By Alex Richards
At the end of the last article I introduced the subject of tracing. This is without doubt the most powerful technique a budding cartographer can develop, allowing you to move beyond reliance on existing outline maps created by others and allowing you to convert any existing map you might find to something you can use for your own purposes. It's also invariably the most time-consuming part of any map, a fact which probably explains why so many avoid it.
Be aware, some parts below get quite technical, but I'll be happy to answer any specific questions arising in the discussion thread associated with this article.
What to trace?
Naturally nobody wants to embark on a lengthy and time-consuming project without reason, so the logical question is what you actually need to trace from an existing source map. To a great extent this depends on how detailed an end result is desired, itself largely determined by how large a map you're making- larger maps can accommodate more detail without feeling cluttered, but also require more detail to avoid looking flat and empty. Style also plays its part- maps from the 18th Century tend to have a much denser quantity of features (towns, rivers and so forth) than the sort of modern political maps you might be familiar with from school atlases.
Natural features are the best to trace as not only do these define the shapes of many countries- either through coastlines or international boundaries- but are also the most familiar to most people and so the most obviously 'wrong' if depicted incorrectly. Borders are more likely to be changed in any alternate history map, but here too tracing can provide the guideline, either through tracing existing boundaries (national or subnational) or through using natural features on the sourcemap as an indication on where to create a boundary. Meanwhile rivers are one of the most common examples of something that can either enhance or detract from a map- it can be best to do a full treatment of the area of the map most dense with other features (such as around the capital of a nation, or where several small nations are close together) in order to work out whether or not to include a given feature.
Across all programmes, the use of layers makes tracing significantly easier. I will usually start with the coastline, then have separate layers for national borders, subnational borders, lakes and rivers and other features as Appropriate. Positioning the coastline layer- with the major bodies of water filled in- as the topmost of these means that untidiness in lower layers can be hidden- such as tracing a small section of border and then filling in a peninsular by just creating a box around the area rather than having to trace the coastline twice or having to smarten up the join between national border and coastline.
Tracing in Raster Programmes
While theoretically MSPaint can be used to trace boundaries, since this requires drawing in the desired lines, and then using the paintbrush or eraser tools to remove the background image from around them, it is not a very practical option. More useful here is Paint.NET and its use of layers, and here there are three tools which will be most useful in tracing. The pencil tool produces a single-pixel wide line, and is thus the most commonly used option when creating editable basemaps from an existing source map. The paintbrush tool can be used to create thicker lines and by default has a softer 'blur' effect allowing for more artistic techniques. Both of these are used as you'd expect- you pick a starting point and just drag the mouse along the border or coastline. The line tool can also be used if desired, either for accurately drawing straight line boundaries without risk of deviating, or by using the nodes that appear along its length to create curves approximately following the desired path. As a general rule, the more accurate or detailed you want a given line to be, the more you should be looking at either the pencil tool or the brush tool with a small 'head' setting.
For Raster programmes the chief difficulty is managing the conflicting issues of ease of adding colour against the desire for a 'soft' border effect rather than the more pixelated look. This can be controlled using the antialiasing option available with most tools and, in Paint.NET, located in the tool bar at the top of the screen. With antialiasing on, you end up with a more blurred soft effect that helps avoid the classic 'made on computer' look. However this is then harder the fill in without creating jpeg artefact effects around the edges. Disabling antialiasing creates hard, blocky borders but these create easy to fill in shapes. Using a second layer for colour to the border layer can help here, which I'll discuss further in a future article.
Paint.NET also features a potential shortcut in the form of the 'outline' tool found under the effects tab. This can be used to quickly convert a simple source image- such as an existing province map. However the more complex the source map, the less useful this tool becomes.
Tracing in Vector Programmes
Vector programmes remove the chief difficulty of Raster programmes- whatever shape is created can be coloured in through use of the fill menu without creating any artefacts, and on export to bitmap a 'soft' effect is naturally produced. It's also possible to create very accurate boundaries or coastlines which will retain their accuracy at any scale. However, doing this creates a path with many nodes, and the more nodes you have, the larger the file size and the more likely it is that further manipulation will create issues.
Inkscape has two tools which can be used for tracing. The 'freehand lines' tool is essentially the equivalent of the paintbrush/pencil tool, though as this is a vector programme whatever line you draw will be defined as a series of connected nodes indicating points where change of direction occurs. The 'Bezier curves' tool on the other hand can be used to draw straight or, by click-and-dragging, curved lines. One important thing to remember is that as all these lines are defined by nodes, your initial tracing can be a bit looser and rougher, as any deviations from the desired path can be corrected by dragging nodes to their proper place. It's also worth remembering that the more zoomed out you are while tracing, the fewer nodes that will be created as you're tracing, with slight wiggles tending to be elided by the programme where they would be kept on a smaller field of view. Whether this is desirable or not is a question you'll need to answer yourself.
コメント