occult

vpype plug-in to remove lines occulted by polygons from SVG files.

Examples

Basic usage

Draw a line, then a square:

vpype line 0 0 5cm 5cm rect 2cm 2cm 1cm 1cm show

Same drawing, after applying occult:

vpype line 0 0 5cm 5cm rect 2cm 2cm 1cm 1cm occult show

Order of path is important: occult will consider the last geometry in a SVG file to be "on top" of all other geometries, the last but one is above every other geometries except the last one. For instance, using vpype rect 2cm 2cm 1cm 1cm occult show will not modify geometries.

Working with multiple layers

By default, occult performs occlusion layer by layer. For instance, applying occlusion on the image below will not change anything:

occult -i ignores layers, so that occlusion is performed on all objects, regardless of their layer. Geometries in layers with a larger ID number are considered to be "on top" of geometries in layers with a smaller ID number.

• Without -i flag

• With -i flag

Save occulted lines

occult -k keeps occulted lines in a separate layers.

• Without -k flag

• With -k flag

Using vpype's viewer (show command), you can visualize occulted lines and remaining lines separately.

Using occult with Vsketch

occult can be invoked from a Vksetch sketch, using vsk.vpype("occult"). When using the GUI, calling occult within the sketch draw() method will display occulted geometries at each code save / seed change. For sketches with lots of geometries, occlusion can take a significant amount of time. Invoke occult within the finalize() method of a sketch to perform occlusion only when saving a specific output.

import vsketch

class Sketch(vsketch.SketchClass):
    def draw(self, vsk: vsketch.Vsketch):
        vsk.size('10x10cm')
        vsk.scale('mm')
        
        vsk.line(-5, -5, 5, 5)
        vsk.circle(0, 0, 3)

        # Uncomment to perform occlusion at every GUI reload
        # vsk.vpype("occult")
  
    def finalize(self, vsk: vsketch.Vsketch) -> None:
        # Occlusion (and other vpype commands) invoked only when saving
        vsk.vpype("linesimplify occult linemerge linesort")


if __name__ == "__main__":
    Sketch.display()

Installation

See the installation instructions for information on how to install vpype.

Existing vpype installation

Use this method if you have an existing vpype installation (typically in an existing virtual environment) and you want to make this plug-in available. You must activate your virtual environment beforehand.

$ pip install git+https://github.com/LoicGoulefert/occult.git#egg=occult

Check that your install is successful:

$ vpype --help
Usage: vpype [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

Options:
  -v, --verbose
  -I, --include PATH  Load commands from a command file.
  --help              Show this message and exit.

Commands:
[...]
  Plugins:
    occult
[...]

Stand-alone installation

Use this method if you need to edit this project. First, clone the project:

$ git clone https://github.com/LoicGoulefert/occult.git
$ cd occult

Create a virtual environment:

$ python3 -m venv venv
$ source venv/bin/activate
$ pip install --upgrade pip

Install occult and its dependencies (including vpype):

$ pip install -e .

Check that your install is successful:

$ vpype --help
Usage: vpype [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

Options:
  -v, --verbose
  -I, --include PATH  Load commands from a command file.
  --help              Show this message and exit.

Commands:
[...]
  Plugins:
    occult
[...]

Documentation

The complete plug-in documentation is available directly in the CLI help:

$ vpype occult --help

License

See the LICENSE file for details.