• A Bigger Picture

    View of the rails from inside the simulator. Screen is 8 feet wide.


    B i g g e r
     Picture

    Creating a better out-of-window view for Microsoft's Train Simulator

    Elden Slick

    Several flight simulation fans enjoy the hobby of building recreations of aircraft cockpits to provide themselves with an additional amount of immersion and realism with flight simulation. The efforts range from simple, arcade-like booths to full-blown simulators built upon the actual remains of retired aircraft. 

    To date, I am surprised to find little activity of this nature in the train simulation arena. I am convinced there are several efforts under way, and it's mostly a case of the builders not advertising their accomplishments over the net - just yet.

    If all this sounds very new to you, then allow me to share my experiences building a "general purpose cockpit" - an environment capable of supporting a variety of drivable craft, with recent emphasis on locomotive support. The general purpose design results in a cockpit which is not specific to any particular craft, so its resemblance to an actual locomotive interior is severely limited. The situation is made more complicated by the vast variation in the design of locomotive cabs, as their form increasingly follows their function. Nonetheless, its 2-seat side-by-side layout is of approximate width of modern diesel cabs.

    Microsoft's Train Simulator is remarkable for the amount of technical complexity addressed in the first release. However, this first release does not support several features which would make simulation support easier. These deficiencies should not deter the determined builder, and I offer some strategies and technologies used by myself and many others to offer inspiration.

    Several components in a simulator must work together to provide proper stimulation to your senses. Although we cannot affect your middle ear, we will address your remaining senses as accurately as possible (perhaps going overboard at times). This article concentrates on the out-of-window view, since the visual component is the single most effective element in simulation. When driving, you spend most of your time looking out the windshield, so effort spent improving  the forward view yields considerable results.

    Several techniques can be employed to improve your view of the TrainSim world. The various strategies and components are listed in order of expense. Hopefully, one of these solutions will fit your budget.

    A Fresnel Lens

    The Fresnel Lens

    A fresnel lens has unusual properties. It collects light from a point source, and re-directs it in parallel directions. Used "backwards" (capturing the "parallel" rays of the sun, and gathering them to a point source), it is a potent weapon. Used "forwards" (capturing the emitted rays of your monitor), it provides a degree of magnification. This property  is used by some cockpit builders to achieve a larger picture than their monitor can display. The lens must be placed a prescribed distance in front of the monitor. Some fresnel users actually claim a certain "depth" to the image not available on a regular monitor, but this depth should not be confused with 3-D perception. 

    A quicktime animation of a fresnel lens in action can be found at the PBS.org website.

    The design of the lens makes it useful in a variety of applications, but by-products of its properties equally apply in simulators. The magnified image is highly directional, meaning the lens must be positioned precisely in front of the monitor, and your viewing position must likewise be critically arranged along its optical axis. Someone watching over your shoulder (off the optical axis) may not see the image very well at all.

    Nonetheless, it is a low-cost entry to larger-than-average views, and users claim various degrees of satisfaction with the lens in single-seat cockpits.

    Projector Panels

    Overhead Projectors & Projector Panels

    If you took a laptop computer's display apart, you would find it is made of 2 major components: the Liquid Crystal portion, which contains the matrix of liquid crystals (the part that forms the image), and an electro luminescent backlight which illuminates the panel. Separating the matrix from the backlight, you could hold the panel up to a window and see an effect similar to looking through stained glass. A few IBM laptops were designed to actually do this, with the intent of placing the LCD portion on an overhead projector for presentation purposes.

    This arrangement provides a low-cost entry into digital projection, and a few dedicated products are on the market to save your threatened laptop. They have VGA connectors and lie flat on the overhead projector, letting the projector do the job of illuminating the panel and projecting the image.

    I have never seen these in action, but can imagine a few problems which need to be considered. The switching time of some of the more inexpensive panels could cause a "smearing" of the drawn image, similar to what is observed on the more inexpensive laptop computers. Only a fraction of the light produced in an overhead projector actually arrives at the screen, meaning a lot of light is scattered in non-productive directions. It is probably a good idea to deal with any light leakage which could occur around the panel, but not interfere with the cooling path of the projector, itself. In other words, you would want to preserve the darkness of a night mission, without stray light entering your cockpit or landing on your screen.

