Version 3.1.6
Peter Lürkens
Peter . luerkens ( @ t – online . de )
The automatic thermal scenery generator program is a software tool which allows to scatter large areas with thermal lift to enable thermal soaring within Microsoftâ Flightsimulator 2004. Using the program is as simple as pressing a button. It requires only very few input parameters to generate hundreds of thermal clouds, scattered over the landscape.
Unlike other tools it produces a scenery file, which, by itself has a highly dynamic behaviour, just like the thermal lift at real soaring.
It requires SCASM 2.96 of Manfred Moldenhauer which is not included in this package. The program was tested on Windows XP.
In the twentieth of the 20th
century soaring, or better gliding, was very popular among the aviation
enthusiast of the
While it was clear that wind blowing against the slope will get an upward direction which allows the gliders to stay aloft for while, it was soon discovered, that it was possible to climb even higher then the elevation of the starting point, soaring in the ridge lift was born !
Competitions were organised, mainly on time staying aloft, but later also on the longest distances. The pilots began to cruise along the ridges. However eventually even the longest has its termination, an he had to return. Sometimes they managed to gain enough altitude to jump over to the next ridge, and, very sometimes, longer flights of remarkable 100 km have been shown. However the Rhön-Indians were increasingly discouraged and it was already commonly expected, that, latest after returning to powered flying, the phenomenon would disappear again.
Though it was known, that large birds, by some mysterious capability, could manage to stay aloft hours and hours, virtually without any flap of their wings, nobody got the right idea, when sometimes gliders extended their flights much longer than expected, even when the wind speed was very low. Instead this was reported as “week-wind flights”.
Then, during a thunderstorm, a pilot named Max Kegel was caught by a cumulonimbus cloud and was whirled upwards approximately 2500 m, which gifted him a cross country flight of 50 km, independent from any ridges. The gliding people immediately realised two things: There was a much more powerful and versatile engine for the gliders they ever thought, and it appears to be possible to cover long distances in any direction. Thunderstorm flying became quite popular until it turned out how dangerous this is. Today no responsible pilot would enter freely a thunderstorm anymore.
But now it was clear that local columns of vertical air movement, thermals, would allow even cross country flights of unanticipated distance. A number of technical inventions still had to be done. The most important of it, the variometer, happened to be invented by Max Kronfeld. This little instrument shows the rate of climb immediately and allows the pilot to decide on being in a lift area, worth to stay or not. Max made a big mystery out of his invention, since it provided him with a significant advantage over his competitors.
The freedom of flying had arrived now at the soaring community too, the thread of having touched the fundamental limits was removed.
But, what is really the motor of the
thermal lift? Of course, the sun, which warms the air, that becomes lighter
then the cold air and starts to climb, most people would say. However that is
only part of the story. While the air is raising into
regions of lower pressure, physical law of adiabatic expansion says to us, that
the air will expand, and thus become colder. Eventually it is not hotter
anymore than its environment. Then, latest, the movement of the air will cease.
Even a high initial temperature difference would produce thermal columns of
only two or three hundred meters. In
But when the temperature of the atmospheric layers is becoming colder and colder when you go to higher altitudes, and this temperature decreases faster with increasing altitude then the temperature of the raising air in a thermal lift, then the temperature of the raising air remains higher then the temperature of the environment, perhaps for thousands of meters. Then we will have strong thermal activity. To set the upstream in motion a weak trigger is sufficient, such as a hot spot or even some irregularity in the landscape. Once it has started the draught catches even still air which joins and amplifies the thermal column.
Actually the thermal stratification of the atmosphere is the most important parameters for the development of thermal lift. Is the rate of temperature decrease less then 0.7°C/100m, a stable stratification is given which does not produce any useful thermals. Is the rate higher than 1.0° C/100m strong thermal activity can be expected. The origin of the stratification again is the sun which heats the ground, that serves as an energy storage until by some large weather system cold air pours in which is quickly heated from beneath by ground contact. So the air-mass is increasingly destabilised.
Meanwhile the way of thermal soaring has developed to a kind of the standard mode of soaring, of course other kind of lift are also quite important, in particular ridge lift or ridge thermals in the mountains, but also wave lift which allows to achieve altitudes with a glider plane, a 747 cannot live within (14.000 m MSL is the record I think).
