Workshop: Introduction to 2D CAD (with Inkscape)

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(Generally, this workshop is offered at least once every two weeks on a rotating basis. Check the Lab calendar for up-to-date availability!)

This tutorial will cover the basics of 2-dimensional Computer-aided design (CAD) using the software Inkscape.

Vectors

You may have used a digital drawing program before - perhaps MSPaint, or Paint.net, for example. Many drawing programs, including the two previously mentioned, store the image you create in bitmap form: it is made of an array of pixels, and each pixel is assigned a certain color. There is another way, however, to store image information: in the form of vectors. A vector is nothing more than at least two points in 2D space, in between which a line is drawn. In actuality, vectors stored as equations for a line, defined by the xy values of each of the points.

Why does this matter? Unlike a bitmap - which can be recreated in the real world with something like a dot-matrix printer - a vector drawing can be interpreted by a fabrication device which has xy controls and which understands equations. These devices make it possible to fabricate much more intricate designs than devices which work with bitmaps.

There are many vector-drawing applications; each effectively has the same capabilities, just organized differently. In DaBL we use Inkscape, because it is cross platform as well as free.

Vector components:

  • Nodes (for anchor points)
  • Node handles (for creating Bezier curves)

Object properties

Object and path properties:

  • Stroke
  • Fill

The Inkscape UI

Inkscape UI is fairly straightforward:

  • Tools panel on left
  • Drawing canvas in middle
  • Snapping panel on right
  • Floating windows which can be docked (including Stroke and Fill, Layers, et al.)

Layers

Layering is a way of organizing the objects on the canvas. It operates in a vertical hierarchical manner, the top most layer will correspond to the top layer of the image and so on. This is useful for perspective because you can make individual layers visible and invisible, as well as for grouping.


Make sure, as with all digital design packages, to save early and save often. You will want to make sure to save as type .SVG (Scalable Vector Graphics)

Tracing an Image

Inkscape has a useful tool for converting colored, shaded, or other images into vector images that Inkscape draws in. The tracer that Inkscape provides does not fully copy your image into your drawing; It does however, give you options to choose curves and the definition of a picture for you to use in your drawing.

In general, the darker your image, the harder it will be to trace.


(see example)

1: To begin tracing an image, first select it

2: Select the Path > Trace Bitmap item, or Shift+Alt+B.

3: I) Select live preview to view your image

II)Choose your settings in the pop-up window

III) Press ok

4: Your traced Image should on your document

5: Inkscape recommends simplifying your lines. Simplify your nodes with Path>Simplify

<gallery mode="traditional">

File: Bit1.png | Select your Image

File: Bit2.png | Select bitmap

File: Bit3.png | Choose mode and thresholds

File: Bit4.PNG | Lines

File: Bit5.PNG | Simplify your lines

</gallery>


Preparing your designs for CAM

If you're eventually going to be using one of DaBL's machines to fabricate your design, some considerations are in order. Each machine's CAM software has a specific way of interpreting your design; as such, setting up your design in a certain way may work for one type of machine, but not another. Each of the following CAM packages will allow import of 2D vector files:

Workshop checklist

By the end of this Workshop, you should:

  1. Understand what vectors are.
  2. Know how to resize the canvas and change the default measurement units.
  3. Be able to move elements around the canvas..
  4. Know how to work with vectors, including how to split and merge them.
  5. Know how to work with layers.
  6. Be able to snap elements to other elements.
  7. Understand and utilize stroke and fill to change the appearance of elements.
  8. Know how to change the default color system and manipulate the palette.
  9. Be able to save your design as a PNG and as a PDF.