U.S. Pat. No. 7,269,539

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the various embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention.

Illustrative Operating Environment

FIG. 1illustrates an example of a suitable general purpose computing system environment100on which dynamic weather may be simulated. The computing system environment100is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment100be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment100.

The invention is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well known computing systems, environments, and/or configurations that may be suitable for use with the invention include, but are not limited to, personal computers; server computers; portable and hand-held devices such as personal digital assistants (PDAs), tablet PCs or laptop PCs; multiprocessor systems; microprocessor-based systems; set top boxes; programmable consumer electronics; network PCs; minicomputers; mainframe computers; distributed computing environments that include any of the above systems or devices; and the like.

The invention may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

With reference toFIG. 1, an illustrative system for implementing the invention includes a general purpose computing device in the form of a computer110. Components of computer110may include, but are not limited to, a processing unit120, a system memory130, and a system bus121that couples various system components including the system memory to the processing unit120. The system bus121may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, Advanced Graphics Port (AGP) bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus.

Computer110typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer110and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by computer110. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer readable media.

The system memory130includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)131and random access memory (RAM)132. A basic input/output system133(BIOS), containing the basic routines that help to transfer information between elements within computer110, such as during start-up, is typically stored in ROM131. RAM132typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit120. By way of example, and not limitation,FIG. 1illustrates operating system134, application programs135, other program modules136, and program data137.

The computer110may also include other removable/non-removable, volatile/nonvolatile computer storage media. By way of example only,FIG. 1illustrates a hard disk drive141that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive151that reads from or writes to a removable, nonvolatile magnetic disk152, and an optical disk drive155that reads from or writes to a removable, nonvolatile optical disk156such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive141is typically connected to the system bus121through an non-removable memory interface such as interface140, and magnetic disk drive151and optical disk drive155are typically connected to the system bus121by a removable memory interface, such as interface150.

The drives and their associated computer storage media discussed above and illustrated inFIG. 1, provide storage of computer readable instructions, data structures, program modules and other data for the computer110. InFIG. 1, for example, hard disk drive141is illustrated as storing operating system144, application programs145, other program modules146, and program data147. Note that these components can either be the same as or different from operating system134, application programs135, other program modules136, and program data137. Operating system144, application programs145, other program modules146, and program data147are given different numbers here to illustrate that, at a minimum, they are different copies. A user may enter commands and information into the computer110through input devices such as a keyboard162and pointing device161, commonly referred to as a mouse, trackball or touch pad. Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit120through a user input interface160that is coupled to the system bus, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor184or other type of display device is also connected to the system bus121via an interface, such as a video interface183. Computer110may also include a digitizer185for use in conjunction with monitor184to allow a user to provide input using a stylus input device186. In addition to the monitor, computers may also include other peripheral output devices such as speakers189and printer188, which may be connected through an output peripheral interface187.

The computer110may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer180. The remote computer180may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer110, although only a memory storage device181has been illustrated inFIG. 1. The logical connections depicted inFIG. 1include a local area network (LAN)171and a wide area network (WAN)173, but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.

When used in a LAN networking environment, the computer110is connected to the LAN171through a network interface or adapter170. When used in a WAN networking environment, the computer110typically includes a modem172or other means for establishing communications over the WAN173, such as the Internet. The modem172, which may be internal or external, may be connected to the system bus121via the user input interface160, or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer110, or portions thereof, may be stored in the remote memory storage device. By way of example, and not limitation,FIG. 1illustrates remote application programs182as residing on memory device181. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used.

Illustrative Embodiments of the Invention

One or more aspects of the invention may be embodied in computer-executable instructions (i.e., software), such as in a weather simulation software object, routine or function (collectively referred to herein as a weather simulation manager) stored in system memory130or non-volatile memory141,152,156as application programs135,145, program modules136,146, and/or program data137,147. The software may alternatively be stored remotely, such as on remote computer180with remote application programs182. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk141, optical disk156, removable storage media152, solid state memory, RAM132, etc. As will be appreciated by one of skill in the art, the functionality of the program modules may be combined or distributed as desired in various embodiments. In addition, the functionality may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like.

