Implement DXF Importing

[dcowden]

Issue by dcowden
Sunday Dec 11, 2016 at 22:02 GMT
Originally opened as dcowden/cadquery#173

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Created from issue #155

[dcowden]

Comment by dcowden
Friday Nov 24, 2017 at 20:57 GMT

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Added a starting point. I have a whole zip file of all of the american steel shapes, and all of the 8020 shapes once we get this going!

[dcowden]

Comment by RustyVermeer
Tuesday Nov 28, 2017 at 18:21 GMT

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I have started poking around with the code in the DXF branch.

The following is a rough start at this only, of course.

import read_dxf as rd
from pointmap import *
import cadquery as cq
from cadquery import *

dwg = rd.import_drawing('tests/1515-ULS.dxf')

base = cq.Workplane('XY')

#add edges
for loop in dwg.get_loops()[0]:
    for e in loop:
        start = dwg.coordinates(e[0])
        startPoint = base.plane.toWorldCoords((start[0], start[1]))
        end = dwg.coordinates(e[1])
        endPoint = base.plane.toWorldCoords((end[0], end[1]))
        edgeData = dwg.edgeData(e)

        if edgeData == {}:
            line = Edge.makeLine(startPoint, endPoint)
            base._addPendingEdge(line)
        else:
            mid = edgeData['arc']
            midPoint = base.plane.toWorldCoords((mid[0], mid[1]))
            arc = Edge.makeThreePointArc(startPoint, midPoint, endPoint)
            base._addPendingEdge(arc)
    base.wire()

base.moveTo(0, 0).center(0, 0)

sorted_wires = sortWiresByBuildOrder(list(base.ctx.pendingWires), base.plane,[])
sorted_wires.reverse()

base2 = cq.Workplane('XY')

for wirelist in (sorted_wires):
    for wire in wirelist:
        print wire
        base2._addPendingWire(wire)

base2.consolidateWires()
base2.extrude(30.0).findSolid().exportStep('dxf_out.step')

What I've done in the above code is:

• read the dxf in using the import_drawing function
• set up an empty cq workplane
• for each loop, add either a line or arc according to the edgeData
• turn each loop into a wire
• create a new base workplane with reverse sorted list of wires. This is to (hopefully) guarantee that the largest loop is first in the list. I based this off of the fact that cq.Workplane('XY').circle(10).circle(20).extrude(10) results in 2 cylinders, but cq.Workplane('XY').circle(20).circle(10).extrude(10) results in a tube (what I think most users would expect)

I'm running into a problem with the 1515-ULS.dxf test file though.

That is the resulting step file opened in SolidWorks. It's missing the 2 end faces.

Without the center hole, things work as expected:

I am unsure how to solve this issue. Does FreeCAD or CQ have a notion of wire orientation?

Or perhaps I am just misusing available functions in CQ? Has this problem been addressed somehow in the extrude functions?

[dcowden]

Comment by dcowden
Tuesday Nov 28, 2017 at 22:29 GMT

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that's a great start. I think your approach is good. sortWiresByBuildOrder should return the outerwire first, but for extrusion i dont think it matters.

I think i see the problem. in the example, the inner contour doesnt look like its closed. The upper-right of the 'star' appears to be missing:

That could be an issue where the last contour is not being closed or whatever?

[dcowden]

Comment by RustyVermeer
Wednesday Nov 29, 2017 at 01:38 GMT

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Sort order does matter, actually. At least, it does for this particular case.

Leaving sort with outer wire later in the list produces (the 'default' output of that function):

Every loop was extruded as its own solid, so there are 5 separate solids in that image.

And reversing the sort (with the center 'star' thing filtered out just for this example):

As for your suggestion about a missing contour:
Unfortunately, that missing contour is just a graphical error. Here's the same part with a view exactly normal to that face:

There is no contour error there. I doubly confirmed that it's not open by extruding ONLY that star center, and it worked correctly:

Not sure how to tackle this particular issue. Any insights or ideas of where to look next?

Despite this, it's possible to make a workplane() function that imports DXF and creates wires on the stack, so I'll go forward with that, anyway.

[dcowden]

Comment by jmwright
Wednesday Nov 29, 2017 at 01:55 GMT

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This problem could be related to #83

I'm pretty sure that in some cases there's a glitch in how FreeCAD or OCC sort/order wires and edges. I've never had the time to dig into the FreeCAD internals to see where it comes from though.