Long distance flying has reached a performance level which only 10 years ago would have been considered to be impossible, the world record has been set in 2002 to more than 3000 km - in one day !
Despite the question if further improvement is still possible (I personally believe), thermal soaring is different everyday, because the weather is, because you are. Every flight the question is asked new: Are you better ? That is the real thrill of soaring, improving your own performance, accepting the challenge to increase your personal longest flight distance, to increase your personal average speed, or just to stay aloft when nobody else does.
The beginning of this story is a bit bad. Though MSFS has a glider out-of-the box since long, soaring apparently was not on the spec-list of the designers of the software package. The glider flightmodel is rather limited (slipping is nearly not possible), its instruments are not really suitable for soaring, and finally, soaring is only possible in a very few limited areas where the lift is at 4 defined positions, constantly, the whole day. As you can imagine after reading above, there is no thrill in soaring with MSFS.
While the weather model of flight simulator consists mainly of horizontal wind, some visual effects of clouds and a bit of temperature and pressure to deflect the aircraft instruments, the inner relations of the atmosphere and their meaning for the development of weather effects are not covered. Maybe its really to difficult to do this in a PC based hardware environment, compared to a Cray supercomputer.
Luckily, the MS designers have spent a small command to create an effect on the aircraft which resembles somehow thermal lift when the aircraft is in, and since a few years this is even documented. This offers scenery designers to create their own thermal area, and meanwhile there are a number of public-domain tools out which allow to place cells of thermal lift neatly throughout the whole landscape.
Once you are in a cell it will carry you upward, to the altitude the scenery designer has determined. As with the MS sceneries, the lift remains all the day at a fixed and predetermined place.
After reading above you know, that challenging thermal soaring is dealing with the unknown and unexpected. For this purpose the conventional approach is too static by far. CUMULUS! therefore produces thermals, which have a life cycle which is different for every thermal cell. So a scenery file with CUMULUS! thermals is highly dynamical. The thermal lift begins first when a cloud is not yet visible. Then after a while a small cloud appears, later it changes to a big cloud. Eventually the lift deceases, while the cloud remains for while. When approaching to a thermal cloud You will never know if it is still active or not. Every cell may have several such life cycles during one day.
The CUMULUS! thermals also imitate the typical profile of a thermal column which is normally surrounded by turbulence and sinking air. Also the region of lift does not extend down to ground, but a bit into the cloud. This can carry you well into the cloud, though not allowed, where it becomes turbulent again. Short above the ground (<150 m) there is only turbulence but no lift anymore.
The scenery produces varying thermals starting at 12.00 local time and ending at 19.00 local time. In the beginning and at the end only a few clouds appear, while during mid afternoon all clouds and thermals are developing. However the amount of lift is fully controlled by Flight Simulator. It changes over the day. Maximum is at 12.00 with 6 m/s, and it decreases to zero at 18.00. These figures indicate the movement of the air not of the aircraft. Depending on the performance and flight attitude (e.g. steeply banked circles vs. flat) the real climb rate is appr. 0.7-1 m/s less. This means useful thermals can be found 17.00 latest, which is unfortunately not very realistic.
Creating a CUMULUS! thermal scenery requires only very few parameters, normally the centre of the area, the shape, the extension or range, the average distance between the thermals and the cloud base altitude. After that a BGL-file is produced, which can be copied into some active scenery folder of the Flight Simulator BGL-Database. An description of the individual parameters is given below in detail. A “.CMS”-parameter file is set up with these parameters and send to the standard input of CUMULUS316.EXE or supplied as the parameter for the batch file CUMULUS!.BAT. In this case the name of the .BGL-File must match the name of the .CMS-file.
Since the last public release 3.1.3 full temporal control of appearance and disappearance of thermal lift and associated clouds in point-list mode was introduced. See the description of the point-list mode below. A side effect is, that input files of the P-mode for release 3.1.3 and before are no longer compatible and have to be re-edited by adding the extra parameter of the beginning and ending hour.
Different from previous releases the delay between thermal activity and cloud appearance is now dependent on the altitude and, in point-list mode, the vertical scale parameter.
Internal changes have now removed the limitations of the point list length, which was formerly limited to 1000 entries. Still the total memory addressable by the program is limited to appr. 67 Mbyte, which can impose restrictions on processing bitmap-defined thermal distributions.
