blue };
  var red_channel_index = blue_material.MaterialChannelIndexFromId(doc.Materials[red_material_index].Id, true);
  var blue_material_index = doc.Materials.Add(blue_material);

  // Change object material to blue material
  brep_object.Attributes.MaterialIndex = blue_material_index;
  brep_object.Attributes.MaterialSource = ObjectMaterialSource.MaterialFromObject;

  // Set every second face material to red material channel
  var brep = brep_object.BrepGeometry;
  for (var i = 0; i < brep.Faces.Count; i++)
  {
    if (i % 2 == 0)
      brep.Faces[i].MaterialChannelIndex = red_channel_index;
    else
      brep.Faces[i].ClearMaterialChannelIndex();
  }

  // Commit changes and redraw
  brep_object.CommitChanges();
  doc.Views.Redraw();

  return Result.Success;
}

– Dale

4 Likes
6

Ok,thanks very much!I have did it.

7

Hi @dale,
Is there a way to apply a rendermaterial from ActiveDoc.RenderMaterials to a brepFace using c# in Rhino8?

ObjRef objRef = gs.Object(i); // Get each selected object
RhinoObject rhinoObj = objRef.Object(); // Get the RhinoObject

// Apply the material or perform operations on the rhinoObj
if (applyToSubelement && objRef.GeometryComponentIndex.ComponentIndexType == ComponentIndexType.BrepFace)
{
    // Handle subelement (BrepFace) material application
    var brep = rhinoObj.Geometry as Brep;
    if (brep != null)
    {
        // Get the face index from the selected component
        int brepFaceIndex = objRef.GeometryComponentIndex.Index;
        BrepFace brepFace = brep.Faces[brepFaceIndex];
        

        // Apply the material to the BrepFace
        brepFace.MaterialChannelIndex = renderMaterial.ToMaterial(RenderTexture.TextureGeneration.Allow).Index;
        rhinoObj.Attributes.MaterialSource = ObjectMaterialSource.MaterialFromParent; // Use material from parent

        // Commit changes
        rhinoObj.CommitChanges();
        RhinoApp.WriteLine($"Material applied to BrepFace (index: {brepFaceIndex}).");
    }
}

This is what I am trying to do.

Thanks

8

Hi @svichare,

Does assigning per-face materials using indices acquired from the RhinoDoc.Materials table not work?

– Dale

9

Hi Dale,
Thanks for getting back.
I have made a new topic of what I am trying to achieve here.

In a nutshell, I am trying to apply a material to subelement using MateialChannelIndex as suggested by you and Jussi Aaltonen in other topics but it still unsuccessful.
I have provided an example of my code in the linked topic.

Cheers
Srujan

10

@svichare - does the sample code I posted above work for you?

– Dale

11

No it does not. I tried doing the sample code with blue/red material and use the redChannelIndex but it didnt work for me yet.

I am using Rhino 8

12

I just copied/pasted my sample code (above) into a Rhino 8 test command, and it work as expected.

image

– Dale

13

i will give it another shot and get back.

Thanks!

14

Hi @dale ,

The sample code works as shown in your image.
I am trying to implement a way where i can only paint one of the faces per click instead of doing a for loop to paint every other surface.

 // Apply the material or perform operations on the rhinoObj
 if (applyToSubelement && objRef.GeometryComponentIndex.ComponentIndexType == ComponentIndexType.BrepFace)
 {

     // Get the face index from the selected component
     int brepFaceIndex = objRef.GeometryComponentIndex.Index;

     // check if chosen renderMaterial exists in the doc.Materials table or else add the material
     var selectedDocMaterial = doc.Materials.FirstOrDefault(docMat => docMat.Id == selectedRenderMaterial.Id);

     // adding material to doc.Material table returns its index
     var selectedDocMaterialIndex = selectedDocMaterial == null ? doc.Materials.Add(selectedRenderMaterial.ToMaterial(RenderTexture.TextureGeneration.Allow)) : selectedDocMaterial.Index;

     var parentObjectMaterialDuplicate = rhinoObj.GetMaterial(true);
     var selectedMaterialChannelIndex = parentObjectMaterialDuplicate.MaterialChannelIndexFromId(doc.Materials[selectedDocMaterialIndex].Id, true);
     var modifiedParentObjectMaterialIndex = doc.Materials.Add(parentObjectMaterialDuplicate);


     // Apply the material to the BrepFace
     rhinoObj.Attributes.MaterialIndex = modifiedParentObjectMaterialIndex;
     rhinoObj.Attributes.MaterialSource = ObjectMaterialSource.MaterialFromObject; // Use material from parent

     // apply the material channel index to the brepface
     brep.Faces[brepFaceIndex].MaterialChannelIndex = selectedMaterialChannelIndex;


     // Commit changes
     rhinoObj.CommitChanges();
     RhinoApp.WriteLine($"Material applied to BrepFace (index: {brepFaceIndex}).");

 }

this works the first time i apply it to a new object of BrepObject type but it doesnt work when I use the command again to paint another face. It either applies the material to another face that I did not select or it does not apply any material to that face.
what can i do differently?

Thanks
Srujan