The weather simulation manager may be a component of a larger application program, such as a computer game that simulates weather as part of the gaming environment. Examples of such games may include, but are not limited to, flight simulation games, war simulations games, or any other game that takes place in a simulated virtual world. The larger application program might also be a computer based training application that trains users in a simulated real-world environment, or it may be any application program that simulates a virtual environment that relies in part on weather. The larger application program of which the weather simulation manager is a part may be referred to herein as the control program. As used herein, the term “computer game” refers to any game played on a personal computer, handheld computer, personal digital assistant, mobile phone, video game console, arcade game unit, and/or played on any other data processing device.

With reference toFIG. 2, aspects of the invention may include a method for dynamic weather simulation. In step201, the weather simulation manager initializes the weather, e.g., by obtaining or determining initial values for temperature and dew point for each of various regions in a simulated geographical environment (discussed in detail below). Next, in step203, the weather simulation manager determines whether clouds should form in each region. If clouds should form in a region, the weather simulation manager causes the computer system to graphically depict, also referred to as render, a layer of clouds in that region, in step205. Next, in step207, the weather simulation manager determines, for each of the various regions, whether each existing cloud layer should dissipate. If so, in step209, the weather simulation manager causes the computer system to dissipate the cloud layer determined to dissipate in step207. In step211, the weather simulation manager updates the weather conditions, e.g., including temperature and dew point, and returns to step203. Each of these general steps will now be described in more detail.

With reference toFIG. 3, the weather simulation manager may independently simulate weather using the method ofFIG. 2(as further described in detail below) for each of a plurality of cells305in a geographical grid307. Each cell305of the grid307corresponds to a predetermined geographic area within the simulated virtual environment. Because the user typically cannot see every location in the simulated environment at the same time, the weather simulation manager might only simulate weather for those cells located adjacent to, within a predetermined distance of, or within a predetermined radius of the user's current position301or current cell305. In an illustrative embodiment, each cell305may be a simulated 16 km×16 km area, extending away from the user in an approximately circular region303for a radius of 128 km. As the user moves within the simulated environment, cells may be added and removed from the set of cells for which weather simulation is performed as the cells come within and move beyond the predetermined distance, respectively. The cell sizes and predetermined distance may be increased or decreased, depending on the simulated visibility, performance capabilities of the computer system on which the weather simulation manager is running, and simulation regions other than circles may be used (e.g., rectangular, ellipse, triangular etc.).

In order to ensure that weather simulation does not affect other control program functions or other application programs running on the same computer system, the weather simulation manager may be allotted a predetermined amount of computer resources in which to perform weather simulation functions. In addition, the weather simulation manager might only perform weather simulation calculations for any given cell once within a predetermined amount of time, e.g., no more than once every ten seconds.

In an illustrative embodiment of the invention, the control program may allot the weather simulation manager a time slice, e.g., a fiber, every animation frame (preferably running at 30 frames per second or higher) in which the weather simulation manager can perform weather simulation functions. The weather simulation manager performs weather simulation calculations as described herein for as many cells within the region303as possible during each time slice. When the time slice is over, the weather simulation manager waits for the next allotted time slice and continues with the next cell in the region303. Prior to performing weather simulation calculations for a cell, the weather simulation manager may check to see if the current cell has had weather simulation calculations performed within a predetermined amount of time (e.g., 10 seconds in this example) and, if so, skips the cell. Those of skill in the art will appreciate that any time slice allotment may be used, e.g., based on fibers, threads, time, and the like, and any predetermined amount of time, including zero, may be used as the delay for weather simulation calculations for each cell.

Because the weather simulation manager performs weather calculations for each cell seaparately, different weather may be simulated in neighboring cells. This provides an increased sense of realism to the user because the weather simulation manager more closely mimics real world weather. That is, a user facing one direction might see mostly sunny skies and no rain, whereas if the user looks in the opposite direction in the simulated environment the user might see overcast skies and rain.