There is a new sample .BAT-file, that creates CUMULUS!-BGL’s, creates automatically suitable scenery folders, and copies the BGL’s automatically thereto in most user environments.
There is also a new option that produces only clouds, without associated thermals, in order to support other external thermal generator programs, such as CCS2004 of Eric Carden, that produce realistic lift conditions, but are not able to produce the associated thermal clouds in real-time.
As of this release, support of Flight Simulator 2002 is no longer included. Probably it will continue to work with older version, but this may be the case or not.
Please note, that no comments or extra white spaces are allowed in parameter file. The comments here are given only for explanation and must not appear in the parameter file.
In circular mode the thermal scenery area is a circle around the centre. The distribution of thermals is uniform and isotropic, while the position of an individual cell is randomised. So you can produce quickly a newly scattered thermal area simply re-executing the program. The parameter file (N50E006.cms) should look like:
Sample file (NE50E006c.cms):
N50E006c : Name of BGL-File
50 30 00 6 30 00 : Center of thermal area in N/E coordinates
(+/-nn° dd’ ss” +/-eee dd’ ss”)
C : Mode qualifier (C), must be first character on the line
100 : Radius in km
5 : typical distance between thermals cells (km)
1700 200 : cloud base altitude, variation (m MSL)
In rectangular mode the thermal area has the shape of an rectangle which makes it easier to tile some larger areas. The extension in any direction is given in km. Thermal distribution is uniform and isotropic.
Sample file (NE50E006r.cms):
N50E006r : Name of BGL-File
50 00 00 6 00 00 : Center of thermal area in N/E coordinates
(+/-nn° dd’ ss” +/-eee dd’ ss”)
R : Mode qualifier (R) , must be first character on the line
100 100 : range in N/S and E/W direction, width is km x km
5 : typical distance between thermals cells (km)
1700 200 : cloud base altitude, variation (m MSL)
In degree rectangular mode the thermal area has the shape of an rectangle, too, but the extension is given in degrees. This makes it easier to make an exact fitting to degree-tiles. The distribution of thermals is uniform but non-isotropic, i.e. the density in N/S direction is less than in E/W direction, the more the greater the distance from the equator is (going to be fixed in later release).
Sample file (NE50E006d.cms):
N50E006d : Name of BGL-File
50 30 00 6 30 00 : Center of thermal area in N/E coordinates
(+/-nn° dd’ ss” +/-eee dd’ ss”)
D : Mode qualifier (D) , must be first character on the line
0.5 0.5 : range in N/S and E/W direction, width is deg x deg
5 : typical distance between thermals cells
1700 200 : cloud base altitude, variation (m MSL)
B-mode is similar to Degree/Rectangular mode, the thermal area has the shape of an rectangle which is defined by the centre and its lateral extension. In addition an RGB-bitmap is mapped on the area which defines the local density of thermals. A black area has a maximum thermal density while white area has no thermals at all. Grey codes specify densities in between. The probability, that at a given place a thermal will appear is
(1-(R+G+B)/3)/average(all RGB’s)
i.e. the more black an area is, the more likely a thermal will be present there. This allows to paint complex areas with active and inactive thermal zones. This is in particular useful in mountain regions, where thermals appear most frequently above the mountains and rarely over the valleys. The bitmap is always mapped to the defined area, regardless of its aspect ratio or dimensions. A useful technique is to scan some map of the deried region and open the image in a layer enabled photo editor such as Paintshop Pro, Photoshop or “The Gimp”. You should use some stretching tool to tweak the map image that the degree net on it maps to a rectangular shape, because the thermal bitmap will be mapped to an orthogonal degree section in longitude and latitude.
After filling the layer that will contain the thermal density information with light grey (to have at least a few thermals everywhere), paint the highly active regions dark or black. A white spot will never have a thermal, while a black spot attracts some amount of the thermals on it, but will never have all the thermals (unless everything else is white). Then this layer is exported as an RGB-Bitmap. Eventually set the limits in the .CMS-File the same as the limits of your map and the job is done.
