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Author Topic: GUIDE - The Wonderful World of Addons Ending in "X"  (Read 2850 times)
Paul Wheeler
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« on: November 25, 2009, 12:41:29 PM »

Rough Guide to FSX Addons

GEX, UTX, FEX, FTX, REX, etc. etc. We've all heard of them, but do we all know exactly what they do?

There still seems to be much confusion in the FS world over exactly what each product with a TLA ending in X actually does so I have decided to write a quick guide which will hopefully help.

I have taken a small selection of addons to give a general example of what each type of addon offers. There are many other addons available but hopefully you will be able to compare them to a similar product in this list. For example, VFR London is very similar to Manhattan X.

This is not intended to comment on which addon is better but merely to give users a better idea of the differences between the various addons and which ones will work well together.

Scenery Addons

First we need to give definitions of a few important FSX terms.

Landclass - This is how FSX determines where to place a particular texture. The planet is divided up into a 1km by 1km grid and each 1km cell is given a landclass definition. This tells the sim which texture to draw within that cell. Each cell is then blended to the next using a "blend mask" which helps to avoid a "tiled" look.

Waterclass - Similar to landclass, except with water textures instead.

Mesh - Also known as Elevation Data, a mesh is used to describe the terrain height in the sim. It can be of various resolutions. LOD 9 (76m) is the general default resolution in FSX, although 3rd party meshes can get as accurate as LOD 12 (9m) and above.

Ground Textures - These are the textures that the sim shows in each cell. The landclass defines which texture is used in each cell.

Phototextures - This is an alternative method for drawing scenery instead of the landclass technique. An aerial photograph is drawn over a certain area. This has the advantage of being accurate to real life, however can suffer from many issues such as, lack of seasons, shadows, static cars on roads, shadows which don't move with the sun as they are drawn on the textures etc. Phototextures are always drawn on top regardless of their position in the scenery library.

Vector Roads - These are roads that are drawn in the sim using vectors. They have the advantage in that they can be drawn 100% accurate to real life, however as they are drawn on top of the landclass textures they will cut across these textures, often going straight through, for example, buildings etc.

Vector Streams/Railroads/Utility lines - Other vector features similar to roads (or is that toads Tongue)

Autogen - This is what the sim uses to display generic 3D objects such as houses and trees. The position of autogen is determined by the underlying ground textures. Some packages actually include their own autogen models.

Scenery Objects - These are hand-placed models usually used to depict important landmarks. These are independant of the ground textures and always take priority over autogen.

Important Notes

  • UTX has only partial waterclass. It does not feature waterclass for its entire coverage area.
  • UTX only has partial groundtextures. It adds a few custom landclass definitions such as cemeteries, universities, etc. and it installs the ground textures associated with these custom landclasses.
  • UTX has the ability to change the "tint" of water. It does this by manipulating the waterclass and does NOT change any actual water textures.
  • FTX features completely custom landclass, ground textures, autogen, etc. and also features major changes to certain FSX system files. Thus, it can cause issues with other addons and requires the use of a "mode switch" to fly outside coverage areas.
  • This refers to the FTX AU packages and not the specific airport or city sceneries.
  • GEX entirely replaces the default ground textures for its coverage area and thus, is 100% compatible with other addons. It also features replacement models for the default autogen.

Environment Addons


Weather Engine - This downloads real world weather data and uses it to render weather effects in the sim. It tends to be far more accurate and complex than the built-in weather engine.

Water Textures - These are textures that are used to create water in the sim. There are several classes of these textures and they often feature a "burnt in" static wave pattern.

Wave Animations (Water Normals) - These are a set of textures that are used to create the moving "wave" effect on the water. They are separate to wave effects that are "burnt in" to the underlying water textures.

Shaders - These are used to render "special effects" such as reflections on water and wave animations (not the animation texture itself).

Airport Environment - This usually refers to specific airport textures such as runway textures, taxiway textures, parking textures, etc.

Final Thoughts

So, as you can see there is a great deal of differences between all the different addons. As a rule, as long as the addons don't feature a "yes" in the same column then you should be able to run them both together quite happily without their features overlapping. Of course if they are scenery addons that have different coverage areas they should be OK. Most of these addons do feature the ability to switch off certain features enabling the user to customise which addon does what.

This very simplified guide is, as it says, just a guide. As for which addon is better... well that's for you to decide!  Thumbs Up
« Last Edit: November 27, 2009, 04:35:58 PM by Paul Wheeler » Logged

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