Bitmap Overlay - Quality What am I doing wrong?
Posted: 07 Apr 2014 18:54
Is this all you can achieve with Transdem? Or am I doing something wrong?
Ground textures in TransDEM and Trainz are constrained by two factors: pixel resolution and colour resolution. Both factors originate from the way Trainz implements ground vertices and their reference to textures. The total number of ground textures is limited to 250 per baseboard. Before TS2009 it was 250 ground textures per entire route. But even the greater freedom introduced with TS2009 does not allow us to create individual textures for each ground vertex. Instead, ground textures must be designed with reusability in mind. And the only reasonable solution is to use monochrome textures. This, in consequence, defines pixel resolution: 1 pixel per ground vertex, 5 or 10m. A 5m terrain grid is good for raster topo maps up to 1:25,000 or 1:24,000, while the 10m grid allows only 1:50,000 or 1:63,000. Any larger scale will come out blurred because then the map has a higher pixel resolution than the Trainz terrain. The result will be worsde for aerial images. A cartographic map is the result of an abstraction process: The information is condensed, map features like road, rail or water are being emphasized while "noise" (e.g. shade) is cut out. Furthermore, a typical cartographic map, the topographic map in particular, uses very few colours. This lead to an optimized ground texture set in TransDEM that has only 20 different textures which will reflect those maps quite naturally as Trainz terrain. However, any other sources, like aerial images or non-topo-maps with a large colour palette will come out rather poorly.
TransDEM offers an alternative approach here: The feature called UTM tiles. UTM tiles are large but otherwise ordinary Trainz objects, hovering slightly above or beneath the terrain surface, and acting as a texture carrier. The UTM tiles are either 500 x 500 m or 1000 x 1000 m. Since their 1000 m borders are always multiples of 1000m UTM geo coordinate grid lines, they have be named UTM tiles. Originally, UTM tiles were flat. They had to be adjusted to actual terrain elevation at the sport where currently used. However, with the latest TransDEM version 2.5, UTM tiles can now optionally be shaped by terrain elevation. Such tiles are called 3D UTM tiles. (3D tile generation is computation intensive and works best on a fast multi-core CPU.)
Some route builders prefer not to employ ground textures as a navigation/building aid but stick to UTM tiles alone. This makes ground textures free for other usage. One such usage could be automatic background texturing by aerial images. For this purpose, TransDEM 2.5 offers a new and additional texture set, which comprises 128 colours, optimised for ortho-photos. The individual textures are still monochrome, but unlike the standard textures they do not have the 10m grid, because their function is different. See here for an example: http://forum.transdem.de/viewtopic.php?f=2&t=295. See the TransDEM 2.5 announcement for 3D UTM tile examples.
