There are a few changes to 940 regarding airplane lights…I will try to get some permanent documentation on the Wiki, but here’s the basic ideas:
There is a new “type” of light in the OBJ8 format, called a parameterized light. A parameterized light is somewhere between a named light (totally as-is, can’t be modified, simple to use) and a custom light (totally complex, can do anything, requires a lot of work). In a parameterized light, you control just one or two aspects of the light.
Parameterized lights are aimed at airplanes, not scenery, because typically parameterized lights are customizable and slow.* The goal is to give airplane authors some flexibility without having to invent a huge number of named lights.
Consider, for example, landing lights. A landing light could vary based on what switch controls it (we have 16 now), how big it is (many authors have pointed out that one size does not fit all) or how wide it’s view angle should be. (Lights that are inset in a structure might not be easily viewable from the side.) With a parameterized light, we can provide one light definition with 3 parameters instead of a huge matrix of lights.
Generic lights are a new collection of 64 lights that can be used for any purpose, sort of like misc wings, misc bodies, and sliders. The main difference between a landing light and a generic light is that the landing light halo won’t show up on the runway when a misc light is turned on. They are meant to be used for logo lights, inlet lights, etc. A series of new named lights will “listen” to the generic switches.
(Tip: combine ATTR_light_level with generic lights to have a light turn on and your lit texture appear at the same time.)
Finally, there is now a plugin override for the beacons and strobes (and in the systems model there can be up to 4 separate sets of beacons and strobes flashing at different times). With parameterized lights you can make two sets of strobes and use a plugin to control when they flash.
The combination of these three things let an author create an airliner that models all of the various lights and their behaviors.
* Slow needs some qualifications here. There are two code paths for lights, the fast and slow path. The slow path IS pretty fast, just not as fast as the fast path. The fast path is expected to be able to draw at least 10,000 lights in a single frame on low-end hardware, while the slow path is expected to be able to draw at least 500 lights per frame on low-end hardware.
500 lights is a lot for one airplane, especially if you have to place them by hand. And most modern computers will easily do thousands of slow lights.
Basically slow lights are not appropriate for scenery objects in the library that might be placed a huge number of times: OBJs attached to roads (e.g. street lights), OBJs used for buildings, taxiway lights. The are plenty fast for airplanes. In the X-Plane world, slow doesn’t really means slow, just slower than something else.
Two warnings about normal maps:
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Make sure that the RGB color underneath transparent sections does not turn black or white! Some image editing programs (in particular Photoshop) will lose the color beneath a transparent area.
With a normal map, this is very bad – black and white are not legitimate normal map colors, and the result will be bogus normal vectors under the non-shiny part. Normal maps affect more than just specular shiny hilights – the normal map affects all lighting, so having black or white under your transparent (non-shiny) parts is bad news.
To check whether this has happened, I recommend Graphics Converter, which will show you your alpha and RGB channels separately, exactly as they are in the file.
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Make sure your RGB value are normalized. The “length” of the normal (as encoded in RGB) must come out to a distance of 1. This is virtually impossible to do using PhotoShop or an image-oriented program…I suggest you use a real plugin to PhotoShop or Blender to create normal maps that are correctly “normalized”.
It is also very possible that X-Plane’s gamma correction is distorting normal maps, but that’s one for me to fix.
X-Plane 940 now supports normal maps on OBJ models (both scenery and airplane). I’ll get more formal docs up once the rest of my office is moved and unpacked but here’s the details for now:
The normal maps are in “blender” format see here. The alpha channel is optional; if it is present, it serves to modulate the level* of specularity. Opaque means full specularity, transparent means none. You can use this feature to make some parts of an object shiny and some dull on a per-pixel level.
Shininess level is modulated by both ATTR_shiny_rat and the alpha channel, so you need ATTR_shiny_rat 1.0 and an opaque alpha channel (or no alpha channel) to see full specularity.
Normal maps are only available for objects and only appear if pixel shaders are on and per-pixel lighting is enabled.
Normal maps should be PNG format, not DDS – they will not be texture compressed because S3TC compression tends to kill them. (There are some modern formats for normal map compression supported by the newer cards but we don’t use them yet.)
