How to examine display resolution

Before examining the evidence, it is necessary to state a little bit about the methods, and in order to understand these a little bit more information about how Flight Simulator renders terrain is needed.

Terrain textures

Earlier we mentioned that the terrain in Flight Simulator is rendered (or drawn) in the simulator as a set of polygons, namely a pair of triangles for each set of four vertices in each rectangular area of terrain.

At this point some of you may well be wondering why you've never seen these polygons. Part of the reason is that the surfaces or the polygons are covered by textures which effectively hide the flat surfaces and the straight edges between them.

The textures used to cover the terrain polygons are provided either by the generic terrain textures supplied with Flight Simulator, or by photographic or satellite custom terrain textures added into the system in place of the generic terrain textures.

Generic and custom terrain textures are of a fixed resolution, i.e. ~4.8m, equivalent to LOD 13 or TMVL=23. Each 'pixel' of the terrain texture is ~4.8m by 4.8m, which may lead you to wonder why you can't see the straight edges between adjacent pixels.

There are two reasons for this:

1. Flight Simulator superimposes a more detailed texture to break down the original single terrain texture 'pixel' into 256x256 variations on the original texture colour, artificially adding ground texture.  This breaks up the edges of the original terrain texture pixel and adds a bit of artificial visual detail to the ground surface.
2. Bi-linear or Tri-linear filtering is softens the boundaries between adjacent terrain textures and terrain detail textures.

The result of all this is that it is actually very difficult to see the edges of the terrain polygons when viewing the terrain scenery as you normally would in Flight Simulator

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