The control program (e.g., a flight simulation game) may be divided into phases. In a setup phase, a user may set parameters which may be used to control a subsequent game play phase. With reference back toFIG. 2, in step201the control program and/or weather simulation manager, during the setup phase or at the very beginning of a game play phase, initializes current weather conditions for each cell in the virtual environment. The weather simulation manager initializes weather conditions for cells within the predetermined distance303of the user's starting position301, and may also initialize global weather conditions outside that predetermined distance. Other ranges of cells for which weather conditions are initialized may alternatively be used. For each cell for which weather conditions are initialized, initial weather conditions may include surface conditions and winds aloft. Surface conditions may include, but are not limited to, temperature, dew point, wind speed, wind shear, wind turbulence and wind direction, cloud coverage (e.g., 0, ⅛, 2/8, . . . , 8/8; tenths may alternatively be used), cloud ceiling or base altitude, cloud height, cloud type, cloud turbulence, cloud icing, and atmospheric pressure. Winds aloft may include, but is not limited to, wind speed, wind direction, and temperature at altitudes from 3,000 feet up to 39,000 feet.

Weather initialization may be based on various sources. In one embodiment of the invention, with reference toFIGS. 6-11, the user may select a starting weather theme603from a weather menu601. The control program may have a default weather theme. For example, inFIG. 6, if the user selects or the default weather is the “fair weather” theme605, the weather might be initialized to 59 degrees Fahrenheit, ⅛ cloud coverage at 6,000 feet with a cloud height of 1,000 feet, and no surface wind.

Alternatively, when a user selects Real-world weather607or609, weather may be based in whole or in part on actual weather. When the simulated environment is a simulation of actually occurring geography (e.g., the United States or elsewhere on Earth), the weather simulation manager may download current weather conditions from a remote database182(FIG. 1) over the Internet173or some other network171. For example, the weather simulation manager may download surface weather conditions as METeorological Aerodrome Reports (METARs) provided by weather stations (other meteorological data providing reports may alternatively be used). METARs may be retrieved from Jeppesen Sanderson, Inc. of Denver, Colo. Alternatively, METARs may be retrieved from the National Weather Service. METARs are known in the art, and are available for approximately 6,000 weather stations in the world, approximately half of which are in the United States. For cells in which a METAR producing weather station is located, the weather simulation manager may use the data from that METAR producing weather station for that cell. For cells in which there is not a METAR producing weather station, the weather simulation manager may interpolate between METAR producing weather stations to arrive at the initial weather conditions for those cells.

If the user selects static Real-world weather607, the weather simulation manager might download current weather conditions once prior to beginning game play, and subsequent weather changes are as described below (not based on real weather). Alternatively, if the user selects auto-updated Real-world weather609, the weather simulation manager might download current weather conditions prior to beginning game play, and download subsequent weather changes periodically during game play, e.g., every 15 minutes. The weather may transition gradually to the newly downloaded weather over several minutes, rather than jumping abruptly to the new weather, as further described below. Weather may or may not change in-between real weather download intervals.

The user may alternatively select User-defined weather613, which may launch a custom weather menu701, illustrated inFIG. 7. Custom weather menu allows the user to change general weather conditions for any or all weather stations for which weather METARs may be received. The user may select an advanced weather option703to change more specific weather conditions.

Upon selection of advanced weather option703, the control program or weather simulation manager launches an advanced weather menu801, illustrated inFIG. 8, where the user can change specific weather conditions, including clouds, wind, temperature/pressure, and visibility, for any or all of weather stations for which weather METARs may be received. Each of clouds, wind, temperature/pressure, and visibility may have a sub-menu or tab803,805,807,809, respectively, through which the user can edit specific details for each respective condition.FIG. 8illustrates the advanced weather menu801and cloud sub-menu803, through which the user may be able to specify meteorological conditions for cloud type, cloud coverage, cloud tops, cloud base, turbulence, icing, and precipiation.FIG. 9illustrates the advanced weather menu and wind submenu805, through which the user may be able to specify meteorological conditions for wind altitude, wind speed, wind gusts, wind turbulence, shear strength, and wind direction.FIG. 10illustrates the advanced weather menu and temperature/pressure submenu807, through which the user may be able to specify meteorological conditions for altitude and dew point for various altitudes, as well as barometric pressure at sea level.FIG. 11illustrates the advanced weather menu and visibility submenu809, through which the user may be able to specify meteorological conditions for visibility at various altitudes. Within each submenu, the user may specify and/or modify weather conditions on a per weather station basis and/or for each of various altitudes, thus providing user-specified weather in three dimensions.

