OpenSCAD User Manual/FAQ

From Wikibooks, open books for an open world
Jump to: navigation, search

General[edit]

How is OpenSCAD pronounced?[edit]

The intended pronounciation is: Open - ESS - CAD

Display[edit]

Preview doesn't appear to work at all[edit]

Force Goldfeather

Some systems, in particular Intel GPUs on Windows, tend to have old or broken OpenGL drivers. This affects preview rendering when using difference or intersection operators.

The following tends to improve the situation: Edit->Preferences->Advanced->Force Goldfeather (see screenshot).

What are those strange flickering artifacts in the preview?[edit]

OpenSCAD display issue with coincident faces

This is typically caused by differencing objects that share one or more faces, e.g.:

difference() {
  cube(20, center = true);
  cylinder(r = 10, h = 20, center = true);
}

In most cases the final render will be fine, but it's recommended to make the cuts a little bit larger to prevent this type of issues.

Note that this issue may also occur with faces that are not even visible in the final result, for example because they're removed by a difference() operation. This is an artifact of the library used for drawing the preview. See this discussion for an example and a workaround.

See also: https://en.wikipedia.org/wiki/Z-fighting


Why are some parts (e.g. holes) of the model not rendered correctly?[edit]

OpenSCAD display issue with convexity setting too low

This can happen when using features like linear_extrude() or when importing objects. The convexity of the objects is not known. For more complex objects, the convexity parameter can be used to specify the value. Note that higher values will cause a slowdown in preview.

difference() {
    linear_extrude(height = 15) {
        difference() {
            square([50, 50]);
            translate([10, 10]) circle(5);
        }
    }
    translate([25, 25]) cube([5, 5, 40], center = true);
}

See also https://en.wikipedia.org/wiki/Convexity_%28mathematics%29

Why is my model showing up with F5 but not F6?[edit]

OpenSCAD polyhedron with flipped face

This can be caused by polyhedrons with flipped faces.

This can be visualized in "Thrown Together" display mode. See misordered faces for details.

points = [[5,5,0],[5,-5,0],[-5,-5,0],[-5,5,0],[0,0,3]];
faces = [[0,1,4],[1,2,4],[2,3,4],[3,4,0],[1,0,3],[2,1,3]];
polyhedron(points, faces);

If the model imports external STL files, see also import related question.


Why is the preview so slow?[edit]

http://forum.openscad.org/Why-is-for-so-slow-tp11511p11531.html

This is hard to explain, but in essence, having intersections as the negative objects in difference is expensive. The preview rendering algorithm only allows having primitive objects as negatives, and everything else has to be unpacked.

For example (using A+B = union() / A-B = difference() / A*B = intersection()):

A - B*C - D*E

becomes: A-B-D + A-B-E + A-C-D + A-C-E

..and if A is more complex:

A+B - C*D - E*F

becomes: A-C-E + A-C-F + A-D-E + A-D-F + B-C-E + B-C-F + B-D-E + B-D-F

All combinations have to be rendered, which can take some time, especially on older GPUs, and especially on low-end Intel GPUs.

Import[edit]

Why is my imported STL file only showing up with F5 but not F6?[edit]

This is mostly caused by bad STL files, the best bet is to verify the STL file in a tool like Blender, MeshLab or NetFabb and fix the issues. In essence the model needs to be manifold to be processed in OpenSCAD.

The reason for the model still showing up in preview mode is that there is no real geometry calculation going on yet. The preview simply draws the triangles from the STL.

There is one specific issue that causes problems called "Zero faces" (meaning the STL contains triangles with zero area because all 3 points are on one line) which are currently not handled well in OpenSCAD.

Using MeshLab

MeshLab has a filter to remove zero faces by flipping edges of polygons

Filters -> Cleaning and Repairing -> Remove T-Vertices by Edge-Flip.

Set the Ratio to a very high value (e.g. 1000000), otherwise it's possible the model gets distorted.

