256 lines
12 KiB
HTML
256 lines
12 KiB
HTML
<!doctype html> <html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<title>Create beautiful boards with Gerbolyze</title>
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<style type="text/css">
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@font-face {
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font-family: "playfair display webfont";
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font-weight: 600;
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src: url("fonts/playfair-display-v22-latin-ext_latin-600.woff2") format("woff2");
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font-family: "playfair display webfont";
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html, body {
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figure {
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</style>
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</head>
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<body lang="en">
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<div class="content">
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<h1>Create beautiful boards with Gerbolyze</h1>
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<p>
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Today, there is an increasingly large crowd of people who do artistic circuit board designs. People who fuse
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the roles of engineer and artist. Unitl today, circuit board design tools mostly ignore this use case and
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present a multitude of obstacles for such use. Gerbolyze finally solves this problem and presents an
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integrated solution for artistic PCB design that is compatible with real designer's workflows on one side
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and with real electronic design automation software on the other side.
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</p>
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<figure>
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<a href="pics/pcbway_sample_02_small.jpg"><img src="pics/pcbway_sample_02_small.jpg" alt="A printed
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circuit board showing a surrealist manga-style drawing of a woman sitting atop several traffic
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lights. The woman's hair looks golden from the circuit board's gold copper finish. The
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background is blue and white with scales of gray emulated through a halftone technique like it
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is used in newspapers."/></a>
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<figcaption>
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<strong>An artistic PCB design</strong>
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<p>
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This design was created from a digital artwork in a raster image file after circuit board
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manufacturer PCBWay offered me some free boards. The artwork was pre-processed using a raster
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graphics tool: It was split into layers for the different colors. Then, its color components were
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adjusted for brightness and contrast and finally passed through a raster-based halftone filter. The
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resulting file was then converted into circuit board manufacturing files using Gerbolyze.
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</p>
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</figcaption>
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</figure>
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<p>
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Thirty years ago, the world of printed circuit board design was revolutionized by the introduction of
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computer aided design tools. These tools enabled extremely complex designs through automation features
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like autorouting and through automatic design rule checking to weed out human error. While the first
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such tools were still very limited, their capabilites quickly grew and a few years after their
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introduction modern electronics design without computers was already unthinkable.
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</p>
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<p>
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Today, circuit board design programs can look back on a rich history and have accumulated a healty
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amount of expert knowledge in their design. Despite their difficult economic niche, even <em>free
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software</em> design tools have grown to become usable for advanced designs. However, all modern
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circuit board design tools are severely lacking in one area: That of <em>artistic</em> design. Many
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design assumptions are hard-wired deep into their design: Traces should be at 45° angles. Silkscreen is
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one opaque color. etc. These design assumptions lead to these tools being <em>in the way</em> more often
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than not for the increasing crowd of designers who try to create art with them.
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</p>
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<p>
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Gerbolyze solves this problem. Gerbolyze interfaces with circuit board design tools such as Altium or Kicad
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on one side through standard Gerber files. It interfaces with vector graphics editors such as inkscape on
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the other side through Scaleable Vector Graphics (SVG) files. By fusing both, it yields a powerful
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environment for artistic circuit board design.
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</p>
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<h2>Gerbolyze Algorithm Overview</h2>
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<p>
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Gerbolyze has two major components. The first is the gerbolyze executable itself, which orchestrates the
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process of fusing SVG and Gerber files. The second is svg-flatten, a tool encapsulating all of the
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heavy-duty computer graphics code. The gerbolyze executable is a python script for readability, while the
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geometry backend is a C++ binary for performance.
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</p>
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<p>
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In the beginning of the fusing process, the orchestrator figures out what semantic layers such as silkscreen
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or copper the tool's input files correspond to. The assigned layers are then processed one by one. For each
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layer, the tool first checks the input SVG file for any content. If there is none on this layer, the layer
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file is directly copied to the output. If ther is some, this SVG content is passed through the geometry
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backend to convert it to Gerber code. The resulting Gerber code is then read and added on top of the input
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file's gerber code. The result is written to the output.
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</p>
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<h2>The Computer Geometry of Scaleable Vector Graphics</h2>
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<p>
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The heavy lifting during this process is done by the geometry backend. While its job seems simple at first,
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it is surprisingly stretching the state of the art in both academic research and technical implementations
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of computer graphics. In its core the problem is that while SVG and Gerber are both essentially vector
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graphics formats, both have very different conceptions of their drawing models: They differ significantly in
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what happens when one of the input file's vectors is drawn.
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</p>
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<p>
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SVG is little more than a highly standardized description of the basic operations provided by the modern 2D
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graphics interfaces such as Qt, Cairo or Skia that are built-in to all operating systems. Drawing
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<em>paths</em> that are described by the vector coördinates of points along them is the most basic of these
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operations. SVG also includes support for a surprising number of decidedly <em>raster</em> operations such
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as masking but, operating on grayscales, these are less relevant for the type of design one would create
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when targeting circuit board production processes.
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</p>
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<p>
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Similar to SVG, the Gerber file format also targets a type of graphics programming interface. Only instead
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of that of operating systems 2D graphics APIs of the 90ies and 2000s, the Gerber format was created as a way
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to encapsulate commands for photoplotters, computer-controlled machines that physically move a light source
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across a photo-sensitive material. Gerber's concept of "aptertures" goes back to mechanical photoplotters
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having magazines of stencils of different shapes and sizes that could be swapped into the path of light
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during the plotting process.
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</p>
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<p>
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Like SVG has its paths, the Gerber format has polygons. Polygons were added to the format to ease the
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description of irregularly-shaped areas: Previously, these would have to be drawn by overlaying thousands of
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thin lines, described one by one in the Gerber file. Using a Polygon, one only needs to describe the shape's
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outline as a series of points and the photoplotter will fill in the rest.
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</p>
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<h2>Transforming Vectors into Vectors</h2>
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<p>
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The crux in converting from SVG to Gerber lies here, in the conversion of paths. While in both a path or
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polygon is described by its outline, which is described by points, there are significant differences in the
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limitations both place on these outlines. In SVG an outline can consist of several types of segments:
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besides basic straight lines, multiple types of parametrized curves including cubic bezier curves are
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possible. An SVG path's outline can self-intersect (cross over itself). The path can also have holes,
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additional parts that are inside the outline.
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</p>
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<p>
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Gerber, on the other hand, has a much more limited view of what a polygon is. In gerber, a polygon is
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something bounded by straight line segments, that cannot touch except under very particular circumstances,
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and holes are simply not supported. Converting from SVG's flexible model of a path to Gerber's very
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limited model of a polygon while preserving the fidelity of the input data is the true challenge here. As an
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aside, a fun complication one will encounter when embarking on this endeavour is that most programs that
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display Gerber files use modern graphics libraries in the backend. In these programs, a valid SVG path
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ineptly converted into an illegal gerber polygon may still end up looking alright since these programs
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usually just pass through the gerber's input data to the underlying graphics layer without validation—and
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that graphics layer is the one from SVG.
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</p>
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<h2>Styles and Strokes</h2>
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<p>
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</p>
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<!-- stroking -->
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<h2>Gerbolyze Image Vectorization</h2>
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<figure>
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<a href="pics/vec-comparison-poisson.png"><img src="pics/vec-comparison-poisson.png"/></a>
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<figcaption>
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<strong>Poisson-Disc Sampling</strong>
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<!-- ... -->
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</figcaption>
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</figure>
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</div>
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</body>
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</html>
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