WO1993002427A1

WO1993002427A1 - Time-division multiplexed image generation

Info

Publication number: WO1993002427A1
Application number: PCT/US1992/005040
Authority: WO
Inventors: Kenneth R. Brooke
Original assignee: Hughes Aircraft Company
Priority date: 1991-07-24
Filing date: 1992-06-15
Publication date: 1993-02-04

Abstract

A visual simulation system (10') and method for digital computer graphics processing is described whereby the system (10') generates a plurality of digital computer images for parallel display on a plurality of output display devices (22'). Time Division Multiplexed Image Generation (TDMIG) is accomplished by providing a computer model (32') and a plurality of display channel definitions (34') as inputs to the image generation channel (24') for processing in the display processing unit (16') in a time-divided sequence and directing the outputs of the display processing unit (16') to separate display channels (26'). Each display channel (26') is serviced by the full capacity of the image generator (14') and, therefore, retains the maximum graphics processing and resolution capability of the image generator (14'). However, each display channel is updated at a rate of 1/N times the frame update rate of the image generator (14'), where N equals the number of display channels (26') in the visual simulation system (10') configuration.

Description

TIME-DIVISION MULTIPLEXED IMAGE GENERATION

BACKGROUND OF THE INVENTION Technical Field

This invention relates to digital computer graphic processing and is especially applicable for- use in th image generators of visual simulation systems.

2. Discussion

Typically, visual simulation system digital compute graphics processing configurations are tightly integrated, having an image generator with a single image generation channel which services a single display channel. This structure inherently monopolizes the use of the most expensive of the digital computer graphics processing components of a visual simulation system, the image generator. Techniques for transmitting several messages or signals simultaneously on the same channel or circuit, known as multiplexing, are well known. Time-division multiplexing, although a common technique in the communications field, has not found use in the image generators of visual simulation systems. Instead, spatial multiplexing has been used in digital computer graphi processors, and is known in the art as "windowing."

Windowing divides the processing capacity of an imag generation channel between multiple display channels, wit each display channel describing a separate "window" on th output display device. In addition, windowing allow multiple display channels to be serviced by the imag generation channel while maintaining the image generator' frame update rate, which is typically on the order of on sixtieth of a second. However, because the resolution o the image generator is divided, each display channel i inherently limited as to the visual complexity of the imag it can describe.

However, in some specialized visual simulation syste applications, the need to maintain the visual complexity i each of a plurality of display channels is greater than th need to maintain the maximum capable frame update rate o the image generator. Therefore it is desirable for th image generator in a visual simulation system to provide single image generation channel which services a pluralit of display channels having the resolution and visua complexity desired in the simulation in a time-divide sequence. An example of a visual simulation syste application which would benefit from time-divisio multiplexing is illustrated by an aircraft flight simulato simulating the cockpit of an aircraft having several windows, where each window is represented by a separate output display device. SUMMARY OF THE INVENTION According to the teachings of the present invention, a visual simulation system and method for digital computer graphics processing is described whereby the system generates a plurality of digital computer images for parallel display on a plurality of output display devices. Time Division Multiplexed Image Generation (TDMIG) is accomplished by providing a computer model and a plurality of display channel definitions as inputs to the image generation channel for processing in the display processing unit in a time-divided sequence and directing the outputs of the display processing unit to separate display channels. Each display channel is serviced by the full capacity of the image generator and, therefore, retains the maximum graphics resolution capability of the image generator.

BRIEF DESCRIPTION OF THE DRAWINGS The various advantages of the present invention will become apparent to one skilled in the art upon reading the following specification in which:

FIG. 1 is a simplified block diagram showing the digital computer graphics processing components of a conventional visual simulation system; and FIG. 2 is a simplified block diagram illustrating the digital computer graphics processing components of a visual simulation system configured for use with the time-division multiplexed image generation of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT It should be understood from the outset that while t present invention will be described primarily in connecti with one specific example, this example is simply a be mode of currently practicing the invention and that oth modifications can be made to this specific example witho departing from the spirit and scope of the invention.

