Thanks to my foolish use of unprotected directories, we have basically announced that X-Plane 10 will feature global illumination. Here is some basic information on global illumination.
What Is Global Illumination?
Global illumination is the ability of any part of an airplane or scenery system to cast light on any other part of the scenery system or airplane. In X-Plane 9, the only lights in the sim that ever actually cast cast light anywhere else are:
- The sun.
- The airplane’s landing light. (Even if your plane has many landing light billboards, there is only one spill effect.)
- Three 3-d lights in the 3-d cockpit.
This list was kept short due to the high cost per pixel of each light on all rendering.
When X-Plane 10’s global illumination is enabled, a “spill” light attached to any OBJ can shine light on anything near it. Since any OBJ can have a spill light, this means we can have light sources on airplanes, scenery, cars, whatever you want. The spill effects any 3-d scenery nearby, even from another scenery pack.
This kind of still effect can be simulated in X-Plane 9 by careful use of LIT textures. However, real global illumination works between art assets created by separate authors. You can drive your custom airplane up to a custom airport and the landing and logo lights on the airplane will cast light on the terminal; the apron lights from the terminal will cast light on the airplane.
Furthermore, global illumination is fully dynamic – as objects animate or move, the lighting effects are correctly applied in 3-d. This makes effects possible that cannot easily be created using LIT textures.
Requirements for Global Illumination
Like most new rendering tricks in version 10, global illumination will be a rendering option that can be optionally enabled by users who have a video card meeting hardware requirements. In the case of global illumination, that requirement is a DirectX-10 generation video card, e.g. any Radeon HD , nVidia GeForce 8000 or 9000 series, and “100” series (100,200,300,400 series).
For authors: global illumination is applied using named and parametrized lights on your OBJ. Anywhere you can attach a light billboard, you can attach a spill effect as well, with some tuning constants for how wide you want the light, etc.
It will be possible to create two versions of your LIT textures, one to be used when global illumination is enabled, and one when it is disabled. Thus if you are baking lighting into your textures with a 3-d modeling program, you can simply re-bake the lit texture with some lights disabled and add 3-d lights to your model. The result is an airplane with real 3-d lighting where possible, and a close approximation via baking otherwise.
Global illumination can be added to a model incrementally; existing art content will work normally with global illumination enabled or disabled, so authors can choose to add a few light spill effects or add a large number, as time permits.
The Cost of Global Illumination
Global illumination isn’t going to be free. The main cost is an increase in VRAM use and fill-rate. The cost of global illumination is mostly a one-time cost to put X-Plane into a new rendering mode. (Graphics nerds: global illumination is implemented via deferred rendering.) The incremental cost of lights isn’t that high, although a scene with a lot of lights will have impact.
My expectation is that users with new, highly capable high-end graphics cards will be able to run global illumination easily, but will lose some of the other benefits of fill rate. (For example, running at 2560 x 1024 + 4x FSAA is a lot more painful with global illumination than without.)
Global illumination also introduces two artifacts, both of which I am trying to minimize as best as I can. These artifacts are a function of deferred rendering – all games that use deferred rendering have to address these problems:
- The lighting calculations are shared between multiple translucent surfaces, which can create some strange effects. For example, if a translucent window is in shadow, the scenery behind the window will appear to be in shadow too.
- Traditional full-screen anti-aliasing is not available with deferred rendering. We should be able to offer a simulation of 4x FSAA as well as some kind of cheaper FSAA-approximation, but the cost will be quite a bit higher in fill rate than the 16x-style CSAA available now.
(Hardware-based FSAA can make a number of optimizations like CSAA to optimize throughput; this is how such high multiples as 16x are possible. Since our implementation is similar to “super sampling” and costs a real 4x in performance, 4x will be the highest setting.)
Why Global Illumination
Of the new X-Plane 10 rendering engine features (and there are a fair number of them), global illumination is certainly the one that has the most impact on the structure of the rendering engine. With global illumination, X-Plane effectively has two separate modes (“forward” rendering, which is the only mode X-Plane 9 has, and “deferred” rendering, which produces global illumination).
One of the reasons to get global illumination done earlier than other features was that implementing global illumination required rewriting or modifying nearly every piece of low level rendering code. Now that the work is in place, we can safely add new features and test them in both modes.
Global illumination also meets two requirements:
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Sergio has long observed the central importance of lighting and shadows in the look of X-Plane; at some point more polygons and better textures still look synthetic without a realistic illumination model. Global illumination makes a more realistic lighting model possible at night. Airports represent an environment that can hopefully take advantage of such capabilities in a big way.
