A word about overlays and meshes

One of the most annoying parts of using X-Plane with Ortho scenery is the overlay data sourced from a rough approximation of real life.

Probably half the comments I get about the scenery is to do with the Overlay objects, such as roads, trees, buildings and power lines etc. Neither, I nor Ortho4XP really generate the overlay. It simply extracts the data from another source and processes it into the scenery package. I use the default data in X-Plane, which is okay, but also noticeably wrong in many areas. For example, you’ll see trees placed on the wharf where cargo is managed, or you’ll see a road that goes up the mountain, while the ortho shows it zig-zagging with switchbacks. A big issue is that X-Plane likes to randomly place viaduct roadways elevated above the ground, which looks totally overblown in cost in remote places like the Chatham Islands.

The data is never going to be perfect, in fact X-Plane can’t handle the amount of data it would take to keep the coordinates of each road or tree. In order to draw the roads, they use a rough approximation – taking a couple of known points and drawing a curve between them that is kinda close to how the real road goes. This means that the overlay objects are often out of place.

Ortho4XP on the other hand downloads OpenStreetMaps data with pretty precise locations of each road, and as it is building the terrain mesh, it will ensure that the places the roads cover are flattened to play nicely with the objects.

However when you combine the approximate overlay road, with the mesh that is using flattening for the real location of the road, you end up with the overlay road hitting banks and hills because the approximation is varying from where the data Ortho4XP used.

An example of this was next to NZWN, a 4 lane highway in the overlay coasted with half it’s lanes up the side of a steep hill. Ortho4XP had the data of where the real road went and flattened it nicely in the correct place, but the Overlay was out and didn’t follow the nice path that had been created for it.

In the end, I actually edited the real data used by Ortho4XP to follow where the Overlay put the road. The road is still slightly off where it should be, but at least the terrain is levelled under the road, which is right next to the runway!

Using a 1 or 2 metre mesh means that you shouldn’t really need to artificially flatten the roads, because the resolution is so high that the road way will already be the correct geometry. Unfortunately, because the overlay data is such a rough approximation, you’ll find situations where the flat route of the road is nice and correct, but the actual drawn roadway from the overlay ignores it, and cuts right up the side of a hill.

Therefore, if you see some weirdness in the objects versus the ortho-photography and the mesh, that is why.

Oh and the UHD Mesh Packs are ready for release – totalling 69 GB including textures.

Categories: Flight Simulation

Tags: , , , ,

8 replies

  1. If only there was a way to take the OSM data and convert it to Overlay data. There must be a way to do that as that’s what the HD Mesh does. Maybe you could use their NZ Pro overlay instead of XP default?

  2. Looks like you can also use https://forums.x-plane.org/index.php?/files/file/33450-world2xplane-application/ to create overlay data from updated OSM.

    Should also be able to configure it to only use default objects so there is no need for any external libraries.

  3. A possible alternative fix is to make the overlaid roads transparent. I’ve recently downloaded something called Road & Autogen textures for Photoscenery 1.0.2 which claims to do this, but haven’t yet tried it. The installation instructions are opaque, to say the least. Will try it out on a backup XP and report back. But your new Overlay idea sounds much better. Also looking forward to cranking up the clockwork torrent and catch your latest enhancements!

    • Kinda but not really as the traffic will still travel on the XP roads…. which may not be aligned so, pick your immersion killer 😀

      • You are absolutely right, although the killing effect might not be too severe, bearing in mind that traffic in New Zealand is sparse outside the main centres, and there isn’t a single traffic light between the Picton Ferry and Christchurch. I’ll have a play with the transparent roads, but put my real money on a new bespoke overlay.


  1. The (Over)lay of the land – Lyndiman's Blog

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