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union()
{
translate([0, 0, 6])
scale([0.9842519685, 0.9842519685, 1])
import("floor.stl");
cube([50, 50, 6]);
}

Original problem using OpenSCAD to import an STL fils

union()
{
  translate([0, 0, 6])
  scale([0.9842519685, 0.9842519685, 1])
  import("floor.stl");
  cube([50, 50, 6]);
}

Error message Rendering Polygon Mesh using CGAL... ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion violation! Expr: e_below != SHalfedge_handle() File: /usr/include/CGAL/Nef_3/SNC_FM_decorator.h Line: 426

Fix the problem using AngelCADs polyfix utility:

$ polyfix floor.stl 

Parameters:
  input_file = floor.stl


polyhedron 0 ================= volume=10890.5, dtol=0.01, atol=1e-06, maxiter=10
iteration 0: vertices=92100 faces=30700
         warning: 1 zero area faces.
         warning: nonmanifold edges: uc(1)=92100 
         merged 76748 vertices
         removed 1 collapsed or zero area face
         split 1 face
         total changes=76750
         no warnings

iteration 1: vertices=15352 faces=30700
         total changes=0
         no warnings

Summary: 
         polyhedron 0: vertices=15352 faces=30700 : no warnings

Writing: floor_1.stl

... polyfix finished, time used: 0d 00h 00m 01s

Then import the repaired file into OpenSCAD and press F6

union()
{
  translate([0, 0, 6])
  scale([0.9842519685, 0.9842519685, 1])
  import("floor_1.stl");
  cube([50, 50, 6]);
}

The problem is now gone

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@Kevigsp

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Kevigsp commented May 13, 2020

I installed Angelcad and vcredist_X64 for the mscv dll
Angelcad starts but if i enter the above code:
$ polyfix floor.stl

       Parameters:
            input_file = floor.stl

i get an error:
as_csg started.
asERR : (line 1, col 1) : Unexpected token '' : asFILE=C:/Users/Henk/Documents/floor.as
asERR : Please correct the errors in the script and try again.
asINFO: (line 0 , col 0 ) : Script execution failed.

what am i doing wrong?

windows 10, x64
the floor.stl file in:
documents
documents\xcsg
c:\programfiles\angelcad
C:
and tried with the path in the name (c:\floor.stl)

henk

@arnholm

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arnholm commented May 13, 2020

Polyfix and Angelcad are 2 different executables (polyfix is installed alongside AngelCAD though). You must run polyfix from the command line, outside AngelCAD.

This gist is about running polyfix to fix a bad STL. The .scad scripts shown here are for OpenSCAD.

The error you describe is from "as_csg" which is AngelCADs language interpreter. If you want to import the file into AngelCAD you must first use polyfix to convert/fix the original STL into .off or .obj format

polyfix floor.stl -out=floor.off
Parameters:
    input_file = floor.stl
    out = floor.off

Then you can import it in AngelCAD

floor_angelcad.as

// AngelCAD code.
shape@ main_shape()
{
   return polyhedron("floor.off");
}

void main()
{
   shape@ obj = main_shape();
   obj.write_xcsg(GetInputFullPath(),secant_tolerance:-1.0);
}

For general support questions relating to anything AngelCAD, consider using the AngelCAD forum at https://forum.abmesh.com/

@Kevigsp

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Kevigsp commented May 13, 2020

thanks,
just tried running from command prompt and it works like a charm!
where can i find (if there are any) other parameters for polyfix?

rgrds
Henk

@arnholm

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arnholm commented May 13, 2020

Just type on command line (without any parameters)

polyfix

then you get

Usage: polyfix [-verbose] [-maxiter <str>] [-dtol <str>] [-atol <str>] [-lumps] [-nflip] [-remesh <str>] [-overwrite] [-out <str>] [-zip]  <input_filename>
  -verbose              Verbose messages
  -maxiter=<str>        [heal]          Max iterations (def=10)
  -dtol=<str>           [heal]          Distance tolerance (def=1.0E-2)
  -atol=<str>           [heal]          Area tolerance (def=1.0E-6)
  -lumps                [heal]          Split into lumps (not supported for stl output)
  -nflip                [heal]          Flip faces with inward normals (experimental)
  -remesh=<str>         [remesh]        Heal & remesh surfaces to given edge length (set dtol to small value ~1.E-6)
  -overwrite            [output]        allow file overwrite, including input file.
  -out=<str>            [output]        output filename/format (.obj, .off, .amf, .stl, .astl)
  -zip                  [output]        save output also to compressed zip file
@Kevigsp

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Kevigsp commented May 13, 2020

thank again,
this is very helpfull an solved a lot of troubles for me

rgrds
Henk

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arnholm commented May 13, 2020

You are welcome, please tell your friends/colleagues about the software so it becomes better known.

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