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How X-Plane Builds the World

X-Plane ships with a scenery that looks plausible from altitude, but it is far from photorealistic. With the right add-ons, however, the visual quality can be transformed dramatically. To get there, it helps to understand the three layers that make up X-Plane's scenery system: the terrain Mesh defines elevation, Orthos provide satellite imagery as ground textures, and Autogen populates the landscape with 3D objects.

Meshes

The mesh is the terrain's elevation model — a network of triangles (a Triangulated Irregular Network, or TIN) that defines heights and slopes. Each triangle vertex carries a coordinate with longitude, latitude, and elevation. Together, these triangles shape mountains, valleys, and plains.

Mesh data is stored in X-Plane's DSF (Distribution Scenery Format) files. The default mesh ships with the simulator; higher-resolution alternatives (e.g., HD Mesh Scenery) can be installed as scenery packs.

The mesh provides structure only — no textures or objects.

Orthos

Orthos (orthophotos) are aerial or satellite images projected onto the mesh as ground textures. They replace X-Plane's procedural land classes with photorealistic imagery — roads, fields, forests, and buildings become visible from altitude.

X-Plane uses DDS (DirectDraw Surface) textures internally. Source images from map providers (JPEG, PNG) are converted to GPU-compressed DDS format (DXT1/BC1 or DXT5/BC3) before X-Plane can use them.

Tools like Ortho4XP generate these DDS tiles offline, while streaming solutions deliver them on demand (see below).

Autogen

Autogen (automatically generated scenery) adds 3D objects — buildings, trees, vehicles, power lines — to the landscape. X-Plane reads placement information from its DSF scenery files and distributes objects accordingly: trees in forest areas, buildings in residential zones, factories in industrial areas.

The placement data in X-Plane's default scenery is derived from OpenStreetMap and other geographic datasets during Laminar Research's scenery build pipeline. This data is baked into the DSF files — X-Plane does not query OSM at runtime. Third-party add-ons like SimHeaven X-World use OSM data separately to generate more detailed autogen coverage.

How the Layers Interact

The three layers build on each other in a fixed order:

  1. Mesh — defines elevation and terrain shape
  2. Ortho — projects satellite imagery onto the mesh surface
  3. Autogen — places 3D objects based on land use data

Each layer depends on the one below it. Orthos need the mesh to be projected correctly, and autogen needs both mesh and ortho data to place objects at the right positions and elevations.

Add-ons

Several add-ons extend the default scenery layers:

  • Ortho4XP — generates high-resolution ortho tiles offline from satellite imagery
  • Ortho Streaming — AutoOrtho, XEarthLayer, and XPME stream satellite imagery on demand, no pre-generation needed
  • Custom Sceneries — higher-resolution meshes or regional autogen objects (e.g., SimHeaven X-World)
  • Autogen Libraries — additional object sets for more varied building and vegetation placement

The scenery_packs.ini Load Order

The landscapes in X-Plane are created through the interaction of various components: meshes, orthos, autogen, and special sceneries like airports. X-Plane processes scenery_packs.ini from top to bottom — entries listed higher have higher priority and override entries below them. Getting this order wrong can cause floating airports, invisible scenery, or autogen objects covering runways.

Layer priority (bottom → top of the file)

Priority Layer Function Example
6 (top) Custom Sceneries & Landmarks Detailed airports, landmarks Aerosoft_EDDF_Frankfurt_3_Scenery
5 Global Airports Default airports (X-Plane Gateway) *GLOBAL_AIRPORTS*
4 Special Objects Radio masts, wind turbines world_wind_turbines
3 Autogen & Libraries 3D objects (buildings, trees, vehicles) simHeaven_X-World_Europe-6-scenery
2 Ortho Sceneries Satellite imagery on the mesh z_ortho_California
1 (bottom) Mesh Files 3D terrain structure (elevations, valleys) HD_Mesh_Scenery

Global Airports position

The line SCENERY_PACK *GLOBAL_AIRPORTS* must sit below custom sceneries but above autogen, orthos, and meshes. If placed too low, autogen objects can cover runways and taxiways; if placed too high, custom airports lose their override. An incorrect position often causes "floating" airports or missing details.

Example of a Correct Order

Here is an excerpt from a typical scenery_packs.ini (from top to bottom, i.e., in the order X-Plane loads them):

# Custom Airports and Landmarks (highest priority)
SCENERY_PACK Custom Scenery/Aerosoft-EGLL Airport London-Heathrow_1_DefaultStreets/
SCENERY_PACK Custom Scenery/Aerosoft-EGLL Airport London-Heathrow_2/
SCENERY_PACK Custom Scenery/Aerosoft_EDDF_Frankfurt_1_Parked_Cars/
SCENERY_PACK Custom Scenery/Aerosoft_EDDF_Frankfurt_2_Roads/
SCENERY_PACK Custom Scenery/Aerosoft_EDDF_Frankfurt_3_Scenery/
SCENERY_PACK Custom Scenery/X-Plane Landmarks - Berlin and Frankfurt/
SCENERY_PACK Custom Scenery/X-Plane Landmarks - London/
SCENERY_PACK Custom Scenery/X-Plane Landmarks - Paris/

# Global Airports (standard airports)
SCENERY_PACK *GLOBAL_AIRPORTS*

# Special Objects and Masts
SCENERY_PACK Custom Scenery/Usa_Radio_Masts_01/
SCENERY_PACK Custom Scenery/Usa_TV_Masts_0/
SCENERY_PACK Custom Scenery/world_wind_turbines/

# SimHeaven X-World (Autogen)
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-1-vfr/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-2-regions/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-3-details/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-4-extras/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-5-footprints/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-6-scenery/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-7-forests/
SCENERY_PACK Custom Scenery/simHeaven_X-World_Europe-8-network/

# Ortho Sceneries
SCENERY_PACK Custom Scenery/z_ortho_California/
SCENERY_PACK Custom Scenery/z_ortho_Colorado/
SCENERY_PACK Custom Scenery/z_ortho_Florida/
SCENERY_PACK Custom Scenery/zz_Ortho_Alps_West/
SCENERY_PACK Custom Scenery/zz_Ortho_SpainUHDv2_1/

# Mesh Files (lowest priority)
SCENERY_PACK Custom Scenery/FlyTampa_Athens_3_mesh/
SCENERY_PACK Custom Scenery/FlyTampa_Amsterdam_4_mesh/
SCENERY_PACK Custom Scenery/KDEN-Denver International Airport_Mesh/
SCENERY_PACK Custom Scenery/SFD_EDDM_Munich_2_Mesh/

Maintaining scenery_packs.ini

  • Use tools — programs like XOrganizer can automatically optimize the order and detect conflicts.
  • Create a backup before editing scenery_packs.ini to be able to undo mistakes.
  • Test after changes — load a scenery in X-Plane and check airports, orthos, and autogen. Pay special attention to "floating" objects or missing details.
  • Watch for updates — new sceneries or add-ons can disrupt the order. Check the file regularly, especially after installations.

Further Reading

Topic Page Focus
Scenery Sources Scenery Standard scenery, SimHeaven, freeware, and payware options
Orthophotography Concepts & Methods Static vs. streaming approaches for ortho textures
AutoOrtho AutoOrtho Real-time ortho streaming via FUSE
XOrganizer XOrganizer Scenery management and load order optimization
Filesystem Filesystem I/O tuning for scenery loading performance
GPU & VRAM GPU & VRAM VRAM considerations for scenery layers

Sources