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As hardware becomes more powerful, authors have to do more work to create content that takes full advantage of the rendering engine. We are reaching a point where artist’s time is going to be a limiting factor as well as hardware and engine capabilities. Global illumination thus kills two birds with one stone: it makes the rendering engine’s output look better, but it also makes the whole scene look better with less work by the artist.
(For example, when baking lighting into a model, the author must plan the model’s texture UV map to guarantee unique texture space for all spill effects. When lighting effects are dynamic, the author can simply texture so the model looks good without worrying about baking requirements.)
There have been a few posts about X-Plane 10 in a few random places; here is a summary of all of the version 10 material that’s been previewed so far, and some notes on what is actually being shown.
First we had Paul’s Oshkosh 2010 video:
//www.youtube.com/watch?v=yCoDPNvOMP0?fs=1
I think this has been made clear already, but:
- The base simulator shown here is not X-Plane 10, it is X-Plane 9.
- Many of the airplanes shown here will be released for X-Plane 10.
- This is not showing the new X-Plane weather system or global lighting.
- Some of the content shown here are third party add-ons, available today for X-Plane 9.
The main purpose of this video was to show X-Plane off at Oshkosh; at the time we didn’t have X-Plane 10 in a state where we could do an exclusive version 10 preview.
Then I accidentally leaked two test videos of global illumination. This was strictly accidental: I was looking for a cheap way to post a large video for Austin and Propsman late at night and didn’t think anyone would sift through 191 zip files to find two obscurely named videos. I was wrong, and someone found them on the org. I appreciate that participants in the ensuing discussion withheld judgment; these were early test videos and don’t represent the final feature in any useful way. They do, however show off some of what global lighting will mean.
- This is the Cirrus Jet with landing lights implemented via global illumination. We get two distinct landing lights that cast specular hilights on the fuselage. As the door animates, it opens “into the light”.
- This is the Avanti Piaggio with strobes and beacons implemented via global illumination. The strobes cast light both on the fuselage and on the runway below the plane.
This second movie is typical of the kinds of tests I do: the beacon lighting is just awful – a gross huge red light splatted on the plane for test purposes. When I get the rendering engine code working I usually hand the feature off to Propsman or Sergio to tune the textures and art constants. In this case, the videos are pre-tuning.
Austin has posted three screen-shots of X-Plane 10-related content:
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This is Javier’s new shuttle, which I believe will ship in version 10. I believe this shot may have been taken in X-Plane 9. So this is not the new weather system.
Some of these screenshots and Paul’s video were shot in X-Plane 9. By the time the new airplanes are finished, they will not be usable in version 9 – they will be version 10 only.
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Propsman has done work on the lighting system. It can be subtle to see what’s going on here because the old runway lights looked pretty good too, but most of these billboard lights are actually rebuilt.
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This night shot shows global illumination in the scenery system. The glow on the highway pavement is not rendered; it comes from the 3-d lamps along the side of the road. Similarly, the car headlights spill light on the pavement and each other as they drive. (Note how the highway lines are visible in the headlight spill even when there is no streetlight.)
One difficult problem with rendering a lit highway at night is that the lighting from street lamps on a highway tend to spill light on the surrounding terrain, an effect that is impossible to create with a LIT texture. If you look at the right side of the main highway at the bottom of the picture, you’ll see that the street light is casting light on the grass to the right of the highway too.
I think that that’s all we have posted. At least, it’s all I am aware of. I will go into some of the details of global illumination in another post.
I’ve been working on road processing today; one of the tricky problems with OSM data is that, because an OSM map is often a collection of vectors from separate authors, the results can be a huge number of very small segments, as nearby road features from different data sources cross each other. (Basically you get “thrash” between the two vectors from different sources and our tools solve this by adding a huge number of extra vertices.)
I am trying to run this data through an algorithm called Iterative Snap Rounding (ISR) to reduce this mess of vertices, and for the purpose of this blog article there’s one thing you need to know about ISR: it is really, really slow. So for the next few minutes, I figured I’d start poking at some of the issues that came up at the X-Plane Congress in France this summer.