* Specular level: most serious 3-d programs let you control both the specular exponent, which controls how “tight” the specular hilights are, and the specular level, which controls how bright they are. X-Plane only lets you control specular level; if specular hilights exist, they are always as the maximum exponent for the sharpest specular hilights.
I have received several requests for a transparent runway with a physical surface type. That request is just strange enough that we need to look back and ask, “how did we get here?”
High Level and Low Level Modeling
The “new” airport system, implemented in X-Plane 850 (with a new apt.dat spec to go with it) is based on a set of lower level drawing primitives, all of which are available via DSF. In other words, if Sergio and I can create an effect to implement the apt.dat spec, you can make this effect directly with your own art assets using a DSF overlay. This relieves pressure on the apt.dat spec to become a kitchen sink of tiny details.
The goal of apt.dat is to make a visually pleasing general rendering of airport data. DSF overlays provide a modeling facility.
Little Tricks
It turns out there are two things the apt.dat file “does” with the rendering engine that you can’t do in an overlay DSF:
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The apt.dat file registers runways in the airport dialog box (for starting flights, positioning the airplane, etc.).
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When the apt.dat reader places OBJs to form approach lights, it can offset their “timing base”, which is why the rabbit flashes in sequence.
(If you were to place a sequence of approach lights with rabbits in an overlay, every single light would flash at the same time because the DSF overlay format does not have a way to adjust the object’s internal timing parameter.)
The solution: the transparent runway. The idea of the transparent runway is to create with the apt.dat file the two aspects of a runway that you can’t build with a DSF overlay: the approach lights and the entry in the global airport dialog box. Transparent runways leave the drawing and surface up to you.
My thinking at the time was that the actual runway visuals and physics would be implemented together via either draped polygons or a hard OBJ.
Orthophotos and Bumps
So why do authors want a transparent but hard runway? The answer is orthophotos. With paged orthophotos, it is now possible to simply put down orthophotos for the entire airport surface area (whether as overlays or a base mesh) at some high resolution (our runways are 10 cm per pixel – I’m not sure if the whole airport area can be done at that resolution) and not have any special overlays for the runways. The transparent + hard runway would change the surface type.
I’m not sure if this is a good idea, but I’m pretty sure that this feature belongs in overlay DSFs and not the apt.dat file.
- Such a technique (varying hard surfaces independent of a larger image) is useful for more than just airports (and certainly more than just runways).
- The technique is unnecessary unless a DSF overlay is in use.
- Unlike nearly all of the rest of the apt.dat file, such an abstraction (invisible but bumpy) is much more a modeling technique and less a description of a real world runway.
I’m not sure we would even want the runway outline to be the source of hard data. If there are significant paved areas outside the runway then a few larger hard surface polygons might be more useful.
I’m not sure if these will make it into X-Plane 9.30 (we’re trying to close down features, but it doesn’t do much good to hold off features that help people make airplanes) but…while I was in Italy I created a few more manipulator types.
The set of manipulators let you change the value of a dataref directly with a mouse-click – the various flavors control how the dataref is changed.
These manipulators are the natural corollary to the command manipulator, which runs a command on a click.
Why have both? Commands are good, but they don’t cover 100% of sim functionality (just like datarefs don’t cover 100% of sim functionality). By having both, it will be possible to control switches and buttons that are best accessed by a dataref change.
For the basics on commands vs. datarefs, see
here.
The generic instruments already write to both commands (via the trigger instrument) and datarefs (via the rotary instrument) – these new manipulators provide the same functionality for 3-d cockpits.
It seemed like opposite-day at Laminar Research…Austin saying that an error shouldn’t quit the sim and me saying the error was never okay, ever. Well, I relented: with X-Plane 930 beta 8, if your scenery pack is missing objects, you can still fly. Instead you get a single error message like this:
That is the “non-fatal” error dialog box – you will see it only once for each scenery pack with a problem for each time you run the sim. It means that at least one thing is wrong with your scenery pack, but you need to look at Log.txt to see what’s wrong. For example, you might see this in the Log.txt file:
Failed to find resource 'KSBD_example.obj' at 'Custom
Scenery/KSBD Demo Area/KSBD_example.obj'
Failed to find resource 'KSBD_example.obj' at 'Custom
Scenery/KSBD Demo Area/custom objects/KSBD_example.obj'
Failed to find resource 'KSBD_example.obj' at
'Resources/objects/KSBD_example.obj'
Failed to find resource 'KSBD_example.obj'
at 'Resources/KSBD_example.obj'
***Error with scenery file "Custom Scenery/KSBD
Demo Area/Earth nav data/+30-120/+34-118.dsf"
(/Volumes/RAID/code/design/HLutils/Files/io_dsf.cpp: 503.)