    Some brave souls have cobbled together the various necessary components to make their own projection systems. Several do-it-yourself efforts have been documented at http://www.diyprojectors.com/. The site provides lots of information for those curious enough to pursue this lower-cost option. You just might be encouraged by the success of others who have pursued this route. Author's note: this site has seemed to go off-line during the writing of this article. The link is provided in the event that they might return soon.

    A Large Format TV / Monitor

    Large Format  TVs & Monitors

    There is little doubt that several large-format televisions are serving double-duty as huge displays for console (X-Box and similar) gamers. Keep in mind that console games operate at a very low resolution compared to computer displays. Some computers (including my laptop) provide an s-video output, which readily connect to properly-equipped monitors. As a step up from s-video, a number of devices exist which will accept computer VGA as an input, and convert the signal to component video out, which is used by HDTV with progressive scan capabilities. Check the specifications of your TV / monitor before connecting a computer, or you risk the possibility of damaging your TV.

    Although the concept of dedicating a display of this size to simulation might seem rather odd, these devices are less expensive than projection systems. I am aware of at least 1 simulator which has 3 large-format TVs arranged to give a panoramic view in a flight simulator. These three large monitors cost less than the price of a single projector of two years ago.

    I wanted a larger image - one capable of being viewed by 2 or more people in the cockpit. The image should be equally bright for all viewers regardless of the seating angle. A projector-based system seemed the most appropriate solution for these requirements.

    Digital Projectors

    Projectors

    "Real" simulators use multiple projectors to generate overlapping wide-field images used in simulation. The effects they produce are stunning, often invoking genuine panic responses in seasoned pilots using them for safety training.

    As mere mortals, such systems are beyond most of our reach, yet projector technology is readily available. An increasing variety of projectors are appearing on the market. They are becoming increasingly specialized, and their prices are steadily dropping. Keep an eye on eBay for possible opportunities. They also turn up as used or refurbished on several "projector specialty" websites.

    They are very versatile devices; used for presentation purposes, deployed in control centers, and becoming more popular in home theaters and screening rooms. They usually have a small internal amplifier and speaker, support a computer-type mouse, and support VGA and s-video inputs. Most are capable of flipping their projected images on both the horizontal and vertical axis to support variations like rear-projection or inverted ceiling mounting.  They are equally comfortable showing video as well as computer input. My projector serves double-duty in the living room as the backbone of a home theater. Everyone who has watched a movie there agrees the experience is "just like going to the movies".

    The most important features I have found include keystone correction, front/rear projection capability, and  video input. HDTV (16:9) support  works excellently with those DVD players which support anamorphic capability. 

    Projectors are characterized by a number of properties, making comparisons fairly easy. In general, the larger the value of the metric, the better. They are becoming increasingly feature-rich. The challenge is to look for the most meaningful features, and save money by not purchasing the rest. Here are the most commonly listed properties.

    • Resolution

    A projector's native resolution refers to the dimensions of the hardware drawing the image, or how many pixels it can display in both dimensions. Almost every projector will accept a higher or lower displayed resolution (for example: a 1024x767 device in the projector will display an  image if your computer's graphics card is set to a higher or lower resolution), but higher resolutions will appear a bit fuzzy. It is very similar to the way a laptop approximates resolutions which are not native to its display.

    At first, a resolution of only 1024 pixels seems a bit skimpy for a screen which might measure over 100 inches (over 3 meters) across, but you can compensate by experimenting with some of the rendering options of TrainSim. The most effective improvement is to "de-jaggify" the railings and the outlines of any model's geometry as seen against the background. This is achieved through a technique called anti-aliasing. Though computationally expensive, this rendering effect will go very far to restore the apparent loss of resolution.

    TrainSim supports full-screen anti-aliasing, but you won't find it in the "options" section of the sim. You have to invoke TrainSim from a MS-DOS shell with a special parameter per this example:

    c:\program files\microsoft games\train simulator\train.exe /fsaa

    ...where "/fsaa" stands for "full screen anti-aliasing".