One question that came up was whether/when X-Plane will go 64 bit. Here’s my current thinking:
We can’t drop 32-bit X-Plane. Too many users have a 32 bit operating system, or a 32-bit CPU. One thing I have been resisting for X-Plane 10 is a ratcheting up of the system requirements to only top-end game machines. While 64 bit is becoming more prevalent and has the potential to be a big win for users who load the sim up with third party add-ons and have a high-end graphics card, plenty of people buy a computer first and then discover X-Plane. Those users will often have a system that is low end (by X-Plane standards).
If we start cranking the system requirements (you have to have 64-bit, you have to have a DX10 class graphics card, you have to have 2 GB of RAM) then more users who might discover X-Plane won’t even be able to run the demo, and that will be bad for X-Plane’s growth.
So the question is not “when will we switch from 32-to-64 bit” – it is “when will we support both 32 and 64 bit.”
I think we will get there during the version 10 run, but I don’t think it’s that likely that we’ll ship 64 bit right out of the box. 64 bit is more of a performance enhancement* than a new feature. The features we have strong motivation to get into 10.0 are:
- Anything that raises the system requirements, because we don’t want to raise system requirements after we ship in a free update.
- Anything that enhances the authoring SDK, where it might be useful for authors to know that every version of X-Plane 10 has a feature.
- Of course, we want to ship any feature that looks really good and gets people excited.
- Foundation features that support other featuers have to go in first. So some enhancements that will ship in 10.0 are there because without them other tech couldn’t be rolled out.
64 bit is important, but it is a feature that only helps some of the user base, and helps by making the sim more expandable; the sim is still usable without it. So we’ll get there, but new features are a zero sum game so I think 64 bit is more likely to be a free patch than in-the-box.
(At this point I expect the various 64-bit OS users who have been asking for a 64-bit app for years to flame the heck out of me and point out that I am a cranky old bastard who doesn’t realize that 64 bit is now everywhere and totally pervasive and that this is therefore the most important thing we could possibly do. Before you dig in, hang on one second, let me put on my asbestos flame-retardant jacket. Okay…fire away. 🙂
Oops…ISR just finished…with a seg fault. Gotta go!
* As a performance enhancement, 64 bit is a weird one; because a 64-bit app uses more memory for pointer-based structures, the same data structures become larger, thrashing on-chip caches more. The real benefit to 64 bits is to allow X-Plane to use more than 3 GB of physical RAM.
Austin attended the French X-Plane Congress last weekend; in response to some questions I have received, I want to clarify what is planned for DSF and X-Plane 10.
X-Plane 10 will extend DSF scenery capabilities by providing a number of new art asset types, as well as extensions to existing art asset file formats. We will not be changing the DSF file format or breaking compatibility with existing DSF scenery. If your DSF scenery works with version 9, I expect that it will work with version 10 as is.
(In fact, it looks like we do not even need to add new DSF extensions; DSF was designed to be a generic container for geometry data and properties, so we can usually extend X-Plane’s scenery system by simply defining new art asset classes and properties.)
An example will illustrate what I mean by extending the art assets, not DSF.
In X-Plane 9, you create a forest (whether in a base mesh or overlay DSF) by creating a DSF polygon referencing a .for (forest) art asset. X-Plane will render this by filling the area inside the polygon with lots of trees.
In X-Plane 10, you will be able to optionally tell X-Plane to put the trees only on the edge of the polygon, rather than filling the entire inside. (This feature will be controlled by using values on the polygon parameter that are larger than 255, at least I think.) This will mean that you can use .for files and DSF polygon not only to create forest areas, but also to create rows of trees along the edges of roads or fields. A row of trees made by a .for file and DSF polygon will render much faster than a large number of individual OBJ-based trees.
This kind of art asset extension is similar to what we have already seen; X-Plane 850 introduced three new art asset types (.str object strings, .lin line paint, and .pol draped polygons) that all produced new rendering tricks using DSF polygons. These art assets were added to provide high performance rendering of airport surface areas. The new art assets didn’t require any change to DSF because the representation of the position of these art assets is something DSF has always done: simple polygons.
DSF won’t last forever, but at least for X-Plane 10 it looks like we can do a third full cycle of the sim using DSF as our base container format for scenery position data.
REX is here for X-Plane. That’s really exciting to me because REX is a very successful add-on to FS X, and it’s been understandably difficult for us to convince companies that have a functioning and profitable business model on FS X to jump over to X-Plane, which requires building new capabilities in-house, starting at the bottom of the learning curve, and developing new processes. I hope these guys have a ton of success. Heck, I’d buy the product just because REXPlane is such an awesome name!