Using Blender

Blender has a 3D-Printing-Toolbox Plug-in (needs to be enabled in the UserSettings) which can show issues with the STL file. See http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Modeling/PrintToolbox

Using NetFabb/Microsoft cloud service

The Microsoft 3D Model Repair service can help with fixing STL files. Make sure to read the service conditions before posting files. See https://modelrepair.azurewebsites.net/

I'm getting "Unsupported DXF Entity" warnings when importing DXF files, what does that mean?[edit]

DXF import sometimes produces warning messages like Unsupported DXF Entity 'SPLINE' (1c1) in "file.dxf". This means the DXF file is using features that the OpenSCAD importer does not know how to handle. The importer will simply ignore those unknown entities which could result in an incomplete model.

When using Inkscape, the easiest way to produces DXF files without unsupported entities is to convert all Bezier curves to short line segments using

Extensions -> Modify Path -> Flatten Beziers

The value given in the dialog will determine the length of the line segments. Lower values will produce smoother results, but also much more line segments. As export file format, use "Desktop Cutting Plotter (AutoCAD DXF R14)".

A more detailed tutorial is available at http://repraprip.blogspot.de/2011/05/inkscape-to-openscad-dxf-tutorial.html

Export[edit]

How can I export multiple parts from one script?[edit]

Answer based on comments in related issue on github https://github.com/openscad/openscad/pull/1534#issuecomment-227024209

There is a way to generate a bunch of geometric primitives and export them as STL files from a single script, without commenting/uncommenting code.

There is a variable, PARTNO, that indicates which part is being exported in the current run. If PARTNO is 'undef', then nothing is exported.

Image exported with PARTNO=0
 PARTNO = undef; // default part number
 
 module tree() {
   color("green") cylinder(r1 = 12, r2 = 1, h = 30);
   // ...
 }
 
 module trunk() {
   color("brown") cylinder(r = 3, h = 10);
   // ...
 }
 
 module base() {
   color("white") translate([-10, -10, 0]) cube([20, 20, 5]);
   // ...
 }
 
 if (PARTNO == 1) tree();
 if (PARTNO == 2) trunk();
 if (PARTNO == 3) base();
 
 // optionally use 0 for whole object
 if (PARTNO == 0) {
   base();
   translate([0, 0, 5]) trunk();
   translate([0, 0, 15]) tree();
 }

When working interactively, the PARTNO variable at the top of the file can be set to the number of the part that will be shown/exported from the GUI.

It's possible to automate the process of exporting all of the parts by writing a shell script on MacOS or Linux, or a batch file on Windows. The shell script would look something like this:

 # export parts as STL
 openscad -DPARTNO=1 -o tree.stl model.scad
 openscad -DPARTNO=2 -o trunk.stl model.scad
 openscad -DPARTNO=3 -o base.stl model.scad
 
 # export image of all the parts combined
 openscad -DPARTNO=0 -o model.png model.scad

Running this script once from the command line will export all of the parts to separate files.

Language[edit]

Why am I getting an error when writing a = a + 1?[edit]

http://forum.openscad.org/A-A-1-tp11385p11411.html

First of all, the question why we have these "limitations" will become more clear once we start better exploiting the opportunities.

  • We need a "reduce" function to help collecting information depending on a list of input. Recursion is fine, but people tend to struggle with it and we could offer some help.
  • We should probable disallow any attempt of reassignment, to make it more clear what's going on. The only real reason we partially allow it is to allow cmd-line variable overrides.

To help think about things:

  • Imagine every expression in OpenCAD being executed in parallel. Any dependency of existing expressions must be made explicit by hierarchical grouping. This will kill the idea of iterating in order to accumulate information.
  • In terms of functions: Imagine a function expression being something you'd type into a spreadsheet cell. Not totally mappable, but it might help framing it.

Now, we could add all kinds of sugar to help people apply their existing programming problem solving skills. Question is more if it really helps us, secondary who will spearhead the design of such language extensions, as we currently don't really have attachment for these ideas on the dev-team.

