Author: Ben Supnik

Crash Fixing, Airports, Photometric Lighting

It’s been very busy here internally, but a few things to mention.

X-Plane 11.55 – Crash Fix

We’re focusing almost all of our effort on future technology, but Stairport reported a bug severe enough that we went for a patch: X-Plane would randomly crash when plugins use the new “instancing” drawing APIs.

The instancing APIs are the Vulkan-compatible way to draw objects from plugins, the way to add particle effects via plugins, and will someday support sound as well. Simply put, instancing is meant to be the foundation for plugin-created dynamic content. Third parties did a great job of switching to instancing to be Vulkan compatible when we released X-Plane 11.50, so having this API be rock-solid is really important.

With X-Plane 11.55, correctly written add-ons should “just work.” The interaction between instancing and datarefs does sometimes confuse developers, so I’ll cover that in some nerdy detail in a future post.

The Latest Gateway Airports

While we were cutting a hot patch, we took another set of airports from the X-Plane Airport Scenery Gateway – 11.55 features over 1000 new 3-d airports and 443 brand new airports. I remain amazed at the Gateway community’s progress and results.

X-Plane 11.55 release notes can be found here.

What Is Photometric Rendering

I’m excited to finally be able to talk about something I’ve been working on for a while now – the new photometric lighting pipeline. Here’s the preview video Chris and Thomson made:

X-Plane’s lighting and rendering have leveled up several times – in X-Plane 10 we moved to HDR with global lighting, and in X-Plane 11 we introduced Physically Based Rendering.

I know this kills, but it’s too soon to talk about release dates. I can say a little bit about what you’re seeing in the video though.

First, the new lighting pipeline is photometric. What that means is that color values during rendering match real world values (in real world units) through-out the entire rendering process. Rather than say “1.0 is a bright thing, and, um, 4.0 is a really bright thing”, with photometric rendering, there are real answers. The sun is about 120,000 lux. The blue sky might be 8000 cd/m^2. A landing light on the 737 might be 200,000 candela at its peak intensity.

The idea behind photometric rendering is to have all elements of the scene be calibrated to real world values so they all match each other. That cloud should match that sky and that airplane because they’re all in the same units. No more tweaks to try to make things match.

We shipped an HDR renderer years ago, but the new pipeline is, well, more HDR. A lot more HDR. Because we’re working in real world units, we have to maintain a wide HDR image from beginning right to the very end when we tone map. The result is that every part of the scene can have a wide dynamic range.

While our shipping pipeline dims displays during the day by darkening them (to give the appearance of wash-out), the new pipeline simply draws everything in real world units – the camera is simply set for day time exposure (set in real EV units like a real camera) and the displays look dim due to the camera.

The new pipeline features a new tone mapper – one thing you might notice from the videos is that color with the new pipeline are richer. This is partly because the new tone mapper (which works well with real-world illumination values and is HDR-display-ready) does a better job of preserving saturation.

Sun and sky colors in the new pipeline are driven by a new atmosphere and sky simulation – they’re not painted textures. We get the sun color from the composition of the atmosphere and the relative position of the sun and scenery.

Finally, the new pipeline can run screen space reflections (SSR), dynamic exposure, bloom and other effects (still to be previewed), all running with real world photometric HDR values.

Why Photometric Rendering?

The photometric renderer gets us a bunch of visual quality improvements and new effects that were high on our TODO list (and, based on the feedback site, yours too.)

Photometric rendering also serves as a foundation for a bunch of other features that are high on our priority list. That will be a topic of a future preview and a future blog post.

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Departures and Arrivals, Lua Bug Fixes, G2 Controllers, and Stuff

Every week for the last ten weeks I’ve thought “I should really write a dev blog post” and then…not done that. This isn’t because all is quiet on the Western front – on the contrary, everyone on the team has been really, really busy, and the dev blog is never the loudest thing shouting for attention. But now we have a new RC available, so here we are.

Mi Memory Es Tu Memory

11.53 fixes one bug, and it’s a rare bug, but it’s “exciting” when it happens. It turns out that if a Lua plugin requests a really huge amount of memory, instead of saying “no,” X-Plane gives the Lua program someone else’s memory. This is not good! If the bank gave you someone else’s money, that’d be a bad bookkeeping error. This bug is too, and the consequences of the bug are typically “really insane stuff happens later,” which is hard to sort out. The plugin that crashes may not be the plugin that requested the memory.