What surprises me is that we haven’t seen more ports of airport scenery. These packages can be partly converted mechanically using Jonathan Harris’ FS2XPlane tools, and in the case of an airport, the potential for recycling is huge – that is, the largest part of the development process is modeling, creating textures, and connecting the two. Since X-Plane can use these art assets with minimal mods, it seems like a very viable type of port.
With the latest updates to X-Plane for iPad, you can now purchase the Apollo lunar lander game inside X-Plane.
A quick note: if you lose your preferences (and thus X-Plane thinks you have not already bought Apollo) you will not be charged a second time if you click “buy it” again. When you go to repurchase Apollo, X-Plane will notice that you already have bought the upgrade and will simply re-enable the update.
Hopefully in our next patch we will make it clear in the UI that there is no double-purchase. The upgrade to Apollo is a “persistent” in-app purchase – once you buy it, you own it forever, as you would expect. (And because the iTunes store has a copy of your receipt, you don’t lose it even if your iPad or computer’s hard drive gets wiped out.)
Also, the latest update should fix crashes on iPads that were running for a while. X-Plane was very close to the memory limit so iPads that had been running for a while wouldn’t have enough free RAM for the sim. The new patch is a little bit leaner to work around this problem.
So all kidding aside, my iPad arrived today, and it is a pretty cool device. My normal attitude toward new gadgets is “great, more video driver bugs to fix”, but the iPad is exciting.
I’ll blog some other time about why I think the form factor is important and there is a spot for something bigger than a smart phone and smaller than a laptop.
For now I just want to point out that it flies X-Plane; X-Plane for iPad a bunch of new features, including 2-d panels while you fly, 3-d airports with full taxiway layouts, a completely rebuilt user interface, improved sky and water effects, and even some auto-gen buildings.
Also first impressions of the device itself: it’s really responsive. I have tried to surf the web with my iPod touch (which is based on first-gen iPhone technology) and it’s a tough experience – between the small screen, slow CPU and limited RAM. The iPad surfs the web like a desktop. A very light weight, portable desktop.
It goes without saying that this post was, um, inaccurate.
This, however, is real.
I wasn’t planning on discussing this until April 3rd, but some sites have already picked it up, so I might as well explain the why behind it. Simply put: X-Plane 10 will be for the iPad only. I figure that by letting you know now, you can make an informed decision about whether you want to buy an iPad. (Hint: you do!)
This wasn’t an easy decision to make, but here were some of the deciding factors:
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I spend a lot of my time debugging video drivers, and it makes me very grumpy. You guys seem to think that you can plug anything with copper and wires into your PCIe socket and call it a “video card”. By restricting version 10 to iPad only, we cut down development time by targeting only one GPU.
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We love everything Steve Jobs does and kiss the ground he walks on. Steve says the pad is magical.
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The biggest single feature request we get for X-Plane is “can I use X-Plane while operating a motor vehicle.” X-Plane 9’s requirement of 1 GB of RAM, a modern CPU, etc. means that most X-Plane 9 machines are not particularly portable. By making X-Plane 10 iPad only, we can provide X-Plane in a portable format that’s more compatible with flying a flight simulator while driving.
One fringe benefit to cockpit builders: because the iPad is so light and thin, creation of a realistic home cockpit with X-Plane 10 will be easier than ever. Simply take some super-glue, wipe it on the back of your iPad, and simply “stick” the iPad to whatever part of the cockpit you want. It’s so easy a four-year-old could do it!
A few days ago Austin made the recently cut X-Plane 9.45 “final” – that is, it is now the version you get when you update or grab a demo. This (hopefully) ends a sequence of 940 patches that represented a mix of fixing last-minute bugs and breaking and then fixing the throttles for a few add-on airplanes.
As always, if your add-on worked in an older version 9 but is broken in 945, please let us know. I believe the compatibility situation with 9.45 is pretty good though.
Will there be a 9.46? I don’t know, but I think the answer is: “probably”. I found a driver bug (occurs only on OS X) we can work around a few days after 9.45 was cut. We maintain a list of fixes, and when it starts to add up, we’ll cut a new patch to address them. Normally a driver bug would get a patch immediately, but from what we can tell, this one is very rare, so we’re not going to fire-drill and cut a new patch 1 day after 9.45 went final.
What kinds of bug fixes make it into these “bug fix patches”? To give an example, I received a report that the “clipping” checkbox on instruments is not preserved when you export an instrument as a text file. That’s the kind of thing we’ll fix in a patch, but we won’t cut a new patch immediately for.
