Tom has a new video on youtube of his just finished Falco. The video shows what screen-shots cannot: that the mouse interactions on the plane are really well crafted.
If you’re just discovering X-Plane (or just discovering that X-Plane’s 3-d cockpits can be very interactive), here’s X-Plane’s “raw” capabilities for manipulation:
- The simplest manipulations are based on mapping the mouse from the 3-d cockpit back to the 2-d panel. This can only be done when the 3-d cockpit is textured using a piece of 2-d panel. This is the oldest way to make a clickable cockpit in X-Plane, dating back to the original X-Plane 3-d cockpits. The advantage of this method is that it’s very easy to set up; the disadvantage is that the mouse click gestures tend to be “flat” in their operation.
- As Tom’s plane demonstrates, you can manipulate just about any dataref or command via a drag along a specific axis. Axes are subject to animation, so there’s a lot of potential for “grabbing” things with this interface.
- X-Plane also supports direct “click” manipulation – this can be handy for buttons where you don’t want to require the user to move the mouse around. There are several types of click manipulation.
Click and drag manipulations can be tied into the plugin system – your plugin sees a manipulation as a change to a plugin-created dataref. This makes it possible to create almost any imaginable mouse effect. If you don’t want to write a plugin, you can still write up the manipulators to any of X-Plane’s datarefs (there are thousands) or commands (we’re getting up toward the 1000 mark on these too).
To create manipulators on your cockpit, you can use the latest plugin for AC3D. A manipulator is a property on a mesh within your object – each mesh can have its own manipulation with its own properties.
X-Plane does not have an IK solver. Rather, movement of “stuff” in your cockpit is indirect.
- Your manipulator changes a dataref as the user drags along an axis.
- The dataref change shows as an animation on your mesh.
Fortunately, ac3d has a “Guess” button for the axis manipulators. If you set a mesh to be manipulated by dragging along an axis, the guess button will examine your animations and suggest an axis that will create the most “natural” looking animation for the manipulation. For example, if you have a throttle handle that rotates, the guess button will provide a drag axis perpendicular to the throttle (to push the levers); if you have a throttle lever that pushes, the guess button will make a drag axis that runs along the lever.
I’ve been on the road a lot for work, so my apologies to everyone whose email I am sitting on. Most of my time these days is being spent on new next-gen tech. But there are a few things I’m hoping to get done in the short term:
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Cut a new time-demo test. This might seem like a low priority item, but it’s not. Apple, ATI and NVidia all run continuous automatic tests of their video drivers, with many applications and games. They have rooms full of computers that continuously run through 3 minute sections of Quake and Call of Duty, etc. If they introduce a driver bug while doing new development, these machines catch the problem immediately.
The new time demo (based on 945) will have a number of features to make X-Plane a more useful test case. If we can make X-Plane into a test case, then they can catch bugs early, and that means you don’t have to see them.
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Bring WED 1.1 to beta. The only thing holding it back is the DSF exporter, and I did have about two hours to poke at it last week. I’m hoping if I can find just a few more hours, I can finish off the exporter.
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Examine 950 bugs. I have half a dozen bug reports against 950 beta 1. 950 will be a small beta but also a slow one, because Austin and I have a lot of other things on our plates. If you haven’t heard back from me on a bug report, probably it’s still on my to-do list.
We’ll see how much of that I can get to in the next week.
There’s basically one reason why WorldEditor developer preview 2 is a “developer preview” and not a real beta: the DSF overlay export code isn’t complete.
The problem is that, unlike an airport, an overlay has to be “cut” to the DSF tile boundaries. This is made slightly tricky by the fact that the overlay can have (1) bezier curved segments and (2) a UV map on those segments. My existing toolkit of polygon editing routines doesn’t handle this case yet.
I have no idea when I will have time to complete this code. It is the number one piece of code that, if I had a quiet single afternoon of unexpected time to code, I’d pound it out. If I were stuck in an airport with my laptop, I’d pound it out. It should give you some idea of how busy things are that it still isn’t done.
In the meantime, there is the scenery tools bugbase. By filing a bug, your issue won’t get lost even if it’s a while before I get to it.
A few quick rants about the bug base:
- Most likely the first thing I’ll do when I do get to your bug is just ask you for more info. Consider the bug to be as much a business card so I can make contact as well as a bug report.