After initialization, the weather simulation manager begins weather simulation in step203by determining whether clouds should form in each cell within the predetermined distance of the user's current (starting) position. As indicated above, the weather simulation manager performs weather calculations for each cell separately (one of skill in the art will appreciate that weather for one cell may be based in part on weather in another cell, e.g., when the weather simulation manager interpolates a current cell's weather based on one or more weather stations located in one or more nearby cells). The method will be described with respect to a single cell, and those of skill in the art will appreciate that the same methods may be performed for each cell as applicable.

To determine if clouds should form in step203, the weather simulation manager first determines a cloud formation probability for the cell. The cloud formation probability may vary depending on the spread between the temperature T and dew point DP (referred to herein as the T/DP spread). Because cloud formation is checked relatively often (e.g., once every ten seconds in the above example), the cloud formation probability is preferably low so that cloud formation mimics real weather. For example, in one illustrative embodiment, when the T/DP spread is zero, the cloud formation probability 0.04 results in only a 4% chance of a cloud forming per minute (or per weather calculation cycle, or per some other amount of time). When the probability is based per minute, and the weather calculation cycle is less than one minute, then the probability may be adjusted accordingly. For example, if a weather calculation cycle for a cell occurs 20 seconds after the previous weather calculation cycle for that cell, then the probability may be divided by 3 (20 sec./60 sec.=⅓). As the T/DP spread increases, the cloud formation probability approaches zero. For example, the cloud formation probability may have a small value, such as 0.0125%, when the T/DP spread is greater than a predetermined spread, such as 50 degrees Celsius. Other probabilities may alternatively be used.

Upon determining the cloud formation probability, the weather simulation manager generates a random or pseudo-random number, collectively referred to herein as a random number, between 0 and 1. If the random number is less than the cloud formation probability, the weather simulation manager forms a cloud layer in step205. Otherwise, the weather simulation manager continues to step207.

In step205, the weather simulation manager determines what type of cloud layer to form, at what base altitude, and with what height.FIG. 4illustrates step205in more detail. In step401, the weather simulation manager determines the cloud coverage with which the cloud layer should be drawn. Cloud coverage is typically determined based on the percentage of sky covered by clouds. For example, meteorologists sometimes refer to cloud coverage based on Table 1:

Fraction of sky covered by cloudsCloud coverage description0/8Clear/Sunny⅛- 2/8Few Clouds/Mostly Sunny⅜- 4/8Scattered Clouds⅝-⅞Broken/Mostly Cloudy8/8Overcast
Alternatively, cloud coverage based on tenths or some other cloud coverage basis may be used, as is known in the art.

The weather simulation manager determines cloud coverage using Equation 1:
CC=CFAct/CFMax+RCC(Equation 1)
Where CC represents cloud coverage, CFAct. represents the actual cloud formation probability computed in step203, CFMax. represents the maximum cloud formation probability when the T/DP spread is zero, and RCCrepresents a random factor, e.g., ±50%, that may be added to CC. CC may be rounded up or down to the nearest ⅛ or other applicable fraction. The actual value of CC may be used to determine how much of the sky in the applicable cell the cloud layer should fill.

In step403, the weather simulation manager determines the cloud layer base altitude. The cloud layer base altitude may be determined using Equation 2:
CBA=((T−DP)×1000/2.5)+RCBA(Equation 2)
Where CBA represents Cloud Base Altitude in feet, Temperature T and Dew Point DP are in degrees Celsius, and RCBAis a random number such that −300<RCBA<300 feet, which provides for some randomness in the cloud base altitude. Other limits for the random number RCBAmay alternatively be used, or RCBAmay be set at zero to provide a uniform cloud base altitude. The Cloud Base Altitude may also be adjusted so that no two cloud layers overlap by more than a predefined amount, e.g., by no more than 60%. The constant value 2.5 represents an approximation of the temperature drop per 1,000 feet increase in altitude. Other approximations may be used, e.g., based on type of weather, degrees Fahrenheit versus degrees Celsius, etc. In one embodiment, 2.5 degrees per 1,000 feet may be used. Alternatively, 4 degrees per 1,000 feet may be a more accurate approximation in hot, sunny weather, whereas 2.5 degrees per 1,000 feet may be a more accurate approximation in cloudy, humid weather.