If you think about the OpenSCAD language as something similar to HTML, but for 3D modeling, you'd still have a need for various programs generating code in this language (similar to the plethora of HTML generators out there). There exist a number of tools for helping with OpenSCAD code generation from existing programming languages (python, ruby, C++, haskell, clojure off the top of my head) and there are tools offering Javascript interfaces for similar purposes (OpenJSCAD, CoffeeSCAD). Until we have a really good reason to do so in OpenSCAD proper, and a really good candidate for which language to support, I think it's better to keep these things separate.


see also for help: List Comprehension,Tips & Tricks

Recursive Functions

User Interface[edit]

I'm not getting any menubar when running OpenSCAD in Ubuntu, how can I get it back?[edit]

This seems to be caused by Ubuntu messing with Qt to move the menubar somewhere else (e.g. top of the screen).

That problem hits other applications too, see https://bugs.launchpad.net/ubuntu/+source/appmenu-qt5/+bug/1307619

There are two things that could help:

  • Set the QT_QPA_PLATFORMTHEME environment variable to an empty string (the default value is probably "appmenu-qt5") or simply run OpenSCAD with QT_QPA_PLATFORMTHEME= openscad
  • Remove the appmenu-qt5 package to globally disable menubar changes for all applications

Why are the error line numbers wrong?[edit]

That is a limitation/bug in the current parser that handles include<> basically as copy&paste of content. In some cases it's possible to work around the issue by placing the include<> statements at the end of the file.

When depending on libraries, it's recommended to use use<> instead which does not have that problem and also automatically inhibits any top-level geometry of that file (which might be there as demo for the library).

Errors / Problems[edit]

Why am I getting "no top level geometry to render"?[edit]

This can have different reasons, some common ones include

Missing / Commented out module call
module model() {
  cube(20);
}
%model();

Using the % modifier does not only make the part transparent, it's not included in the final render!

Difference / Intersection with wrong translated objects

The easiest way to solve this type of issues is to highlight the objects using the # modifier and see if the objects are placed at the position where they should be.

Importing broken STL files

See Why is my imported STL file only showing up with F5 but not F6?

OpenSCAD crashed/was killed, are my unsaved changes lost?[edit]

Before starting a preview or render process, the OpenSCAD editor writes a backup file in case there are unsaved changes.

This file is stored in the users documents folder in a separate directory (e.g. on Linux this is normally $HOME/.local/share/OpenSCAD/backups). The actual path can be checked in the Help->Library Info dialog where it is listed as "Backup Path".

Reporting bugs, Requesting features[edit]

How do I report bugs?[edit]

Bugs in OpenSCAD are best reported in the github issue tracking system at https://github.com/openscad/openscad/issues. If you are not sure it's a bug, asking on the mailing list/forum can help clarifying things.

Please try searching through the existing issues if the bug was already reported. If you find something similar or if you are unsure, create a new issue, but mention the (possibly) related one.

The bug report should give as much information as possible to help with reproducing it, including but not limited to

  • The OpenSCAD version
  • The Operating System name and version
  • A description of the scenario that produces the issue
  • In case of graphics issues, the OpenGL driver information
  • If possible, a trimmed down script reproducing the issue

Most of the technical version information can be found in menu Help -> Library Info.

How do I request new features?[edit]

New features or changes/extensions to existing features can be requested in the github issue tracking system at https://github.com/openscad/openscad/issues too.

Please make an effort to clearly explain the new feature / change as detailed as possible. Including some background about why you think this feature would be useful to you and other people helps a lot and increases the chances of it being implemented.

How do I report bugs that are related to the Operating System I use?[edit]

Windows[edit]

The Windows version is currently maintained by the OpenSCAD team, so please use the github issue tracker for reporting bugs.

Mac OSX[edit]

The Mac OSX version is currently maintained by the OpenSCAD team, so please use the github issue tracker for reporting bugs.

Linux[edit]

The OpenSCAD versions included in / distributed by the various Linux distributions are usually maintained by people/teams working with the distributions.

Specific bugs can be reported in the respective bug tracking systems, e.g.

The nightly builds hosted on the openSUSE build service are maintained by the OpenSCAD team, so please use the github issue tracker for reporting issues with those packages.