Unable to locate object: KSBD_example.obj
In this case, X-Plane couldn’t find the object KSBD_example.obj – the sim is also listing all of the places it looked. Note that only the first location is a good location – the other 3 are legacy search paths that date all the way back to version 6. It is likely that in the next major version we will trim down our search paths significantly.
A few comments on this whole situation:
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Authors, do not ignore error messages like the dialog box above – every one of them indicates a condition serious enough that we think you should fix it. Non-fatal errors like these may crash future versions of the sim, or your content may simply stop working.
If you file a bug against a future version of the sim saying your scenery pack used to work and is now broken, and we find that the old scenery pack had errors, we’re not going to fix the bug – we’re going to laugh maniacally and dance around you in a circle while singing “told you so”.
Okay – we’re very unlikely to do that – but if you have errors in your scenery pack, you’re doing something wrong and you need to fix it – treatment of illegal data is not stable between versions of the sim!!
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I was never very sympathetic to this whole bug report because X-Plane has never accepted a DSF with missing objects – this has been a fatal* error since X-Plane 8.0 when DSF was introduced. So I simply don’t understand why there are any scenery packs floating around with objects missing. Why would you place an object if you don’t want to see it? The whole issue strikes me as a total failure to check quality by authors, since even running your pack once would reveal this kind of problem every time!
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The motivation to make missing objects illegal comes from version 7 and ENVs. When looking at ENV scenery, I found that a large number of ENV scenery packs were missing at least some of their objects (an error that was silently ignored in ENV). It seemed like we were hiding an error and the result was authors not noticing simple mistakes that might “lose” an object (e.g. renaming an OBJ file).
Hence the “harsh” policy for DSFs – it was in response to a real problem with existing scenery!
- You don’t need to have missing objects just because you use library objects from another scenery pack (that might not be around). Use the EXPORT_BACKUP command in your library and a single blank OBJ as a place-holder for the objects you want from a library that might be missing. OpenSceneryX provides a stub library that authors can include so that their scenery will load without errors even if the OpenSceneryX library is not installed.
Anyway, Austin was right to make the error non-fatal. Besides being a little bit nicer for users who don’t know (or care) why their pack is gone) it lets authors get a list of all missing objects with only one run of the program.
* Fatal? In computer terms, a fatal error is one that makes the program quit, e.g. the error is fatal because it kills the program.
With X-Plane 930 beta 8, we finally integrated the latest version of Max’s Cessna 172 SP. Grab the new beta and try it – he’s added a number of new features that demonstrate some of the newer X-Plane 9 airplane features.
- Real 3-d lighting in the 3-d cockpit. Note how the map light tends to illuminate only some of the cockpit as it fades out.
- 2-d back-lighting on all of the major steam gauges.
- A bunch of parts can now be dragged in 3-d, including the door handles. This is done via manipulators.
- Walls! In 3-d cockpit viewer mode you won’t be able to leave the airplane until you actually open the doors. The cockpit viewpoint is constrained.
- The model has the glass parts separated out for correct shadowing, and the glass works correctly from all viewpoints.
- Panel uses cockpit regions for accurate lighting.
The cirrus jet has been similarly updated. I plan to use the Cessna for a series of tutorials showing how to use these recent X-Plane features.
I have said this before, but now it’s finally true: new file specifications are subject to change in the middle of beta!
In particular ATTR_light_level has changed slightly from beta 7 to beta 8. If you are using this feature in your objects, you will need to update your objects.
A new ac3d beta will be posted later today that supports the updated syntax.
You can read about the syntax here.
Propsman caught something:
…is modifying the value of a batch of ATTR_light_level tris comparable [performance-wise] with toggling the state of a backlit generic instrument? Instinct tells me that you must have the latter more streamlined than the former, but maybe not?
He is right: in the current implementation, ATTR_light_level is probably a bit more expensive than using generic instruments. This may not be true in the future though.
