Ruby framework for 2D mechanical sketches
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README.markdown

Sketching with Ruby

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Classes and methods for programmatically creating, manipulating, and exporting simple geometric drawings. This gem is primarily intended to support mechanical design generation, but it can also handle the doodling that you used to do in your notebook while stuck in that really boring class (you know the one).

At its most basic, Sketch is a container for Geometry objects. The classes in this gem are based on the classes provided by the Geometry gem, but have some extra magic applied to support transformations, constraints, etc. Like the Geometry module, Sketch assumes that primitives lie in 2D space, but doesn't enforce that constraint. Please let me know if you find cases that don't work in higher dimensions and I'll do my best to fix them.

License

Copyright 2012-2014 Brandon Fosdick bfoz@bfoz.net and released under the BSD license.

Examples

A basic sketch with a single circle

require 'sketch'

sketch = Sketch.new do
    circle center:[0,0], diameter:5	# Center = [0,0], Radius = 5
end

The same sketch again, but a little more square

Sketch.new { rectangle origin:[0,0], size:[1,1] }

You can also group elements for convenience

Sketch.new do
    group origin:[0,2] do
        circle center:[-2, 0], radius:1
        circle center:[2, 0], radius:1
    end
    circle center:[0, -1], radius:1
end

There's a shortcut for when you're only creating a group to translate some elements

Sketch.new do
    translate [0,2] do
        circle center:[-2, 0], radius:1
        circle center:[2, 0], radius:1
    end
    circle center:[0, -1], radius:1
end

Sometimes you feel like a group, sometimes you feel like a layout.

Sketch.new do
    layout :horizontal do
        circle center:[-2, 0], radius:1
        circle center:[2, 0], radius:1
    end
end

The layout command also takes options for spacing and alignment. For example, to add one unit of extra space between each element, and align them with the X-axis:

Sketch.new do
    layout :horizontal, spacing:1, align: :bottom do
        circle center:[-2, 0], radius:1
        circle center:[2, 0], radius:1
    end
end

Repetition

Do you ever get tired of making the same square over and over again?

Sketch.new do
    repeat count:2, step:[5,5] do
        square size:1
    end
end

Paths, Polylines and Polygons

If you're as old as I am, you might remember a certain turtle that would obey your every command. Well, any command involving a certain pen.

Sketch.new do
    polygon do      # Drawing a square, the hard way
        start_at    [0,0]
        up          5
        right       5
        down        5
        # Polygons close automatically; there's no need to draw the final line
    end
end

Simlarly, the path and polyline commands will create Path and Polyline objects, respectively. Neither paths nor polylines are closed by default, which allows you to draw any open shape you'd like. But, should you change your mind, just use the close command as the last line in the block to automatically close the shape.

Repeat

When you get tired of doing the same thing over and over, you can use the repeat command inside of the path, polygon, and polyline commands. It's not quite the same as the repeat command from the Sketch DSL, so be careful.

Sketch.new do	    # A simple panel with box joints on 2 edges
    polygon do
        start_at    [0,0]

        repeat to:[0, PANEL_HEIGHT], count:2 do |step|
            forward step/2
            right   PANEL_THICKNESS
            forward step/2
        end

        right       PANEL_WIDTH

        repeat to:[last.x, 0], count:2 do |step|
            forward step/2
            right   PANEL_THICKNESS
            forward step/2
        end
    end
end