- Some bugs may get kicked out.
- Do not file X-Plane bugs in the scenery tools bug base! The scenery tools bug base is not where we store sim bugs.
Do not bother to ask for direct bug base access for X-Plane itself. You cannot have it. The ratio of submitted “bugs” for X-Plane to actual bugs is at least 10:1. That is, 90% of you think that you should file a bug when you have a tech support question. Now you might be in that 10% (particularly if you’ve made it all the way down to this blog post), but we can’t set up open infrastructure with those numbers. My hope is that the scenery tools are self-selecting to the point where people who are using developer-preview tools know what a bug report is.
The file loading code in 950 beta 1 for Windows is slower than 945. Sometimes. This will be “fixed” in beta 2. Here’s what happened:
The scenery system uses a number of small files. .ter files, multiple images, .objs, etc. This didn’t seem like a problem at first, and having everything in separate text files makes it easier to take apart a scenery pack and see what’s going on.
The problem is that as computers get bigger and faster, rather than a scenery pack growing bigger files, they are growing more files. The maximum texture size has doubled from 1024×1024 to 2048×2048. But with paged orthophotos, multicore, and a lot of VRAM, you could easily build a scenery pack with 10,000 images per DSF.
That’s exactly what people are doing, and the problem is that loading all of those tiny files is slow. Your hard drive is the ultimate example of “cheaper by the dozen” – it can load a single huge file at a high sustained data rate. But the combination of opening and closing files and jumping between them is horribly inefficient. 10,000 tiny .ter files is a hard drive’s worse nightmare.
In 950 beta 1 I tried to rewrite part of the low level file code to be quicker on Windows. It appeared to run 20% faster on my test of the LOWI demo area, so I left it in beta 1, only to find out later that it was about 100% slower on huge orthophoto scenery packs. I will be removing these “optimizations” in beta 2 to get back to the same speed we had before. (None of this affects Mac/Linux – the change was only for Windows.)
The long term solution (which we may have some day) is to have some kind of “packing” format to bundle up a number of small files so that X-Plane can read them more efficiently. An uncompressed zip file (that is, a zip where the actual contents aren’t compressed, just strung together) is one possible candidate – it would be easy for authors to work with and get the job done.
In the short term, for 950 beta 2, I am experimenting with code that loads only a fraction of the paged orthophoto textures ahead of time – this means that some (hopefully far away part) of the scenery will be “gray” until loaded, but the load time could be cut in half.
There is one thing you can do if you are making an orthophoto scenery pack: use the biggest textures you can. Not only is it good from a rendering perspective (fewer, larger textures means less CPU work telling the video card “it’s time to change textures”) but it’s good for loading too – fewer larger textures means fewer, larger total files, which is good for your hard disk.
(Thanks to Cam and Eric for doing heavy performance testing on some of the 950 beta builds!)
Life would be easier if the Earth was a big cube.* I was reminded of this yesterday when I discovered (thanks to a bug report from an author) that X-Plane has been drawing objects with slightly incorrect heading for the last who-knows-how-long amount of time.
The bug (present in 945 and going back who-knows-how-long) is that the object’s heading can be off by up to 1 full degree clockwise or counter-clockwise. (This maximum error occurs at the north pole – average error for real use cases is more likely to be about 0.35 degrees.) The amount of rotation depends on how the scenery system is shifted.
The case the author sent me was a converted scenery pack, where a pair of parallel runways were modeled partly out of draped polygons (which don’t exhibit the bug), but with markings modeled as an OBJ. Depending on the scenery system’s “centering” the markings would be a little bit to the left or right of the draped polygon.
A brief aside: do not model your scenery this way! A bug is a bug, and X-Plane 950 beta 1 fixes this problem, but there are a number of reasons not to use a giant OBJ to model your runways.
- OBJs do not “hug” the terrain, and the Earth is round. You will never really get clean, artifact-free flat surfaces unless they can follow the terrain contour. Even if you “flatten” the terrain, it’s not flat – it’s constant MSL.
- The case where I see this more often is with buildings, where authors build every single terminal building in one OBJ. X-Plane only “connects” the OBJ to the ground at one point (0,0,0 in the object). So to get a good ground connection, you need your objects to be smaller, so they can all “sit” on the ground. (Technically they need to be rotated slightly to wrap around the Earth, but for the scale of an airport this error is only about 1/30th of a degree or so – hard to see.)