Sample file (NE50E006b.cms):
N50E006b : Name of BGL-File
50 30 00 6 30 00 : Center of thermal area in N/E coordinates
(+/-nn° dd’ ss” +/-eee dd’ ss”)
B : Mode qualifier (B), must be first character on the line
N50E006.bmp : name of file with density bitmap (24 bit, max 1024x1024)
0.5 0.5 : range in N/S and E/W direction, width is 0.5°x0.5°
5 : typical distance between thermals cells (5 km)
1700 200 : cloud base altitude, variation
The point list mode allows specifying a list of co-ordinates which indicate the exact position and altitude of a thermal cell. Other parameters define the aspect ratio, the timing and if the thermal is a blue thermal or a cloud is visible. Some properties can be randomised as well.
CUMULUS! Program.
Sample file
(NE50E006p.cms):
N50E006p : Name of BGL-File
50 30 00 6 30 00 : Center of thermal area
: (+/-nn° dd’ ss” +/-eee dd’ ss”)
P : Mode qualifier (P)
50 23 22 6 31 40 1700 2.5 1.5 15 0 17 25 -1 0 : blue, parameters see below
50 24 22 6 32 45 1650 1.5 0.7 22 1 23 12 12 13 :
cloud, start at
ends
at
50 25 22 6 29 55 1710 -1 -1 45 -0.5 -1 -1 -1 0 : 50 % probability cloud; aspect
and timing random
.
This format gives the most control over the thermal cloud, however it offers also options for automatic randomising. The parameters in the point-line are as follows:
50 23 22 6 31 40 1700 2.5 1.5 15 0 17 25 -1 0
+/-nn° dd’ ss” +/-eee dd’ ss” ceil hs vs rot cv beg end StartHr EndHr
Parameter description:
+/-nn° dd’ ss” +/-eee dd’ ss” : position of the thermal cell (s.a.)
ceil : ceiling of the thermal cell in m MSL
hs : horizontal scale (should be 1.0-3.0; -1: random)
vs : vertical scale (should be 0.5-1.5; -1 : random)
rot : rotation in degrees
cv : cloud visibility
(0: blue, 1: cloud, 0…-0.99 probability, -1 cloud only, in cloud only mode, the timing is exactly as in the p-mode list)
beg : minute of start (-1: random)
end : minute of end (-1: random)
StartHr : hour of thermal appearance ( -1 produces random
from 12:00-19:00 hrs)
EndHr : hour of disappearance, neglected when StartHr = -1
Remark: In normal mode, the timing refers to the beginning and ending of the thermal lift, while cloud appearance is delayed, depending on ceiling. In cloud-only mode, the timing refers exactly to the appearance and disappearance of clouds.
Note: No parameter files must not have any comments nor extra white spaces, nor empty lines. These are included here only for documentation purpose!
The scenery creation process can be managed by a kind of a make file (e.g. CUMULUS!.BAT). Assuming you have created a subdirectory accepting all the thermal sceneries in the Addon Scenery folder ( say “…\Flight Simulator 9\Addon Scenery\CUMULUS!\scenery” and the associated texture directory) a simple make-file may look as follows:
CUMULUS316 <
%1.cms
Copy %1.bgl
“C:\Program Files\Microsoft Games\Flight Simulator 9\Addon Scenery\CUMULUS!\scenery”
Copy cld2.bmp
“C:\Program Files\Microsoft Games\ Flight Simulator 9\Addon Scenery\CUMULUS!\texture”
Copy cld6.bmp “C:\Program
Files\Microsoft Games\ Flight Simulator 9\Addon Scenery\CUMULUS!\texture”
For those who are not familiar with command line programs and .BAT-files, the %1 parameter is substituted at run-time with the first command line parameter. The extension “.cms” is added automatically in the .BAT-file.
Don’t forget the quotation marks around the path description, incase there are any blanks contained in the path name. The name of the .BGL-file must be the same as the .CMS-file then. After that start a command window, change to the installation folder of cumulus and type “CUMULUS! N50E006”. If the CUMULUS!-directory already belongs to your scenery library, just shut down Flight Simulator and restart. The new thermal scenery is automatically added to your environment. If the thermal scenery folder does not yet belong to your scenery library, change to the scenery library management screen, activate your thermal scenery folder (e.g. “Addon Scenery\CUMULUS!”), and restart Flight Simulator. If you are in the thermal area and it’s between 12.00 and 19.00 you should see the new thermal clouds. If you add more thermal scenery to the same folder, or change the thermal scenery, just restart Flight Simulator.