Finally, the weather simulation manager determines whether the cloud base altitude is low, medium, or high, and proceeds to steps405,411, or417, respectively. Low, medium, and high cloud base altitudes may be determined based on the relationships indicated in Equation 3:
Low≦2,000meters<Medium≦6,000meters<High  (Equation 3)
Other values may alternatively be used to delineate between low, medium, and high cloud based altitudes.

In step405, the weather simulation manager checks the current barometric pressure to determine what type of clouds to draw at low altitude. If the barometer is below 1007.4 millibars, then the weather simulation manager in step407renders a cloud layer of stratus type clouds at the determined cloud base altitude CBA with a predetermined height and according to the determined cloud coverage CC (i.e., the cloud layer covers the fraction of the sky determined by CC). The height may be statically set, e.g., to 2,000 feet, or the height may have an element of randomness. If in step405the barometer is greater than or equal to 1007.4 millibars, then the weather simulation manager in step409renders a cloud layer of cumulus type clouds at the determined cloud base altitude CBA with a predetermined height and according to the determined cloud coverage CC. The cloud height may be statically set, e.g., to 6,000 feet, or the height may have an element of randomness. Other barometer levels may be used as well.

If in step403the cloud base altitude falls within the medium range, the weather simulation manager checks the barometer in step411to determine what type of clouds to render. If the barometer is below 1007.4 millibars, then the weather simulation manager in step413renders a cloud layer of stratus type clouds at the determined cloud base altitude CBA with a predetermined height and according to the determined cloud coverage CC. The cloud height may be statically set, e.g., to 3,000 feet, or the height may have an element of randomness. If in step411the barometer is greater than or equal to 1007.4 millibars, then the weather simulation manager in step415renders a cloud layer of cumulus type clouds at the determined cloud base altitude CBA with a predetermined height and according to the determined cloud coverage CC. The cloud height may be statically set, e.g., to 8,000 feet, or the height may have an element of randomness.

If in step403the cloud base altitude falls within the high range, the weather simulation manager in step417renders a cloud layer of cirrus type clouds at the determined cloud base altitude CBA with a predetermined height and according to the determined cloud coverage CC. The cloud height may be statically set, e.g., to 500 feet, or the height may have an element of randomness.

The weather simulation manager may simulate a variety of stratus, cumulus, cumulonimbus, and cirrus type clouds. The weather simulation manager may select one type to render, as applicable, based on cloud base altitude and height, e.g., cirrostratus, altostratus, nimbostratus, stratocumulus, altocumulus, cirrocumulus, cumulonimbus, and the like.

After rendering the cloud layer, the weather simulation manager determines, in step419, whether precipitation is associated with the cloud layer. The precipitation determination may be based in whole or in part on cloud height, and on whether the temperature falls within a precipitation range, e.g., −10° C. at cloud altitude. If there is no precipitation, the weather simulation manager may continue to step207. If there is precipitation, the weather simulation manager in step421, determines whether the precipitation is rain, snow or some other form of precipitation (e.g., sleet, hail, etc.), and renders the applicable precipitation in the simulated geographic environment. In one embodiment, there is a 1% chance of snow and a 4% chance of rain. The precipitation may fall to the ground, or the weather simulation manager may simulate virga by simulating the precipitation falling only a predetermined distance below the cloud base, e.g., the precipitation falls for 2,000 meters below the cloud base.

