TriangleMesh.FromModel

public static TriangleMesh FromModel(Model model)
{
  var triangleMesh = new TriangleMesh();

  foreach (var modelMesh in model.Meshes)
  {
    // Get bone transformation.
    Matrix transform = GetAbsoluteTransform(modelMesh.ParentBone);

    foreach (var modelMeshPart in modelMesh.MeshParts)
    {
      // Get vertex element info.
      var vertexDeclaration = modelMeshPart.VertexBuffer.VertexDeclaration;
      var vertexElements = vertexDeclaration.GetVertexElements();

      // Get the vertex positions.
      var positionElement = vertexElements.First(e => e.VertexElementUsage == VertexElementUsage.Position);
      if (positionElement.VertexElementFormat != VertexElementFormat.Vector3)
        throw new NotSupportedException("For vertex positions only VertexElementFormat.Vector3 is supported.");
      var positions = new Vector3[modelMeshPart.NumVertices];
      modelMeshPart.VertexBuffer.GetData(
        modelMeshPart.VertexOffset * vertexDeclaration.VertexStride + positionElement.Offset,
        positions,
        0,
        modelMeshPart.NumVertices,
        vertexDeclaration.VertexStride);

      // Apply bone transformation.
      for (int i = 0; i < positions.Length; i++)
        positions[i] = Vector3.Transform(positions[i], transform);

      // Get indices.
      var indexElementSize = (modelMeshPart.IndexBuffer.IndexElementSize == IndexElementSize.SixteenBits) ? 2 : 4;
      if (indexElementSize != 2)
        throw new NotSupportedException("Only 16 bit indices are supported.");

      var indices = new short[modelMeshPart.PrimitiveCount * 3];
      modelMeshPart.IndexBuffer.GetData(
        modelMeshPart.StartIndex * 2,
        indices,
        0,
        modelMeshPart.PrimitiveCount * 3);

      // Remember the number of vertices already in the mesh.
      int vertexCount = triangleMesh.Vertices.Count;

      // Add the vertices of the current modelMeshPart.
      foreach (var p in positions)
        triangleMesh.Vertices.Add((Vector3F)p);

      // Add indices to triangle mesh.
      for (int i = 0; i < modelMeshPart.PrimitiveCount; i++)
      {
        // The three indices of the next triangle.
        // We add 'vertexCount' because the triangleMesh already contains other mesh parts.
        var i0 = indices[i * 3 + 0] + vertexCount;
        var i1 = indices[i * 3 + 1] + vertexCount;
        var i2 = indices[i * 3 + 2] + vertexCount;

        triangleMesh.Indices.Add(i0);
        triangleMesh.Indices.Add(i2);     // DigitalRune Geometry uses other winding order!
        triangleMesh.Indices.Add(i1);
      }
    }
  }

  return triangleMesh;
}


private static Matrix GetAbsoluteTransform(ModelBone bone)
{
  if (bone == null)
    return Matrix.Identity;
  return bone.Transform * GetAbsoluteTransform(bone.Parent);
}