The distribution package contains already a more sophisticated .BAT-file that usually works in standard environments without modifications. It starts the BGL creation, creates the above mentioned scenery folders, if needed, and copies the produced BGL-files thereto.
Place yourself on an airfield in the region. Choose a glider plane. I propose to use the ASTIR CS of Max Roodveldt, which has a compensated vario. Set clock to 15.00 (not make it too difficult for the beginning). Switch off all Flight Simulator weather clouds. Slew yourself (yes, yes, ...) to 500 m AGL and watch out for clouds. Normally they should have thermal lift, if you are not too late and they have already stopped. When you cruise, be aware that you may enter a lift, even when the cloud is not yet visible.
To make it more interesting make Flight Simulator weather with cumulus (3/8 scattered), a little bit of wind and gentle turbulence. Unfortunately CUMULUS! clouds can still be distinguished easily from FS clouds, so finding the thermals is quite easy.
Now start with soaring and watch the gradual loss of sight when you come close to the base of the thermal clouds.
Create a directory, copy the file CUMULUS316.EXE, CONFIG.TPL, cld2.bmp, cld6.bmp and CUMULUS!.BAT into that directory. Get a copy of Manfred Moldenhauers SCASM 2.96. Copy SCASM.EXE into the program directory as well.
If you have a non-standard installation, of if you don’t want the thermal scenery reside in the folder …\Addon Scenery\CUMULUS!. Modify the path to your Microsoftâ Flight Simulator installation and to the desired scenery folder in the file CUMULUS!.BAT. In standard installations, this should not be necessary.
Since there is apparently no way to control the rate of thermal lift from a BGL-file, thermal lift
only depends on Flight Simulator control. So the rate of lift is
unrealistic (too much during
I did not manage to make the clouds and thermals moving along with the wind. They are at fixed locations. Its still realistic, if the wind is no too strong.
It seems that the internal cloud system of Flight Simulator has some priority over visual scenery objects (makes sense, if you consider everything else below the cloud layer). Sometimes Flight Simulator clouds shine through the thermal clouds.
Now and then it happens that a thermal cloud completely disappears for a second or so, in particular, when you are close up. Maybe its an ATI graphic card error. Spent some time to check it out but could not find a rule (and so no BGL-bug).
When thermal cells are overlapping a part of the turbulence area of one cell may coincide with the lift area of another cell. This leads to the effect that sometimes the turbulence effect remains, sometimes the thermal lift. MS states that this behaviour depends on the sequence of the processing of the graphic objects in the BGL database, which cannot be determined beforehand. The result is a thermal which is unstable and difficult to center. However this happens in real life too …
The author acknowledges the great work that has been done by a large number of persons in the FS community. In particular I would like to mention Manfred Moldenhauer, for creating SCASM, the invaluable tool for the scenery designers, Roland Stuck for designing the beautiful ASW20BL and Max Roodveldt for the essential glider instruments, Wolfgang Piper for a broad range of beautiful vintage and contemporary glider planes, Eric Carden for his great thermal generator program CCS2004, an the complete SOAR community for spending their time during beta testing and producing helpful suggestions for improvements.
The use of this software is on risk of the user. The author gives no warranty for the functionality and the absence of harmful interference with other software or hardware, and is not liable for any damage produced by the software.
The software and its products may be used freely for personal use only.
The products of the software may be distributed freely, provided that there is no charge of any kind asked for the products of the software.
If products of the software are distributed, the author of this software is not liable for the distributed products.
This software and its products may not be bundled with any commercial product without a written consent of the author.
It is not allowed to re-engineer the program code.
The terms of this license may be changed by the author at anytime.
The software may not be used if the terms of this license are not accepted by the user.
Microsoftâ is a trademark of the Microsoft Corporation. Flight Simulator might be a trademark of the Microsoft Corporation.
The component CUMULUS316.EXE of this software package was produced with the Free Pascal Compiler (see http://www.freepascal.org/).
The program is designed for use with Manfred Moldenhauers SCASM scenery assembler, which is not included in this package, as there is no license for free distribution.
For those who are interested in virtual soaring, a very active community is found at SOAR, an internet location, dedicated to the development and proliferation of soaring in flight simulation.
If you are interested in real world soaring, visit FTHA (in german).
Copyright March 2006, Peter Lürkens