- Finally, X-Plane chooses to draw or not draw an object on a whole-OBJ basis. So if you have a huge object, it’s always in view (because at any one time some part of it is in view). In fact, even if the object is not in view, the larger the object, the more the “sloppiness” of the visibility check causes false positives. (The visibility check is optimized for speed, so it really answers “this object is probably in view”, erring on the side of drawing too much by doing less analysis.) So the bigger your objects, the more they are drawn.
Enough ranting – in this case the scenery was the output of FS2XPlane, and the author hadn’t gotten to cleaning the results. Fortunately the interim product showed the rotation bug.
X-Plane 950b1 (in beta now) fixes this problem – rotational alignment of a very large OBJ with a draped polygon should match between X-Plane (with all frames of scenery system reference) vs. WED 1.1 preview 2 pretty much exactly.
*This post is in the long and distinguished tradition of “life would be easier if” musings relating to scenery, e.g. global scenery would be easier if the entire planet was paved in asphalt, cities would be easier if their road grids only ran perfectly north-south and east-west, clouds would be easier if they weren’t translucent, and rendering would be easier if nothing on the planet ever was translucent or cast a shadow. So apparently a programmer’s paradise is somewhere between “Mad Max” and a Dali painting…
There’s a slight performance win to be had by grouping taxiways by their surface type.
Now clearly if you have to have an “interlocked” pattern of asphalt on top of concrete, on top of asphalt, this isn’t an option.
But where you do have the flexibility to reorder, if you can group your work by surface type, X-Plane can sometimes cut down on the number of texture changes, which is good for framerate.
X-Plane will try to do this optimization for you, but X-Plane’s determination of “independent” taxiways (taxiways whose draw order can be swapped without a visual artifact) is a bit limited and can only catch simple cases.
For what it’s worth, interlocked patterns of surfaces were much more a problem with old X-Plane 6/7 type airport layouts, where the taxiways were sorted by size, and there could be hundreds of small pieces of pavement.
Some of the newer text file formats for art assets (.lin files, roads, etc.) require you to specify how wide the texture is.
Huh? Why does X-Plane need me to tell it how wide a texture is? Doesn’t it know?
Well, first, the answer is: no! When X-Plane builds the roads and draped lines, the texture that is needed may not actually be loaded. It may only be on the todo list of textures that need loading, and if you have orthophoto scenery, that list could be very, very long. There is no guarantee that the texture is loaded before the geometry gets built. If you have a multicore machine, both might happen at the same time!
So the first reason why the road and .lin files require you to declare the size of your texture is: to allow X-Plane to build the mesh on a separate core from the one that loads the texture, for faster loading. Isn’t multi-core fun?
There’s another reason, and it’s a little bit more subtle: you can change the size of your X-Plane textures. Imagine that you get a new graphics card and you decide to “upgrade” your scenery pack. So you double the size of all of your textures, and then go in to photoshop and add more detail.
But if X-Plane were to look at the size of the texture, then all of your .lin files will be wrong! For example, let’s say you have a .lin file with a line from pixels 0 to 16 across the texture. When you double the size of your texture, you’d have to go in and change this to be 0 to 32 pixels across the texture.
But here’s the trick: since X-Plane gets the size of the texture from you and not from the actual texture, you can just leave your .lin file the way it was – with the old texture size and the old coordinates. X-Plane will do the math out and generate correct texture mappings even though the texture size is double.
In other words, the important thing about texture coordinates is that they are self-consistent, not that they reflect the actual texture size. This is because internally all texture mapping is done in ratios.
(So why not just use ratios in the file format? Try entering the size of 10 or 12 lines as ratios and tell me whether you like it. The ability to enter the line coordinates in pixels is to make it easier to set up the line files from the image file.)
Periodically I see the question asked: why does the global scenery take up so many DVDs? Or more typically the question is: if it is so big, why is X missing, where X is the detail the user expected to see but did not find.
The size of X-Plane’s global scenery is due to two factors:
- Some aspects of the scenery are very detailed, and this takes up disk space.
- Some aspects of the scenery are computed ahead of time, not by X-Plane, and this takes up disk space.