X-Plane 11.53 fixes this – large allocations that cannot be fulfilled are denied, which should cause the Lua plugin to halt the affected script without destabilizing the system.

Script authors, if you’re wondering “now can I allocate a lot of memory in my Lua script,” the short answer is “no.” The longer answer is: when your Lua plugin uses a new version of LuaJIT that can use 64-bit addressing, this limitation will go away via a new plugin, without a change to X-Plane. Since the limitation is in LuaJIT, it’s out of our hands.

G2 Controller Support

Since we were doing a bug fix release, we have included support for the HP Reverb G2. For reasons I don’t fully understand, controller support didn’t “just work” in 11.52, so we had to create a new profile.

G2 users should be able to use their controllers with X-Plane 11.53. However you should also read our KB article for any additional issues with controllers, especially with misalignment. This version also includes a CLI option to adjust this if needed.

Tyler Has Left the Building

After almost seven years, Tyler has joined the ranks of Laminar Research alumnae. You may know him from such hits as:

  • The X-Plane 11 User Interface
  • X-Plane Mobile’s global scenery
  • X-Plane Mobile’s mass multiplayer

He will be missed! It took several weeks just to figure out all the things he maintains.

We Need More Jims

A few weeks ago, we posted a developer opening – I am pleased to announce Jim Keir as the newest member of the X-Plane development team. Jim is already fixing our screwed up code contributing bug fixes and learning the insides and outs of X-Plane’s almost 1 million lines of code. Jim brings our count of Jims up to two, which is still less of a namespace collision than our three Dan*s.

Multicore and Plugins

Most of what we are working on is still in the lab and hasn’t escaped yet. A few weeks ago we did have a discussion with developers in our third party developer Slack channel about multi-core and plugins.

The short story is this: in X-Plane 11.50, Sidney added a widget to the plugin admin window that shows how much main thread time they’re consuming, which in turn reveals how much each add-on is impacting FPS.

Plugin authors responded! Lots of plugins moved their CPU processing time to a worker thread. This is mostly great – other cores tend to be underutilized on high-end machines so this gets us more FPS.

Here’s the concern: a lot of plugins are doing this, and they are each moving work to other cores in their own private way. There is no coordination between plugins, and one day we are going to wake up and X-Plane will stutter because plugins were (just for a frame) using all of the cores and leaving too few for X-Plane itself.

We are looking at a mechanism for plugins to use the background processing system that X-Plane has built in. The win would be that X-Plane could play traffic cop between plugins and the sim itself, and prevent background plugin loading from causing frame stutters.

I will write up a Request For Comments (RFC) as a future blog post, so that a wider audience can comment on this.

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X-Plane 11.51r1 Now Available


The first release candidate for X-Plane 11.51 is now available. (Release notes here.)

Thanks to the users who filed bugs (especially Bill), we now understand the issues with the HP Reverb G2, but the fix is not in 11.51r1. The fix needs more testing than will fit into this patch. If you have an HP Reverb G2 and haven’t filed a bug, please do, so we can find you to send you a possible test build. In the meantime, we won’t hold up 11.51 and the new Gateway airports; rather we can work on the G2 in parallel.

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Help Us Find Those Devices

When we released X-Plane 11.51 beta 2 last week, we included up-to-date Aftermath support. Aftermath is an NVidia driver feature that catches detailed information when the GPU crashes (e.g. “device loss” crashes).

Full Aftermath debugging slows X-Plane down. The sim is still flyable, but you might go from 50 to 35 fps, for example. It’s noticeable, so we didn’t just turn Aftermath on for all eligible users. It’s too big of a perf hit to just leave it on all the time.

Unfortunately, while we know from auto-crash reporting that device loss errors are happening, we also know that no one is using Aftermath to capture detailed information that we could use to find and fix the potential problems in X-Plane.

So: if you hit device loss errors while flying with Vulkan on Windows with an NVidia card, please follow these instructions and run with Aftermath for a little bit. If you can drop us a few auto-crash-reports with Aftermath enabled, it could get us the key breakthrough we need to fix device losses.

Beta 3 Stuff

X-Plane 11.51 Beta 3 is here – here are the release notes. The most notable change is that we now have the new Gateway airports!

Tyler also fixed some low level networking bugs. This doesn’t change how multiplayer fundamentally works – if you can’t do a LAN flight across your WAN or you need command line magic to get the right NIC, that’s all still true and really not in the scope of what we’re fixing in 11.51. This whole beta run is targeted bug fixes.