- The generic instrument code is pretty tight.
- Right now ATTR_light_level sometimes has to adjust shaders, which can be expensive.
- In the future, ATTR_light_level has the potential to be very heavily optimized, while the generic instrument code will always be CPU based.
But to put it in perspective, all instrument drawing is slow compared to scenery drawing – in the scenery world we draw 50,000 triangles of identical OpenGL state in a row, and modern cards do that very, very well. In the panel, we have to put in a lot of CPU time to figure out how to draw each quad or tri-strip. Fortunately you probably don’t have 50,000 individually programmed flashing lights in your panel. Heck – there’s “only” 3608 datarefs published by the sim.
Perhaps other questions are important when picking ATTR_light_level vs. panel texture:
- Which is more useful: to be able to have several variant images and variant images that are not “lights” (this is only possible by generics) or the ability to vary the light level gradually and not just have on or off (this is only possible with ATTR_light_level)?
- Which is simpler to author given the rest of the panel?
In other words, it’s all pretty “slow”, but fortunately “slow” isn’t that slow. If your light has to blink, you may want to pick what looks best and is straightforward to author.
In my previous posts I have tried to explain the difference between commands and datarefs, and when you might use each. To review:
- A dataref represents information. You can always read it, and you might be able to change it.
- A command represents an action. You can always invoke the action, but you can’t tell if it worked without looking at a dataref.
So…why is there so much overlap and duplication?
Dataref Vs. Dataref
There is duplication in the datarefs because we don’t delete old datarefs when we add newer, improved ones. The old datarefs stay in place to keep old plugins working. Here are a few reasons why we’ve added new datarefs:
- The
cockpit2/ and flightmodel2/ sections were added as a new, simpler, easier to use interface for authors in version 9. (Read more here and here and here.)
- In some cases, the old dataref was a bit-field while the new one is a simple integer. While plugins can use bitfields, modelers cannot animate using bit fields.
- In some cases, the old dataref did not represent a clean view of the data. Some old datarefs exposed X-Plane internal structures that are not appropriate for long-term use.
To see this in action, let’s look at the autopilot. How many ways are there to set the autopilot mode?
sim/cockpit/autopilot/heading_mode. This is the original heading mode, and it is marked deprecated, because it exposes a bunch of internal X-Plane autopilot values.sim/cockpit/autopilot/autopilot_state. This is the ideal autopilot dataref for plugins. It provides all functions, but since it is a bit-field it is not useful for authors.sim/cockpit2/autopilot/heading_mode. This is a clone of the original heading_mode into the cockpit2 domain. Honestly I am not sure how it got there – I know it was me who put it there, but it sure is a dumb idea; the original dataref is deprecated, so it was stupid of me to duplicate it!sim/cockpit2/autopilot/heading_state. This is coming in 930 and provides a heading-state enum set appropriate for authors…basically an enum that matches the two heading bits of the autopilot_state dataref that programmers were using.
How do you sort through this? Three rules of thumb:
- Try to use
sim/cockpit2 and sim/flightmodel2 when possible.
- More recent datarefs are usually better.
- Use the most useful dataref you can find.
Commands Vs. Commands
Sometimes there is some duplication of commands, e.g.
sim/engines/carb_heat_on Carb heat on.
sim/engines/carb_heat_off Carb heat off.
sim/engines/carb_heat_toggle Carb heat toggle.
Here it’s a lot more obvious why there are multiple commands: they affect the carb heat in multiple ways. Typically this is done because commands are mapped to joysticks and other USB hardware; some hardware generates a button press when a command is toggled, but some hardware generates two commands, one for the off and one for the on position.
The rule of thumb is: use the command that gives you the action you want.
Commands Vs. Datarefs
Very often there will be a command and a writable dataref. Typically we need them both:
- The command is needed to let users set up their joystick and keyboard.
- The dataref predates version 9 – writing it was the only way to invoke an action.
Newer datarefs are more likely to be read-only, as we put new “changing the sim” functionality into commands. To go back to our autopilot example, we have on command: sim/autopilot/heading that lets us arm heading mode. This command is probably preferable to any of the datarefs for changing the autopilot state.
My
previous post discusses writing to a dataref. vs. actuating a command in more detail.