Big Data
A few data sources make the scenery pretty big:
- The scenery is generated from 90m SRTM data for the entire world.
- US scenery includes the entire US road grid.
- Coastline data is fairly detailed in the US and for most oceanic coasts.
In other words, part of the size of the scenery comes from having reasonably accurate topography and coastlines everywhere.
Precomputation
The other source of file size is that X-Plane precomputes aspects of the scenery to reduce load on X-Plane while you fly. (We do this to improve frame rate.) In particular, the scenery uses a class of algorithms that are expensive to compute, and thus we compute them ahead of time and save the result (using up file space).
- Land class changes not on a regular grid, but along iregular polygonal boundaries following the shape of the terrain. This produces much more natural terrain transitions in the mountain, but requires more storage.
- “Auto-Gen” forests and buildings don’t follow a grid – rather, they fit into the irregular spaces made by vector roads and water. This fitting process is too slow to run inside X-Plane, so every auto-gen building and forest area must be pre-computed and saved.
Room To Grow
One interesting side effect of saving the end results of building locations (“pre-placement”, what X-Plane does) rather than the formula for how to place them (“auto-gen”, what FS X does) is that we can make the placement algorithm for buildings significantly smarter without any increase in file size or decrease in frame-rate. Having already eaten the cost of putting every building into the DSFs, we can make those locations better without hurting performance.
That algorithm to pre-place buildings also can have access to source data that isn’t available in the final DSF, allowing for effects that might not be possible in an auto-gen system.
I just finished fixing some bugs with WorldEditor and DSF precision. A WED user was seeing draped polygon tiles exporting with alignment error, and the culprit turned out to be DSF precision. This begs the question, how precise are the lat/lon coordinates in a DSF?
DSFs are based on 16-bit coordinates, for a precision of one part in 65536. Now before you go screaming that 16-bit is dreadful, here’s the key: those 16-bit coordinates are interpreted within an arbitrary sub-rectangle of your tile, called a “pool”. If we only had one pool covering the DSF we’d have 1.5 meter precision. But by having many smaller pools, we can have high resolution within a pool.
All of the current DSF writing tools from Laminar Research are based on DSFLib, and DSFLib will create a number of pools along a pair of offset grids. In practice what this means is that you specify a number of pools across the DSF.
In WorldEditor 1.1dp2 the DSF exporter uses 8 pools. Since a DSF is about 100 km across, each pool is 12,500 meters in size, and the internal resolution of each pool is 19 cm. This is pretty good but there are cases where you can see the limits of precision. The new code (which will be in preview 3 or beta 1) uses 32 pools, for 5 cm precision.
If you use DSF2Text, you can simply use the DIVISIONS command to specify how many pools you want.
WorldEditor’s internal representation is 64-bit floating point, which gives precision better than 1 mm.
In MeshTool 2.0, you can specify how wet orthophotos are handled. There are three possibilities:
- The orthophoto has no alpha-based water. The alpha channel will be ignored.
- The orthophoto has alpha-based water. Draw water under the alpha, but for physics, make the triangles act “solid”.
- The orthophoto has alpha-based water. Draw water under teh alpha, and for physics make the triangles act “wet”.
The reason for 2 and 3 is that the X-Plane physics engine doesn’t look at your alpha channel – wet/dry polygons are decided on a per triangle basis. (The typical work-around is to use the “mask” feature in MeshTool to make some parts of the orthophoto be physics-wet and some physics-solid. This is described in the MeshTool README.)
Whenever possible: don’t use alpha-based water at all. It is certainly easy to set all of your orthophotos to alpha-water + physics-solid, but there are three costs to this:
- You eat a lot of fill rate. X-Plane manages alpha=water by drawing the water underneath the entire orthophoto, then painting over it with the orthophoto. This is fill-rate expensive. If you know there is no alpha, tell MeshTool, so it can avoid creating that “under-layer” of water.
- If the terrain is very mountainous, you may get Z-buffer artifacts from the layering, particularly for thin, spikey mountains (which probably aren’t wet anyway).
- The reflection engine tries to figure out the “surface level” of the water, but it doesn’t understand the alpha channel on top of the water. So all of that water “under” your mountain or hill is going to throw the reflection engine into hysterics.
Limiting the use of water under your orthophotos fixes all three problems.
