A look at the detail of constructing the terrain: having built the stack of images,
I map out the landuse tiles by hand drawing the outlines, tracing over the map
or photo I use as reference - often switching out among several in the stack,
to get the best information - sometimes nothing is from the right period, and
I just have to guess. Near Dunkerque, the data is excellent. The TARA recon
images from 1944 overlap, and provide ample detail. Here is a chunk of the
and here are two tiles covering that area, detailed as well as seemed reasonable
to get away with:
But no, it turns out I used far more than my limit of 256 white dots (the landuse
is carved up by borders constructed of straight lines going from dot to dot, and
only 256 are permitted per tile. The tiles are compressed and encoded by just
storing the positions of the dots, and the direction of the lines between them.)
So, I have to strip out around 100 dots between these two tiles - I think it
was 65 on the left and 30 on the right - in order to get them to compile. I have to
try to remove the dots while losing a minimum of landscape information, to keep
the terrain as accurate and detailed as possible. The final result looks like this:
Both tiles have the maximum allowable dots, but still show far less detail than is evident
in the photos. Compromise is constantly required.
The landuse is now pretty much successfully generated, now it remains to tune up the
heightmap - fortunately this area is all at about 4m above sea level, but harbours are
always a problem. If you draw a dock, and set it at its true height, somewhere around
4m, it will be rendered hovering in the air, with no sides. The height is anchored at the
white dots, and the terrain mesh is built of triangle facets with the dots as vertices.
To have the dock sit at its true height, and also have a side going down to the water,
I'd have to draw two lines around the edge, one whose dots are set for the pier height,
and the other beside it set for the water height. But this would double the number of dots
required, which are already maxed, and the sides would not even be vertical. The rendering
engine does not like lines too close together -it would insist on two spaces between the lines.
But each space is about 5m horizontal distance, so the 4m height would be changed over
a 10m space, yielding a very shallow slope. So, it is impossible to do a good job with the
terrain engine. The solution is to make dock/pier objects, set the terrain to zero height at the
water's edge, and where possible set the terrain height to the correct value as close to the
pier as possible, hoping that the pier object doesn't have to be too huge to cover the space
from the water to the point where the terrain height can take over.
This area is also full of canals, whose edges present similar problems to the sides of the piers.
in some cases a line can be run along the side of the canal, if the shapes aren't too complex
(so the dot count stays legal), and these can often be roads, which are usually there anyway.
But there are just lots of places where it is impossible to find a perfect solution, so one has to
be resigned to the fact that it is only going to look good from a distance; and fortunately things
look best with lots of vertical distance, which is usually how they are viewed. Only I will zoom in
and see all the flaws...