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X-Plane 11.51 Beta 2 Bug Fixes

X-Plane 11.51 Beta 2 is now available. (Release notes here.) Here’s a few more details on bug fixes we are working on.

Device Loss Errors on Windows

A device loss error occurs when shaders running on the GPU crash. In the old days this might hang or blue screen your computer, but fortunately we live in the age of enlightenment – the GPU catches the error, stops running X-Plane’s shaders and leaves a note for the Vulkan driver to tell X-Plane “hey, you your code died.”

NVidia’s “Aftermath” is a diagnostic tool that can tell us why our shaders crashed on the GPU. When we tried to use it in the past it crashed, but NVidia has since updated their drivers, so we are trying again.

Aftermath can collect lightweight or heavy crash info; the lightweight crash info doesn’t hurt FPS, so it is now always on. Heavy crash info significantly lowers FPS, and must be turned on by the command line –aftermath flag.

So…we are looking for a few brave volunteers. If you:

  • Have an NVidia card with driver 457.09 on Windows 10 and
  • Sometimes see device loss errors during your flights and
  • Can live with some FPS loss for a little bit to fix these errors

Please run with

--aftermath
and auto-report any crashes that come up. If you get a device loss error with Aftermath running, the automatic crash report will contain all of the info we need.

Device Lost Errors on OS X

Device loss errors can happen on OS X in Metal, too – the mechanics are the same as Vulkan. We are aware of one AMD driver bug that caused them which we have worked around in 11.51b1. If you still see device loss errors in 11.51 betas, please file a bug, as we don’t have automatic reporting for these.

HP Reverb G2

We are looking into controller problems with the HP Reverb G2. In X-Plane 11.51b2, the grip trigger should start working again, but the default configuration will still be weird.

The problem appears to be that SteamVR identifies the first-gen and G2 WMR controllers the same way; we are still looking into this. If you have these controllers and haven’t yet sent us a bug report, please try them with 11.51b2 then send us your log with the additional diagnostics.

Clicking Settings Crashes on Windows

A few users have seen crashes when opening the settings menu on Windows, before ever turning on Vulkan. As best we can tell, the crash happens when we open the settings screen because we have to go inspect the Vulkan driver to see if it is usable, and that code goes off the rails. We have a possible fix for this; our theory is that it happens to users who have various third party “layers” (layers are basically plugins for the Vulkan driver) that have gone off the rails.

Gateway Airports

We are still fixing bugs in the Gateway airports export; it’s not ready for beta 2, but it should be in the next beta after this one.

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ARM Macs

On Tuesday Apple announced new Macs powered by Apple’s M1 chip, a custom ARM system-on-a-chip based on the Apple A-series System on a Chip (SoC) from the iPhone and iPad.

The rest of this post is probably only of interest to Mac users, but for Windows users, it’s worth noting that the M1 chip is fast. It targets laptop and low power use cases, not gamer-class hardware, and it’s not a discrete GPU. Here’s my 27″ iMac – Intel says the i9 in it is a 95W part:

Single core: 1265 Multi-core: 9414

and here’s a new M1-based MacBook Air, with 8 cores running at ten watts:

Single core: 1732 Multi-core: 7545

That’s…a pretty high score for Apple’s first trip into desktop land. One more for perspective:

AMD’s new Ryzen 5900X, which is a great chip, with a 105W TDP:

Single Core: 1619, Multi-core: 13656

The take-away here is that Apple doesn’t just have fast chips for their new machines, they might have the fastest ones.

Now, how is this going to work with X-Plane and plugins?

X-Plane 11 is an x86_64 app, as are all plugins ever written for it. So if you run it on an Intel Mac, it just works, and if you run it on one of the new ARM Macs, it will run using Rosetta, which will translate the code as you fly.

In the future, we will have an X-Plane build that is “universal”–that is, it contains ARM and x86_64 code, and we will have a plugin SDK that contains both ARM and x86_64 code. At this point, plugin authors can start recompiling plugins to contain both types of code as well. Users with ARM Macs will have the choice to (1) run ‘natively’ in ARM for higher performance and use only plugins that are universal or (2) continue to run x86_64 code under Rosetta, so that all plugins work.

(This option is available for all apps that are universal on an ARM Mac – you turn “Use Rosetta” on or off in the app properties.)

This situation is exactly the same as the PPC->x86 transition we went through years ago.

Plugin developers: once Big Sur and the new X-code are out and we have an ARM plugin SDK, you can add a new architecture to your project and that should be it, as long as you don’t use any x86 assembly code in your add-on.