    Anisotropic filtering is a technique for reducing "noise" from textures by mathematically processing texture information into a more improved appearance.  Once again, from a MS-DOS shell:

    c:\program files\microsoft games\train simulator\train.exe /anisotropic

    ...just might activate this feature. Visit the Microsoft Train Simulator site's technical section for additional information describing how to invoke these functions by creating an icon which will allow you to start these special versions with a double-click. These options will only work if your graphics card supports those functions. Unfortunately, I have had no luck trying to get them to work on my very new, state-of-the-art GeForce4 card.

    However, all is not lost. As mentioned earlier, the projector can handle resolutions other than those of its native display. In other words, even though my projector is a native 1024 x 767 device, its on-board computer allows it to show resolutions both lower (800 x 600)  and higher (1280  x 1024). Fitting a lower resolution seems easy enough, but what about the higher resolution case, where there is just plain more information to "cram" onto the device? A 1-pixel-width line on a 1280-pixel-wide bitmap should have to be something less than 1 pixel's width when displayed on the 1024-pixel-wide device.

    The short answer is: it works very nicely indeed. The projector's computer performs these conversions on-the-fly, with the resulting effect of "smoothing" the overall image. I'm not sure of the exact process, but the effect seems more similar to pixel dithering than full-screen anti-aliasing. The one-pixel-width line (of the above paragraph) is blended with its neighboring pixels to result in a smaller-than-1-pixel appearance. The net result is an apparent increase in resolution of the projected image. All in all, it's a neat solution; the task of "anti-aliasing" is ignored by the graphics card and given to the projector - a decent example of parallel processing.

    If your program does support full-screen anti-aliasing, it pays to match the resolution of the simulation with the native resolution of the projector. In other words, if your projector is a native 1024 x 767 device, then set the display properties in the game to match. If at that setting, you find your graphics card has power to spare, try enabling the more esoteric rendering functions (like specular lighting, dynamic shadows, and increased mathematical precision) to enjoy a higher quality image.

    • Contrast Ratio

    Contrast ratio is a measurement describing the "distance" (ratio of luminance) between the brightest white and darkest black a device can produce. Higher values result in much more pleasing images, sometimes appearing sharper than higher-resolution systems with a lower contrast ratio. Even though standards exist, it seems as though this number should be used as a guide towards selecting a projector, as some projectors seem to "perform" better than others with similar contrast ratios.  

    • Brightness

    Brightness is simply a measure of the illumination capacity of the projection system. It is measured in ANSI Lumens, and bigger numbers result in brighter projected images. Brighter also usually means hotter operation temperatures, more current consumption, and greater expense. These projectors possess expensive bulbs of varying replacement cost and lifespan. Some bulbs cannot be replaced by the end-user, so it pays to visit the manufacturer's web site to gain this important information.

    Display Technology 

    There are two major projector technologies: LCD and DLP. They are rated by the same metrics.

    • LCD

    LCD Projectors have a miniature liquid crystal similar to the display of a laptop computer. They exist as a single panel, or as 3-panel (separate red, green, blue) designs. A lamp takes the place of the electro luminescent backlight. Like laptop displays, I have observed considerable variation in picture quality and performance, so test-view your projector if possible.

    • DLP

    Digital Light Processors are fairly sophisticated devices. They consist of microscopic mirrors attached to equally minute actuators which modulate light brightness by tilting these mirrors towards or away from a light source. A tiny space exists between the mirrors, so the overall image can have a "screen door" effect not seen with LCD systems. This effect can range from not noticeable at all to somewhat "pixely" subject to factors such as viewing distance, quality of input signal and image being displayed. 

    An excellent description of the DLP process can be found in a flash animation at http://www.dlp.com/ .Click the yellow "Launch the Demo" button for an in-depth explanation.

    DLP technology continues to be developed. Look for the new generation of DDR/12 degree DLP, which promises even greater contrast ratio than current units.

    Screens

    A projector and screen work as a system form the total image. A projector screen has dramatic effect on the quality of the projected image, and this area is the currently the weakest in my simulator.

    Two possible arrangements exist: front projection and rear projection. Both are explained in detail.