In step207the weather simulation manager determines whether clouds should dissipate, i.e., be removed from the visually depicted scenery of the simulated environment. The weather simulation manager may determine cloud dissipation similar to the determination of cloud formation. To determine if clouds should dissipate, the weather simulation manager determines a cloud dissipation probability for cash cloud layer of the cell. Similar to the cloud formation probability, the cloud dissipation probability may vary depending on the spread between the temperature T and dew point DP. Because cloud dissipation is checked relatively often (e.g., once every ten seconds in the above example), the cloud dissipation probability is also preferably low. For example, in one illustrative embodiment, when the T/DP spread is zero, the cloud dissipation probability may be zero. As the T/DP spread increases to a high value, such as 50 degrees Celsius, the cloud formation probability approaches a maximum value, e.g., 0.04 (4%) or 0.039875 (3.9875%) chance of cloud dissipation per minute (or per weather calculation cycle). Conversely, when the T/DP spread decreases to 0, the probability approaches a minimum value, e.g., 0%. In one embodiment of the invention, in order to provide realistic cloud formation and dissipation, the cloud dissipation probability is the inverse of the cloud formation probability with respect to the maximum probability value, calculated as follows:
CDAct=CFMax−CFAct(Equation 4)
Where CDActrepresents the cloud dissipation probability, CFActrepresents the actual cloud formation probability computed in step203, and CFMaxrepresents the maximum cloud formation probability when the T/DP spread is zero. For example, if the maximum formation/dissipation probability CFMaxis 0.04 (4%) and the current cell's cloud formation probability CFActis 0.025 (2.5%), then the cloud dissipation probability CDActwould be 0.015 (1.5%). Those of skill in the art will appreciate that variations or other formulas may be used when determining cloud dissipation probabilities. The above formula is a representative example of a preferable manner in which to calculate cloud dissipation probabilities in a realistic manner.

Upon determining the cloud dissipation probability, the weather simulation manager generates a random number between 0 and 1. If the random number is less than the cloud dissipation probability, the weather simulation manager dissipates the existing cloud layer in step209. Otherwise, the weather simulation manager continues to step211. If the current cell for which weather calculations are being performed has no present cloud layers, steps207and209may be skipped for that cell, and the weather simulation manager may proceed directly from step203/205to step211, as applicable.

If the weather simulation manager determines that the cloud layer should dissipate, then in step209the weather simulation manager slowly makes the cloud layer graphically disappear from the simulated environment. In one illustrative embodiment, where each cloud is comprised of a three-dimensional volume of sprites, the weather simulation manager may gradually increase a transparency level (e.g., the A-value in an ARGB scheme) of sprites located at edges of the cloud. As the edge sprites' transparency level is increased or near transparent, the weather simulation manager may increase the transparency level of sprites closer to the center of the cloud as the farther out sprites fade from view. That is, the weather simulation manager increases the transparency level of the sprites located at the cloud's outer extremes. As those sprites begin to fade or disappear completely, the weather simulation manager begins to increase the transparency level of the next set of sprites that are now located at the cloud's outer extremes as a result of the original set of sprites fading from view and disappearing.

In step211the weather simulation manager updates the current weather conditions. Weather conditions may be modified based on any number of variables and in any number of manners. The method in which the weather is updated is secondary to the cloud determinations calculated based on the updated weather each calculation cycle (e.g., every 10 seconds in the above example). The weather update schema described herein is merely an example of one way in which the weather may be updated. Those of skill in the art will appreciate that alternative weather update schemas may be used instead.

During each cycle (i.e., every 10 seconds in the above example), the weather simulation manager may update the temperature and dew point, while other meteorological conditions may remain constant. Other meteorological conditions may be updated when the control program or weather simulation manager retrieves updated weather information from the database over the Internet. The rate with which the temperature and dew point change each cycle may be based on a variety of factors including, but not limited to, the position of the sun in the sky and the current cloud coverage for the respective cell. As the sun goes up during the day, the temperature and dew point generally increase, whereas as the sun goes down during the day, the temperature and dew generally decrease. Similarly, the temperature and/or dew point may be more likely to change when there is little cloud coverage than when there is greater cloud coverage. In addition, the existing T/DP spread may be used as an indication of humidity, which may further affect the rates of change for temperature and dew point. Temperature and dew point may change independently of each other while following their respective increasing/decreasing trend.

While the trend for the change may be to generally increase or generally decrease over longer periods of time, each of the temperature and dew point may increase or decrease with each cycle. For example, during an increasing trend, the range with which the temperature and/or dew point can change may include a small probability of decreasing and a larger probability of increasing. The possible range of temperature change with no cloud coverage may be from −0.01 to 0.05 degrees per minute (or per weather calculation cycle), and the weather simulation manager may randomly select a value within this range by which to alter the temperature. Thus, while there is a possibility that the temperature may decrease, there is a much larger probability that the temperature will increase. The same or a different range may be used for the dew point and opposite ranges or other ranges weighted towards decreasing values may be used when the temperature and/or dew point trend is to decrease.

