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

Scripting
,
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