What magic does baking do to make Breps more realer?

Grasshopper
1

I am doing this work in a C# script node;

I tried to CreateBooleanUnion on a list of Breps. It failed.

I tracked down the problem to just one Brep. (deck1)

I unioned the rest into a Brep called: union. This gives me a valid, solid, closed Brep with no bad edges (open , not manifold).

Things go horribly wrong when this line is executed:
Brep saucer = Brep.CreateBooleanUnion(new Brep[]{union, deck1}, 0.01)[0];

  1. error: Object reference not set to an instance of an object. (line: 176)

0.01 is RhinoDocument.ModelAbsoluteTolerance;

The strange thing is…

if I do this: A = new Brep[]{union, deck1};

and I bake A…

and do this…

image_2022-09-14_182806564

where the two baked breps are put into the Brep node (Set Multiple Breps)

and the code in the script node is: A = Brep.CreateBooleanUnion(x, 0.01)[0];

then it works and A contains a valid, closed Brep.

Things break again if I connect A directly to x.

image
image1208Ă—774 93.4 KB

So it looks like the process of baking does something to make the two Breps more better than they were when un-baked.

What on earth is baking doing? If I knew then maybe I could do that too.

I have tried:

    foreach(Brep b in x)
    {
      b.Compact();
      if (BrepSolidOrientation.Inward == b.SolidOrientation)
      {
        b.Flip();
      }
    }

    A = Brep.CreateBooleanUnion(x, 0.01)[0];

but to no avail.

It just seems that baking a Brep makes it better somehow.

2

I should have said: this is in the latest Rhino 7 on Windows but I have seen this in previous versions of Rhino.

I have a workaround where I

  1. split the script into 2 scripts
  2. bake the output of the first
  3. put that into a Brep node and internalize it
  4. Put that Brep into the second node

Obviously that sucks but it works(ish).

3

I feel dirty but there might be a hack to get the magic baking goodness…

I could try:

  • adding the Breps to the document - note their Guids
  • load them back into my script
  • perform the union on the loaded Breps
  • remove the temporary Breps from the document

I’m going to try that when I get home tonight.
Has anyone had experience of this? Any tips?

I will let you know how I get on…

4

what does
deck1.GetType();
return ?
check also:
deck1.IsValidTopology();
IsValidTopology

Grasshopper does a lot of casting and conversion between the output and input of the components. This might explain the described “baking behaviour”.

5

GetType says that both are Rhino.Geometry.Breps and IsValidTopology is true

The temporary bake hack works!!! :slight_smile: I am so happy :slight_smile:

So…

  • If you have boolean or fillet ops that fail in code
  • if you expected them to work
  • and they work when you bake the objects
  • then try something like the temporary bake hack below
Guid unionGuid = RhinoDocument.Objects.AddBrep(union);
Guid deck1Guid = RhinoDocument.Objects.AddBrep(deck1);
union = (Brep) RhinoDocument.Objects.FindGeometry(unionGuid);
deck1 = (Brep) RhinoDocument.Objects.FindGeometry(deck1Guid);

Brep saucer = Brep.CreateBooleanUnion(new Brep[]{union, deck1}, t)[0];

RhinoDocument.Objects.Delete(unionGuid, true);
RhinoDocument.Objects.Delete(deck1Guid, true);

I hesitate to mark this as an answer because I still don’t understand why baking helps.

6

it s a unexpected workarround, not a solution.

Can you somehow reproduce the error in a simplified version and post both the .3dm and .gh file so others can reproduce what you’re seeing ?
if there is a bug in the background, would be sad if it s not tracked.

Where does the geometry of deck1 comes from ?
Are you doing some geometry modification of “deck1” ? before you run the boolean operation ?

@dale
does AddBrep() perform some cleaning / updating of the geometry ?

7

I’m going to try to make an example 3dm and grasshopper file to illustrate.

I use custom C# components to build geometry and many other C# script nodes so I don’t know yet if I have to include the built components and a large chunk of everything else.

But I will know once I try…

Well, I have tried and it looked like I had a minimal example that showed failure. I deleted some “unused” layers and saved the files.

I then opened them and I can’t get it to fail.

I tried opening the grasshopper file in the big 3dm with all the layers. Didn’t fail.

Tried running Rhino in the debugger but to no avail.

Still fails if I use the big 3dm and the big grasshopper file but that would need the built component assemblies as well.

8

Hi @Tom_P,

When you add a Brep to the document, two things happen:

1.) If kink splitting is enabled (which it is unless it is being overridden temporarily by a plug-in), then BrepFaceList.SplitKinkyFaces() is called, which splits any faces with creases into G1 pieces.

2.) If the Brep’s solid orientation is inward, then it is flipped using Brep.Flip().

– Dale

2 Likes
9

This fixes things without a bake.


      union.Faces.SplitKinkyFaces(RhinoDocument.ModelAngleToleranceRadians);
      deck1.Faces.SplitKinkyFaces(RhinoDocument.ModelAngleToleranceRadians);
      saucer = Brep.CreateBooleanUnion(new Brep[]{union, deck1}, t)[0];

How do I know if a face is kinky? I would like to bake them and have a look at the offending faces.

10

I brute forced it.

      List<Brep> theKinkyOnes = new List <Brep>();
      foreach(BrepFace face in union.Faces)
      {
        Brep b = face.DuplicateFace(false);
        int initialCount = b.Faces.Count;
        b.Faces.SplitKinkyFaces(RhinoDocument.ModelAngleToleranceRadians);
        if (b.Faces.Count > initialCount)
        {
          //theKinkyOnes.Add(face.DuplicateFace(false));
          foreach(var v in b.Faces)
          {
            theKinkyOnes.Add(v.DuplicateFace(false));
          }
        }
      }
      A = theKinkyOnes;

got this

image
image2132Ă—1314 161 KB

I know where that is and can find where I make it and fix it at source (make it better or split it immediately after making)

Thanks Dale. I will mark your post as the answer.