As indicated above, the temperature and dew point changes may be based on the sun's position in the sky as well as on cloud coverage. Temperature and/or dew point changes may further be based on a ‘reality’ setting that alters the changes based on whether the changes should attempt to mimic real weather, be more extreme than real weather, or be milder than real weather. In one illustrative embodiment, with reference toFIG. 5, a user may set a dynamic weather variable501(e.g, a slider) to any of a plurality of positions, e.g., none, mild, medium, high, extreme. A default value may be set to the ‘medium’ setting, which attempts to mimic actual rates of change of real weather patterns. The mild setting may cause the rate of change to be less than real weather, and the none setting may cause temperature and dew point to remain constant throughout game play. The high setting may cause the rate of change to be more than real weather, and the extreme setting may cause rates of change to be a lot more than real weather (e.g., variations of 40 degrees Celsius per day).

The selected setting may act as a multiplier for the temperature and/or dew point change. For example, the none setting may multiply the temperature and/or dew point change by 0, resulting in no change; the mild setting may multiple the temperature and/or dew point change by 0.5, resulting in less change than real weather; the medium setting may multiple the temperature and/or dew point change by 1, resulting in real weather; the high setting may multiply the temperature and/or dew point change by 3, resulting in greater than normal temperature and dew point variations; and the extreme setting may multiply the temperature and/or dew point change by 10, resulting in extreme temperature and dew point variations as compared to real life. Alternatively, additional or different settings may be used, or the user may select any arbitrary multiplier within the range of valid multipliers.

When updating the weather in step211, the weather simulation manager may perform one or more error checks including, but not limited to, ensuring that the dew point does not exceed the temperature. That is, the dew point should be lower than or the same as the temperature. If the weather simulation manager otherwise attempts to change the temperature and/or dew point in such a manner that the dew point would exceed the temperature, the weather simulation manager forces the dew point and temperature to the same value (e.g., either the calculated temperature or dew point, or some range in between), or forces the dew point to be less than the temperature. In addition, the weather simulation manager may ensure that the temperature, at ground level never exceeds or falls below a certain temperature range. For example, the weather simulation manager may ensure that the temperature T at ground level stays within the range −50° C.≦T≦50° C.

If the user, prior to beginning game play or dynamically in the middle of game play, selects updated Real-world weather609(FIG. 6), the weather simulation manager may retrieve updated real world weather conditions from the database over the Internet at regular intervals, e.g., every 15 minutes. The regular intervals in which weather is retrieved from the database are generally much larger than the cycle intervals in which the weather simulation manager updates weather for each cell (e.g., approximately every 10 seconds in the above example). Therefore, there is a likelihood that the simulated weather will be quite different from the real-world weather by the time the next real world weather update occurs. This is especially the case when the user's dynamic weather setting501(FIG. 5),611(FIG. 6) is set to other than the medium setting.

Thus, in one embodiment, upon retrieving updated real world weather, the weather simulation manager may revert the weather back to real world weather. However, to provide a smooth user experience during game play, the weather simulation manager might not immediately change the current weather for each cell to the updated real world weather. To do so might cause unrealistic weather events and/or confuse the user. Instead, the weather simulation manager may gradually morph each cell's current weather to the retrieved updated real world weather over some predetermined amount of time, e.g., over the next three minutes of game play. This provides a smooth transition back to real weather. After the transition back to real weather, the weather simulation manager may revert back to the user settings to determine subsequent weather changes during each cycle.

In some embodiments, the weather simulation manager might not simulate weather conditions other than temperature and dew point. That is, the weather simulation manager, during each cycle, might not alter other weather conditions such as winds aloft and barometric pressure. Instead, these other weather conditions may be updated at the periodic intervals in which weather is retrieved from the database over the Internet.

Thus, using the methods and systems described above, the weather simulation manager can provide dynamic weather based on real weather, based a user's individual weather settings, or any combination thereof. The weather simulation manager can simulate real world weather, making the user feel part of a larger world, or weather that changes more or less dramatically than real world weather. By independently simulating weather for each cell in a geographic grid, a variety of weather types may be simulated simultaneously, further increasing the realistic look and feel of the simulated weather.

While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims.