topic Re: Merging all coplanar faces in Fusion API and Scripts Forum

Merging all coplanar faces

Anonymous — Mon, 15 Oct 2018 03:45:10 GMT

I've imported an STL and want to combine all coplanar faces to make working with the model easier. I can do this by switching of Capture Design History and using 'Merge' in the Patch workspace and chain selecting each face in turn.

Obviously this would be much nicer if it was automated but i cant find a mergeFeature in the API anywhere, is it there under a different name or is this achievable in some other way?

Re: Merging all coplanar faces

goyals — Mon, 15 Oct 2018 10:04:58 GMT

May be you can try stitch feature.

Re: Merging all coplanar faces

imajar — Mon, 27 May 2019 22:51:09 GMT

Same problem here: How to merge via API - Did you figure anything out? (stitch didnt merge any coplanar faces for me, unless I forgot to check a secret option?)

-Thanks

Re: Merging all coplanar faces

JesusFreke — Tue, 28 May 2019 00:57:39 GMT

Here's a quick function I whipped up that seems to work for me, on a simple cylinder that I exported and then reimported as a mesh, and then converted to brep. This may require the document to be in direct mode. I didn't try it in parametric mode.

import traceback
import adsk.core
import adsk.fusion


def run(context):
    try:
        root = adsk.core.Application.get().activeProduct.rootComponent  # type: adsk.fusion.Component
        merge_planar_faces(root.bRepBodies[0])
    except Exception:
        print(traceback.format_exc())


def collection_of(collection):
    object_collection = adsk.core.ObjectCollection.create()
    for obj in collection:
        object_collection.add(obj)
    return object_collection


def merge_planar_faces(body: adsk.fusion.BRepBody):
    first_temp_surface = None
    temp_unioned_surface = None

    brep = adsk.fusion.TemporaryBRepManager.get()

    for face in body.faces:
        # convert the face to a temporary BRepBody
        temp_surface = brep.copy(face)
        if first_temp_surface is None:
            # We need at least two faces to use a stitch feature, so keep a lone copy of the first face
            first_temp_surface = temp_surface
        elif temp_unioned_surface is None:
            # All the other faces get unioned into a single temporary BRepBody
            temp_unioned_surface = temp_surface
        else:
            # Adds this face to the temporary BRepBody that contains all the other faces
            brep.booleanOperation(temp_unioned_surface, temp_surface, adsk.fusion.BooleanTypes.UnionBooleanType)

    # Now stitch the first face, and all the remaining faces together, into a single solid body
    # This has the side effect of merging any coplanar faces that share an edge
    surfaces = [body.parentComponent.bRepBodies.add(first_temp_surface),
                body.parentComponent.bRepBodies.add(temp_unioned_surface)]
    stitch_input = body.parentComponent.features.stitchFeatures.createInput(
        collection_of(surfaces),
        adsk.core.ValueInput.createByReal(.01),
        adsk.fusion.FeatureOperations.NewBodyFeatureOperation)
    body.parentComponent.features.stitchFeatures.add(stitch_input)
    body.deleteMe()

Re: Merging all coplanar faces

imajar — Tue, 28 May 2019 16:31:48 GMT

Thank You! That was a great start. One question: I am having mixed results with this method. Sometimes it works and sometimes it does not!

I've attached a file with 2 bodies, one cleans up nicely, but the other does not. Somehow, the merge function is able to clean the second. Any thoughts about why stitch does not?

Thank You!

Re: Merging all coplanar faces

BrianEkins — Tue, 28 May 2019 19:08:34 GMT

I was curious about this and looked at your model. It seems the model where the faces are being merged aren't coplanar. If I change the preference setting so that angles are reported with more decimal places, I can see that they're not 180 deg and are likely outside the tolerance that Fusion considers coplanar.