If you have content that worked in 864 but does not work in 9, please file a bug! Please do not assume we intentionally changed the file formats to break compatibility…I would rather get the bug report so we can fix X-Plane than have you change your work.
For every author who changes his or her work in response to a bug (an accidental breaking of compatibility), we’ll have dozens of users who find their add-ons not working but not knowing how to fix it themselves.
With that in mind, beta 16 will have two fixes:
- Some panels were showing the default instrument backgrounds over custom panels. This will also be fixed in the next beta.
- Lit customized overlay parts were not showing. This will be fixed in the next beta.
So if you see those bugs, please check your plane against the next beta when it comes out. If you find other problems, please file a bug!
X-Plane 8 didn’t care much whether you used ATTR_cockpit in scenery objects or other strange places. It would simply show the cockpit panel texture, and if it hadn’t been updated, you might see an old one, and if it had never been used, maybe you’d see the random (but colorful) contents of memory. Similarly if you could get close enough to another airplane to look in the window, you’d see your own panel, since there is only one panel texture (for the user’s airplane) in the entire scenery system.
This is a bigger problem in X-Plane 9.
- Because the panel texture can be expensive for big panels, we are a lot more aggressive about not setting up the panel texture if we can avoid it. This means that sometimes the texture doesn’t exist at all. This is why in beta 14 you get an error if you do a formation flight having only been in “w” (forward 2-d) view…the panel texture doesn’t yet exist, but the exterior view of the Cessna tow plane uses it.
- With panel regions there can be up to four panel textures, so you can see the potential for anarchy.
- Panel textures aren’t even the same size any more, causing the wrong-panel-in-AI-plane problem to look even weirder than before.
So in beta 15, the panel texture is replaced with a dummy white texture for:
- Any cockpit object for an AI plane.
- Any scenery objects that are illegally using the panel texture.
This prevents crashes and other nasty stuff. If you want to make the panel be visible in your AI plane, consider using LOD to make a non-panel-texture “fake” cockpit image (at a very small res) at farther LODs. My guess is that in normal usage of the sim you’d really have to do something dangerous to get close enough to see the hack.
We did discuss live panels for all planes (for all of about 3 seconds), but the live panel texture in 3-d is so expensive that it’d be prohibitive to most users for even one AI airplane, let alone 20!
If you create plugins, airplanes, or scenery for X-Plane and haven’t tried your add-ons with X-Plane, please do so soon!! It’s much easier for us to fix backward-compatibility problems while we’re still in beta. Beta 14 introduced some bugs (that should be fixed in beta 15 real soon) but I think we’re reaching the point where you can do compatibility testing.
We’re working on a public Linux beta – see here.
Brett and a few other users pointed out to me that the nVidida ForceWare 169.21 release appears to hose video for X-Plane. If you have an nVidia card, don’t update, or you may want to back up a version.
This kind of thing has happened in the past – hopefully a revision will come out fairly soon. (But I do not have contact with the nvidia driver team for Windows on this…)
Also some users are seeing corrupt startup screens with ATI hardware – apparently some configs don’t react well to us turning vsync off. Not quite sure what we’ll do about that yet, but hopefully a fix will be in the next few betas.
We’ve been preaching “one big texture, not lots of little textures” for a while now, and generally speaking, packing a lot of art into one big texture makes life eaiser for X-Plane, because it can draw more triangles at once before it has to tell the card to change what it’s doing. Inside the company we call this the “crayon rule“.
Now the total set of geometry and textures that X-Plane needs to use for one frame is the “working set” – you can think of it as the crayons that you keep out of the box because you need them all the time. And as I said before, if the working set becomes too big, your framerate dies.
Now with large panels we’re seeing a new phenomenon, one of the first cases where the crayon rule might not be true. The reason is due to working set.
When you make an airplane with a large panel in version 9, you can either use ATTR_cockpit, which lets you use the entire panel as a texture, or you can use ATTR_cockpit_region, which will let you use several parts of the panel. Each ATTR_cockpit_region is a texture change, so that’s more crayons. And yet ATTR_cockpit_region is usually faster.
The reason is two-fold:
- You can often use cockpit regions that don’t cover the entire cockpit texture. Large panels are rounded up to 2048 if the are larger than 1024 in any dimension, so the “wasted space” in a 1600×1600 panel is actually quite huge. If you can get away with some smaller regions, your total panel texture area is smaller because there isn’t wasted space due to this rounding, and you can also skip things like Windows. Prepping the panel texure takes time, and it’s done once for lit and once for non-it elements, so it adds up!
- It turns out there are two categories of textures that contribute to the working set: static texures and dynamic ones, and their impact on VRAM is very different. Dynamic textures are much more expensive. The panel texture is dynamic and it’s uncompressed, so it really costs a fortune. (32 MB of VRAM for 1600×1600. That’s not a lot for a static texture but for a dynamic one that’ll kill you.)
Here’s the details on dynamic vs static textures: the OpenGL driver keeps a backup copy of a texture in main memory, so that if it has to purge VRAM (to make room for more stuff) it still has the texture. As it “swaps” textures, the process is to simply send textures as needed from main memory to VRAM. No big deal.
But with a dynamic texture, the texture has been modified in VRAM! So the copy in system memory is old and stale. The graphics card thus must send the texure back to main memory, consuming twice as much bus bandwidth as normal. (To free 16 MB of VRAM and refill it takes 32 MB of transfer, 16 MB to copy the old texture back to system RAM and another 16 to send the new textures to VRAM.) On non-PCIe cards, this back-transfer might be at 1/8th the speed of the transfer to the card, so this is even worse on AGP cards.
Thus the driver does its best to not throw out dynamic textures. And this is why the panel texture is so expensive. That P180 will cause X-Plane to make two 16-MB dynamic texures, and those textures will cause 32 MB of VRAM to basically be off the table. That’s less space for the other textures to swap in and out of. This kind of “permanent allocation” makes the VRAM budget tighter for all other drawing operations.
Given the right combination of large panels, large res, pixel shader effects (which make more dynamic textures), clouds, and FSAA, you can easily get even a 256 MB card to a state where the free space into which static textures are shuffled becomes horribly small, and the framerate just dies.
So the moral of the story is: yes, it can be worth 4 crayons (using panel regions) to avoid the huge cost of dynamic textures from large panels.
As to static textures (regular DDS files) that are 2048×2048 – the jury is still out but my guess is they don’t represent a huge performance problem. As one user pointed out to me, they’re only 2 MB when compressed (maybe more with alpha) so they’re not insanely huge, and they can be swapped out.
Lori and I are about to leave for a New Years Eve ski trip, but before I shut down the laptop for the last time in 2007 I wanted to say: Happy New Years to everyone in the X-Plane community. I had a lot of fun working on X-Plane in 07 and hopefully the sim brought you enjoyment too. I think 2008 is going to be very exciting – version 9 plants the seeds for a lot of interesting new possibilities during the version run.
When I get back I’ll post a bit on panel regions, for which I have the first performance numbers, as well as some of the strange effects FSAA has on the sim. We should have a progress report on Linux soon too.
See you next year!
Sometimes we find that users machines cannot run without hiding OpenGL driver features from X-Plane. That is, the computer says it can support VBOs, but when the sim asks for a VBO, something really bad happens. X-Plane (since mid-version 8) accepts a series of command-line options that cause the sim to ignore the given feature.
These kind of bugs come and go as drivers are updated, the sim changes which technology it uses, and hardware cycles through the user base. The biggest one we’re seeing right now is that the new iMacs show runway lights as white squares unless the sim is run with the –no_sprites option.
We’re trying a new way to address these problems. In the past we would give users the command-line option; now we are building double-clickable script files that launch the sim with the appropriate options. Theoretically this…
- Is less error prone for users.
- Is quicker for users who may have to use the command-line option every time they launch the sim until a driver update becomes available.
- Is quicker for us (in that we spend less time mailing out instructions and helping users who are unfamiliar with a command-line environment).
We did consider some other options, but this seemed like the least evil. The runners-up:
- Just turning off the hardware feature permanently. We ruled this out because the performance hit would be significant and affect all users.
- Attempt to identify and auto-turn-off known bad options. We do this in some cases, but it requires changes to the sim code, so this does no good if a new video card comes out after a given x-plane release and introduces new problems. so it’s not a total solution. Also since a bug might be resolved in-field, if X-Plane auto-avoids certain configurations we have to patch the sim once the configuration starts to work again.
- Provide a user interface to turn these options off inside the sim. This was ruled out for two reasons: first, some of these options cause the sim to crash before a user can ever get to the rendering settings. Second, turning off these kinds of options can really kill performance, so leaving the options in sight produces a whole new tech support option. (A user tells us their framerate is awful at the lowest settings…perhaps they turned off the hardware acceleration options in an attempt to get the lowest settings…etc.)
We’ll see how well this approach works. So far it seems to be working better than handing out command-line options.
(Of course if we can address the problem by working around it with a change to our code, we almost always choose this option.)
In X-Plane 8 the global scenery was installed in the “default scenery” folder, which normally contains most of the built-in artwork to make X-Plane (and the global scenery) work.
In the X-Plane 9 beta it is installed in the custom scenery folder. But the sim recognizes it by name and makes sure custom scenery is higher priority than global scenery. This is imperfect but works. In the future we may do something different. Survival tips:
- The log file tells the priority of all scenery packages.
- Don’t rename or move the global scenery – leave it where it was installed.
- Custom scenery will always trump global scenery.
In X-Plane 9, road networks can be in DSF overlays. And in X-Plane 8 or 9, road types can be customized using a road.net file.
Within the road definition file, each road type can contain:
- “Segments” (textured quads that make the roads)
- Objects (placed along the road)
- Wires (for powerlines)
- Car lanes (that vehicles drive along)
The interesting thing is: none of these types are mandatory. So you can use any of these features without the others.
“Cars” are just objects too. So one way to make a vehicle drive around an airport would be:
- Create a road definition file with a new road type. That road type only has a car lane which references your vehicles OBJ model.
- Make an overlay DSF with this new road type, drawing the path the vehicle OBJ will randomly take.
- Package the overlay, .net file, and OBJ all together and you’ve got randomly generated vehicles moving around.
As Marginal pointed out on the .org forums, roads are currently not draped, so using them in overlays is a total PITA. This is something I hope to address in the 9.1 time-frame…draped roads are an important feature, but a little bit too invasive for the v9 betas.
I found the root cause of another NVidia specific bug, and once again it’s my own stupid code. If you Google for driver bugs, you’ll find plenty of grumpy developers ranting about how card X does this wrong thing and card Y does that wrong thing…I figure it’s only fair to follow up and say “yep, that one was mine.”
Like the previous nVidia-only crash, this was a case where X-Plane was always doing something wrong, but only some drivers had problems with the behavior. So the crash was NVidia-specific, but X-Plane caused.
I believe that this bug was manfiesting itself either as a message that “scenery shift took more than 30 seconds” or some kind of crash. One of the problems was that the diagnostics for this particular bit of code were really bad. So we’ve improved things a bunch…
- There is more careful error checking during scenery shift, and those error messages are reported.
- If the sim does crash, some new code will output a crash log on Windows that helps us isolate what actually happened.
Beta 12 will be out soon with the fix that caused problems on NV hardware as well as the improved diagnostics. So you may find that the sim just works better, but if it does still crash or report errors, please tell us – now we’ll have log files that will let us diagnose the problem a lot faster!