    • Front Projection

    Front projection refers to the same layout you experience in the typical movie theater. The projector is behind you, and the image occurs on the front of a screen ahead of you. You are situated between the projector and the screen. The prototype version of my simulator is presently a front-projection arrangement, with the current screen a not-too-fabulous bed sheet stapled to an overhead floor joist. It is pretty weak as far as screens go, suffering from contrast and light loss, and a proper replacement is in the future. Nonetheless, operating in the darkness of my basement, the system provides adequate brightness for both daytime and night missions. If your projector is over 1000 lumens bright, and you plan to operate in a dark room, a wall or other surface painted bright white will work very well.

    When the projector is behind you, there is an opportunity to create shadows on the screen which must be addressed. If the projector is not placed properly, you might see the shadow of your head (or other items interfering with the light path) outlined on the screen. The usual remedy involves placing the projector towards the ceiling of the room, but higher placement creates a "keystone" effect on the projected image. Almost every projector can compensate for this problem with the keystone correction feature.    

    • Rear Projection

    Rear projection places the projector behind the screen (facing you), lighting a special type of screen from the rear. To me, the rear projection is by far the sexier arrangement. A properly installed screen can help isolate the noise of the projector, and there are no shadows cast by objects between you and the typical front projection layout. A properly designed rear projection screen will keep brightness consistent to the edges, easily deals with the "stray light" problem and will remove the "hot spot" created by the projector's light source. Make sure your projector can flip the image horizontally when used in a rear-projection arrangement.

    Rear projection screens are also hideously expensive. The one I am researching is priced at about $2,000.00 for an 8 footer with an HDTV aspect ratio. Some creative users are experimenting with alternative materials for rear-projection screens, using white opaque shower curtain material. Unfortunately, I can't find a shower curtain 8 feet tall and 4 feet wide...

    Rear projections require much more room, since you are placing the volume of the projector's beam on the far side of the screen. Some vendors have managed to shorten this distance by folding the light from the projector with mirrors, but these arrangements are very specialized and fairly expensive.

    Front versus rear projection spatial requirements

    Assuming 6 feet (1.8m) between observer and screen, and a screen width of 8 feet (2.43m) in both cases, the rear projection arrangement would require about 15 feet (4.57m, distance "A") overall, while the rear projection setup requires about 28 feet (8.53m, distance "B"), depending on the depth of the cockpit.

    One recurring problem I have observed from other cockpit builders involves insufficient planning for projector placement. Builders will start cockpit construction without actually owning a projector, and make poor assumptions about the distance required to properly fill the screen, which usually results in smaller projected images than intended. The typical projector with the "average" zoom lens requires about 15 feet (about 4.57 meters) of distance to fill a screen to a width of about 8 feet (2.43 meters). Lenses of varying focal length are available for some projectors, but proper planning will save you the expense of replacing the supplied lens. 

    View File Considerations

    My cockpit is a side-by-side design, allowing two people to enjoy the simulation. However, the default viewport in Train Simulator is defined from the driver's position, which is slightly right of center. This offset makes the tracks appear as though they are positioned slightly to the left. I wanted the tracks to be rendered directly down the center of the cockpit, where they would occur in real life. While test-driving, I found the horizon placed too high, forcing my gaze to an uncomfortable upwards position. Also, the increased width of the screen should permit the viewer "see" more of the outside world, since the default view in TrainSim is bound to a smaller viewport (half a cabin as opposed to a full-width cabin). Thanks to the TrainSim designers, these values are available and alterable via text files within the simulator. Instructions for changing these files follow.

    • The .cvf file

    Each locomotive has directives for aligning the outside scenery with the locomotive cabin's windshield. Altering entries in this file allow you to align the scenery with the locomotive's windshield when seen through the cab view. If you are not interested with the cab view, you can reposition this view to your liking.

    Here is a listing showing the first 8 lines of a locomotive's cab view file:  (<trainsim_source>\TRAINS\TRAINSET\<loco_name>\CAB VIEW\<loconame>.cvf). The first "Position / Direction" entries apply to the forward view. I plan NOT to change the left and right views, so I will leave those alone.

    The numeric values following "Position and Direction" effect the X, Y and Z values for their respective variables. I am going to change the "X" (or first value) for each, changing both to zero. Think about a camera placed on a tripod.  Moving along the X axis amounts to sliding the camera left or right. Changing X value of "Position" to zero will place the camera / tripod precisely between the tracks. Changing X value of "Direction" to zero will pan the camera on the tripod so it points straight ahead. Setting the "Y" value to zero pitches the camera to a level position, which effectively moves the horizon downwards a bit on the screen. Retaining the other values keeps the proper height above the tracks, and distance from the nose of the locomotive.

    [email protected]@@@@@@@@@JINX0h0t______

    Tr_CabViewFile (
         CabViewType ( 2 )
         CabViewFile ( GP38Frnt.ace )
         CabViewWindow ( 43 0 597 412 )
         CabViewWindowFile ( AcWndFrn.ace )
         Position ( 0 3.7 6 ) (changed the first value to zero, do not include this comment in your file)
         Direction ( 0 0 0 )  (changed first two values to zero, do not include this comment in your file)

    Unfortunately, the .cvf file has to be altered for each engine you possess, but all .cvf files should be changed similarly. A cut-and-paste (and paste, and paste) session will get you there quickly. Make sure you backup your .cvf files if you decide to revert to the original values.

    • The Camcfg.dat file

    The <trainsim_source>\GLOBAL\Camcfg.dat file determines the parameters for the various "camera" views found within TrainSim. I made a few changes to the Camcfg.dat file to show more of the outside world by increasing the "field of view" (seen as Fov in the listing below). The default value of 60 is roughly the field of view of a human's eyes. Bumping the number from the default 60 to 90 yields a slightly more wide-angle (or fisheye) field of view. This is technically not the correct way to "include" more of the outside view, but it's the only one available to change. You will see more of the outside world, but closer objects will appear slightly further away than they should, just like the way the passenger-side mirror in your car behaves. This also means that objects will get closer more quickly as they approach. The trade-off is acceptable to me, and behaves better than the default settings. You can always trim this number downwards to something more personally acceptable to meet your particular display. 

    The below comments in gray are provided for notation purposes only, and should not be included if you make changes to the files. 

    camera ( CamTypeCab
             CamType ( CamTypeCab CamControlViewSwitch )

            CameraOffset ( -0.51231 4.28496 10.0387 ) (author wonders: why aren't all these values zero?)

            Fov ( 90 ) (this value was 60)
            ZClip ( 0.5 )
            WagonNum ( 0 )
            Description (Cab_Cam)
    )

    Showtime

    The camera file has been altered, the .cvf files are updated, computer, projector and screen are in place and it's time to launch. Since I am interested in rendering ONLY the outside world (because we are modeling what you would see out the windshield), the inside cab views and controls are of little use. Nonetheless, one might want to keep things like the track monitor, and perhaps the HUD displays to keep tabs on the situation. 

    Transparent track monitor directly in front of field of view, similar to a "Heads-Up Display". Keep in mind we're only seeing about 2/3rds total width of the image. The driver is seated in the left seat in this situation.

    Barry Andrews (and others) has cleverly made a transparent version of the track monitor. Properly positioned in front of the driver, the transparent track monitor takes on the appearance of an aircraft Heads-Up Display. Look for a file named trnsprnt.zip on TrainSim.Com. TrainSim's HUD (those little red words which appear in the upper right corner) can give additional information concerning the state of the controls, but I find I can drive without this information. Of course, you can peek at these values when needed.

    An 8 foot image fills the majority of your eye's field of view, amplifying movement to the point of motion-sickness for some. I particularly enjoy slowly releasing the locomotive brake, and watching the sloooooooow movement of the tracks as they disappear "under" the console. Using the external view, you can see train images which would appear full-sized to an observer, depending on the view chosen by the simulator. The occasional overhanging tree-branch becomes menacing. Passing other trains takes on a substantive aspect. For those who venture into other areas; racing, flying and combat take on very realistic proportions. Add a properly configured sound system, and things get pretty interesting.

    We're off to a good start with a proper forward view, but there is more work to complete the "driving" experience. Stay tuned for the next article.

     

    [email protected]


    Article copyright M.Elden Slick, 2002.

    Microsoft and Microsoft Train Simulator are registered trademarks of Microsoft Corporation.

     

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