[dcowden]

Comment by dcowden
Wednesday Nov 29, 2017 at 03:06 GMT

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Ah i see ok. Well, this is a really really great first try. I'm
disappointed to be running into a glitch, though i guess its a good thing
we started with a complex enough example to bring it to the surface.

I'm pretty sure it doesnt have anything to do with your code-- the solution
is probably inside or around the wire sorting code (sortWiresByBuildOrder).

It appears that when i wrote this, i may have even known this is an issue--
I can't remember writing this, but inside of sortWiresByBuildOrder, i say:

Assume:
The wires make up one or more faces, which could have 'holes'
Outer wires are listed ahead of inner wires
there are no wires inside wires inside wires
( IE, islands -- we can deal with that later on )
none of the wires are construction wires

FreeCAD should be smart enough to nest wires inside each other and figure
things out, but it clearly isnt. My hunch is that FreeCAD is expecting
the order of the edges to be in a particular order, and that it assumes the
normal direction based on that order. The theory would be that the order
of the edges in the 'star' wire are somehow backwards, causing FreeCAD to
think the material direction is in the wrong direction. My comments in
extudeLinear
https://github.com/dcowden/cadquery/blob/master/cadquery/freecad_impl/shapes.py#L846
imply
that I ran into this during development.

To test this theory, I would recommend reversing the order of the edges in
the 'star'. To do this, you can use Wire.assembleEdges() to control the
order of the edges by hand, and see if it magically fixes it. If it does,
that means that to get this to work, we'll have to do the work we expect
FreeCAD to be doing, and manually order the edges and the wires correctly.
That really stinks.

On Tue, Nov 28, 2017 at 8:55 PM, Jeremy Wright notifications@github.com
wrote:

This problem could be related to #83
dcowden/cadquery#83

I'm pretty sure that in some cases there's a glitch in how FreeCAD or OCC
sort/order wires and edges. I've never had the time to dig into the FreeCAD
internals to see where it comes from though.

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[dcowden]

Comment by easyw
Wednesday Nov 29, 2017 at 10:36 GMT

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Hi @dcowden @jmwright @RustyVermeer
in kicad StepUp to manage this I use the OpenSCAD2Dgeom function 'edgestofaces
face = OpenSCAD2Dgeom.edgestofaces(edges)
here a macro that uses this approach
https://www.freecadweb.org/wiki/Macro_DXF_to_Face_and_Sketch

[dcowden]

Comment by dcowden
Wednesday Nov 29, 2017 at 11:43 GMT

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@easyw thanks a bunch for this! That looks like just what we need.

[dcowden]

Comment by dcowden
Wednesday Nov 29, 2017 at 11:48 GMT

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...oh except I'd rather not import openscad code to solve it... Perhaps we can use the same approach but realized using the embedded occ code.

I think occ has a function that organizes edges as well

[dcowden]

Comment by easyw
Wednesday Nov 29, 2017 at 12:01 GMT

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@dcowden

I think occ has a function that organizes edges as well

please let me know which is in case you find it 😄

[dcowden]

Comment by dcowden
Wednesday Nov 29, 2017 at 12:19 GMT

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@easyw @RustyVermeer

ShapeAnalysisWire and ShapeAnalysisWireOrder are the ones I had in mind:

https://www.opencascade.com/doc/occt-7.0.0/refman/html/class_shape_analysis___wire.html
https://www.opencascade.com/doc/occt-7.0.0/refman/html/class_shape_analysis___wire_order.html

These would fix the problem if it is related to edge ordering. I am not sure they would fix the issue if they are related to wire nesting issues, however.

One other strategy might be to look at the FreeCAD code and see what they do when you extrude a drawing. I suspect that this case would work fine if the objects were imported into a sketch and then the sketch was extrude, so they solve it somehow....

[dcowden]

Comment by dcowden
Wednesday Nov 29, 2017 at 12:26 GMT

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Here is a starting point to get into what's going on in OCC land:

https://github.com/FreeCAD/FreeCAD/blob/master/src/Mod/Part/App/FeatureExtrusion.cpp

In this code you can begin to see the limitations of using OCC. Note on this line how FreeCAD folks have applied a work around to use a copy to work around a problem extruding circles:

https://github.com/FreeCAD/FreeCAD/blob/master/src/Mod/Part/App/FeatureExtrusion.cpp#L260

It looks like they have a dedicated class to make an extrudable face out of wires:

https://github.com/FreeCAD/FreeCAD/blob/master/src/Mod/Part/App/FeatureExtrusion.cpp#L304

https://github.com/FreeCAD/FreeCAD/blob/master/src/Mod/Part/App/FaceMaker.cpp