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Stuff We Are Working On

It’s been a while since I have posted about what the team is working on, and given all that has happened in the last few weeks, it feels like a million years. Here’s a run-down of…stuff.

X-Plane 11: Beta Time

Today we are putting out X-Plane 11.51 beta 1. This is a bug-fix patch for X-Plane 11.50 with a handful of random fixes that we have accumulated over the last few weeks. Release notes here. You will not be auto-notified of this beta–you have to pick it in the installer if you really want it.

I expect the beta to be relatively short, as we’re just trying to put out fixes for things we’ve found since we’ve shipped 11.50, improve diagnostics, reduce crashes, etc.

11.50 beta 1 does not have new Gateway airports. We’ll include them very soon–probably in beta 2–we had a few last minute snags, so I pulled them out of beta 1 to avoid delay.

Road Map: Graphics and Performance

X-Plane 11.50 represents the first step in our long term performance road map: moving to modern, low overhead, high-performance rendering APIs. These APIs are multi-core friendly; for X-Plane 11.50 this results in better overall FPS and smoother performance, but only an incremental increase in multi-core use.

One stealth performance feature in X-Plane 11.50: plugin object instancing. X-Plane has had an instanced drawing API for several years now, but with 11.50 we saw widespread plugin adoption. This is going to be very important for performance going forward; the instancing APIs are designed for efficiency, particularly in a multicore environment.

We have now switched gears and we are working on new features in the engine itself, e.g. we are working on what we draw and not so much how we draw it. In other words, we are working on graphic enhancements, new features, etc.

The new features are, as they are being coded, already taking advantages of new tech made possible by Vulkan and Metal, e.g. GPU compute kernels, GPU-based culling, etc.

Once we finish rendering features, we can pivot back to performance and push hard on multicore. The next multicore goal is to be able to render multiple views in parallel using multiple cores. Parallel rendering has several benefits:

  • An X-Plane frame often has sub-views rendered to form the main view (e.g. shadows, water reflections, cube maps, in-cockpit cameras, etc.). Any concurrency we expose makes the sim faster in these scenarios, and they are common.
  • Right now while multi-monitor is possible with X-Plane, it is very expensive performance-wise. Having a frame that can be farmed out to multiple cores would make multi-monitor less of a performance hit.

Note that multi-core multi-monitor would still be single GPU, and it would be a win because right now CPU time limits multi-monitor setups.

What about multiple GPUs? That’s something we’ll have to look at after we have multicore on the CPU–without it second GPU support doesn’t help.

Big Sur & the Mac

There’s been a lot of Apple news this week that’ll have to wait for a separate post. We recommend waiting on Big Sur for a few days until we’ve had a chance to test it a bit. Hopefully that’s an easy ask, as right now the download servers appear to be overloaded.

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Where to Send Feature Requests

Back in the day, the way you put in a feature request for X-Plane was to email Austin – his email address was all over the website. So was his phone number – if you really wanted the request you could just call him, but it might hurt your chances. Austin had a big text file where he copied all of the emails, and then he randomly jammed things into X-Plane. It was the wild west.

Fast forward twenty years – we have a development team, we have customer support, we have an art team, and X-Plane has a lot more users than it used to. So we made an official place to record feature requests: feedback.x-plane.com.

The feedback request board allows for voting, so please look through the existing requests and up-vote it if it’s already there–this lets us easily find very popular requests.

The request board covers X-Plane desktop and mobile. You can also request features for end users (“better clouds”) or for third party developers (“scenery packs can edit the mesh around airports”)–it’s all good.

Looking through the “most wanted” right now, it looks like our internal high priority items (most of which are in progress) match the most wanted list pretty well, which I think is a good sign for our upcoming dev work.

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X-Plane 11.50 Is Here

X-Plane 11.50 quietly went final yesterday. Very quietly.

We’re trying something new with this release: a phased roll-out. Here’s how it works:

  • 11.50 is final – if you run the installer and request updates, you’ll get 11.50, regardless of whether you check ‘get betas’.
  • Only some users are being auto-notified of the update.
  • Over the next few days, we’ll slowly crank up the number of auto-notifications until it is everyone.
  • Steam users: you still have to opt into the beta – we’ll mark the Steam 11.50 version as final probably tomorrow.

We are trying the phased roll-out to make sure support doesn’t get overwhelmed; some add-ons need to be updated for 11.50 compatibility, and we didn’t want Thomson and company to go down the tubes helping users get their add-ons updated.

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