Scale: A Question in Two Parts

[Zarylin]

Hello all,

So in my quest to improve my map-making abilities (which here means drawing and using my own brushes), I've been running into the same problem over and over, which basically boils down to scale.

My first question is how much room (in pixels) do you normally give yourself to work with for a region? A continent? An entire world? What are some common scales (pixels to image sizes, and pixels to miles)? I know that second part can vary wildly, but any sort of starting point would be helpful information.

My second question involves making brushes and other pre-drawn icons. Should I start much larger and then scale down on the actual map? Draw a 300x300 tree, then shrink it to 20px wide when I draw? Or should stamps be drawn in approximately the same scale as the intended project? How well do things scale up and down? I use Gimp, and my experience tells me that scaling things around does not work very well, but again, other people's experiences and tips would be a big help.

Thanks in advance!

[Midgardsormr]

To your first question: I usually set my canvas size to my desired final output size. Lately, I have been displaying my maps on an HDTV, and I have not needed the ability to pan around on them, so I have been designing at 1920 x 1080, the native resolution of my television. When I designed a poster map, I knew my final output was going to be 32" x 24", and I wanted 200 dpi, so I started at 6400 x 4800. (Desired physical size multiplied by desired print resolution will yield pixel dimensions.) The type of map doesn't really matter to me at this point. I can make a poster-sized continent map or a page-sized battlemat, or vice versa.

Scale is a somewhat more involved discussion. If you're making a battlemat for D&D, or another game that uses similar rules, the convention is that each 1 inch square represents a 5-foot square. If you want to print the battlemat at 150 dpi, then 5 feet = 1 inch = 150 pixels. If you never intend to print, then you can drop any reference to dpi and inches, and just say 5 feet = 150 pixels. Or 100 pixels, or whatever you think will work best for you.

Sometimes scale is dictated by other limitations, such as the time I was working on modeling the Nazca plateau in Peru. I had a height map with a resolution of 3 meters per pixel, and that was the smallest I could go without having to generate artificial detail. I eventually abandoned that project, although I hope to return to it at some point.

And sometimes scale is relatively arbitrary: divide your map's logical width (300 miles) by the image's width (1200 pixels) to get its scale (.25 miles per pixel).

Now, the second question is fairly straightforward. My advice is to make your brushes roughly 2 - 4 times larger than you intend to use them. Never scale up if you can help it, because that will cause softening. Theoretically, you can make the icon or brush as large as you please, but it's easier to design closer to your usage size so that you have some idea of what kinds of details will be visible when you actually use the brush. And, the smaller you go, the more you risk filtering doing something unexpected. Check out Redrobes' article on bitmapped images for some details on that. His illustration with the zebra is particularly relevant.

[Zarylin]

Thanks, that's fairly helpful. I suppose as a follow up question though, I'd have to ask what the advantage is to different levels of dpi, and more info on that topic. I've seen general statements like 300dpi if you plan on printing, but only 150dpi for online use... I honestly don't even know exactly what the acronym dpi stands for, beyond the obvious context clues.

Also, I did a quick search for the article you mentioned, but I wasn't able to locate it.

[Midgardsormr]

DPI stands for "dots per inch," and it refers to the density of the ink when you print. 300 dpi printed on quality paper will look pristine to the eye when held at typical reading distance. 600 dpi is about what you get from a professionally printed photograph, and fine art prints might go as high as 1200. A wall poster is frequently somewhere around 150 - 200, since it's meant to be viewed from a few feet away. If you set your word processor to print in draft mode, you'll probably get 100. High quality mode will likely be either 200 or 300. Note that the quality of the paper is also an important variable. If you try to print 300 to ordinary copy paper you'll saturate it, and the colors might bleed.

If you start talking about images that will only be viewed on the screen, then dpi is meaningless, as there is no way of knowing what the actual dimensions of the viewer's screen are, nor the density of pixels on that screen. The only thing that matters for online images is actual pixel dimensions. You will hear people insist that images designed for the screen are 72 dpi, but that's a holdover from the earliest Macintosh computers, which were designed in such a way as to make each pixel the same physical size as a point in print production (72 points = 1 inch). The truth is that if the image is only electronic, then dpi can be set to anything, and it won't change how the image looks.

The thread I mentioned is here: http://www.cartographersguild.com/tu...explained.html

[Zarylin]

Oh wow, that's awesome. Gonna need some time to work through and digest all the information in there, but that looks like it should answer a lot of the more technical questions I've had popping around in my head.

The explanation/history on dpi is also a big help, thanks a bunch!