I have been working on visibility and fog-related bugs in X-Plane 10.30; two fixes will improve high-altitude long-visibility viewing:
- 10.25 has a bug where the fog color changes abruptly at the cut between DSF and planet rendering, particularly when atmospheric scattering is on. This is fixed in 10.30
- The 64-bit version of X-Plane 10.30 will load 12 DSFs instead of 6, for longer-range drawing of detailed DSF terrain.
These comparison shots show 35k above KSEA looking at Mount Rainier with max visibility. (Note that at 35k feet, it doesn’t make a huge difference what ground visibility you pick – the planet-wide upper atmosphere model is almost entirely in control.)
These pictures are taken at “very high res” – the most my Mac Pro can survive with an old GPU; you might get a little bit better definition on “extreme” res.
A few notes on loading more DSFs:
- My current plan is that the 64-bit version will always load the 4×3 DSF box – if we have to make this a setting for compatibility we will, but I think it’s preferable to not add more rendering settings.
- The 32-bit build will stay with a lower DSF count for memory reasons; generally speaking, I don’t think we will have any additional visibility improvements in the 32-bit build since we are almost always going to hit a memory wall. If you have a 32-bit OS, consider upgrading to 64-bits! (In particular, if you are running Windows XP, please upgrade to Windows 7 or 8 64-bit – there are no more service packs for Windows XP, so you’re just asking to get malware!)
- In 10.30 the DSF loader can load up to 4 DSfs at a time (for 4×3) or 2 at a time (for 3×2). So if you have a multi-core machine, the load time should be better even though there are more DSFs being loaded, thanks to multi-core. (The limiting factor here is that adjacent DSFs can’t be loaded at the same time because their edges need to be matched.)
I am still hoping to address other low-visibility fog issues, but that code is not complete yet.
The Planet Could Look Better
X-Plane renders nearby terrain using DSFs, but it renders the very far terrain and entire planet using a single “planet” model, which is a textured sphere displaced by a normal/height map. As of X-Plane 10.25 (and 10.30) we are not including as much detail in the 3-d planet mesh as the data on disk contains.
This pair of pictures is 45k above LOWI; the second texture has the mesh spacing on the planet artificially increased from 3 km to 2 km. (The data on disk is at 1 km spacing, but my machine can’t cope with that.)
You can see we pick up a little bit of definition in the far mountains. In the long term, I think we could ship a 500 meter planet mesh, which would make the far view in X-Plane as good as the close view used to be in X-Plane 7.
I’m not sure when we’ll ship a higher density far-planet, but I think it will have to be post-10.30.
If 1 km or 500m seems like bad resolution, do consider how far away the planet mesh is. With a 4×3 DSF box, the planet starts 100 km from the viewer. At 90 degrees FOV (an extreme case, but it makes the math easier) the screen is 200 km across at the DSF cut-over. With a 2 km planet grid, that means we will show 100 planet vertices left-to-right. At 1080p the planet triangles are thus at 20 pixel increments – not bad for a low res mesh.