Referring now to the drawings, a simplified bloc diagram showing the digital computer graphics processin components of a conventional visual simulation system (VSS 10 is illustrated in FIG. 1. The digital computer graphic processing components of a conventional VSS 10 shown ar well-known in the art and include a general purpose digita computer 12, an image generator (IG) 14 having a displa processing unit (DPU) 16, a video display buffer 18, and digital-to-analog converter 20, and an output displa device 22. A single image generation channel 24 runnin between the digital computer 12 and the DPU 16 services th IG 14 _r and a single display channel 26 running between th DPU 16 and the video display buffer 18 services the outpu display device 22. In a conventional VSS 10, the digita computer graphics processing begins in the digital compute 12 which operates under the control of an applicatio program 28 executing in its programmable memory 30. Th application program 28 generates data for graphic processing in the IG 14. The IG 14 then interprets th data and, in turn, generates an output which i subsequently interpreted and displayed by the outpu display device 22 for physically representing each frame o a simulation.

For each frame of the simulation, the applicatio program 28 executing in the digital computer 12 generate a set of data which describes a computer mode corresponding to the physical environment that is to b simulated by the VSS, such as aircraft in an aircraf flight simulator, for example. This set of data contain relevant information about the descriptions and propertie of objects in that environment as well as information abou relationships among the data. This set of data is commonl referred to in the art as a visual data set or compute model 32. In conjunction with the computer model 32, th application program 28 also generates a display channe definition 34. The display channel definition 34 is separate set of data which describes the viewin specifications, such as the look angle, field of view, an other descriptors, for example, according to which th computer model 32 will be viewed in that frame of the simulation. It is the display channel definition 34 tha describes the orientation of the computer model 32 to the IG 14 so that the IG 14 can generate the appropriate digital computer image for each frame in the simulation.

The digital computer 12 then instructs the IG 14 to process the computer model 32 in accordance with the viewing specifications of the display channel definition 34. The IG 14, in performing its function of generating an output for display on the output display device 22, completes two tasks: scan conversion and digital-to-analo conversion.

The first task of the IG 14 is to generate a digita computer image, also known as a raster, which renders th 5 visual scene desired in the simulation. This task i performed by the DPU 16. The DPU 16 creates the raster b converting the computer model 32 as oriented by the displa channel definition 34 into a finite array of discree picture elements, called pixels. Each pixel is assigned 10 display color value which corresponds to the color of tha portion of the computer model 32 which the pixe represents. The display color value is defined by thre integer components, each component representing one of th three primary colors red, green, and blue. Thi 15 information is commonly referred to in the art as RGB dat or pixel data. The pixel data output of the DPU 16 is the stored in the video display buffer 18. This process o converting the computer model 32 into the pixel data of raster is well-known in the art as scan conversion. 20. The second task of the IG 14 is to generate a vide signal that can be interpreted by the output display devic 22 so that it may physically render the raster as a visibl image. This task is accomplished by the digital-to-analo converter 20. The pixel data stored in the video displa 5 buffer 18 are processed by the digital-to-analog converte 20 and are transformed from digital data into an analo video signal that can be interpreted by the output display device 22. This process is well-known in the art as digital-to-analog conversion.

Finally, the output display device 22, such as a cathode-ray tube, for example, interprets the analog video signal and displays the raster. Digital computer graphics processing for each frame of the simulation in a conventional VSS 10 is accomplished in a period of time on the order of about one-sixtieth of a second.

It is well-known that in a conventional VSS 10, the digital computer graphics processing configuration is tightly integrated such that the IG 14, and specifically the DPU 16, services only a single display channel 26 providing output for a single output display device 22. However, some visual simulation systems require that the IG 14 have the capability of processing a plurality of display channel definitions 34 for a given computer model 32 for generating output for a plurality of output display devices 22. One such example is an aircraft flight simulator having multiple displays corresponding to the separate windows in the aircraft cockpit being simulated. The present invention allows such a VSS to process a plurality of display channel definitions 34 through a single image generation channel 24 for generating a plurality of outputs for parallel display on a plurality of output display devices 22. An important advantage of the present invention is that the use of a single image generator 14 is amortized among a plurality of display channels 26, thereby significantly reducing the total cost of such VSSs. Turning now to FIG. 2, a simplified block diagr illustrating the digital computer graphics processi components of a VSS 10' configured for use with the tim division multiplexed image generation (TDMIG) of t present invention is shown.

It is important to point out that although t specific VSS embodiment illustrated in the followi discussion is directed toward the time-divided multiplexi of four display channel definitions through the sing image generation channel of an IG for servicing fo display channels, such as in an aircraft flight simulator for example, this particular embodiment is only an exampl and in no way limits or restricts the application of th present invention to any definite number of digita computer graphics processing components, including displa channels.

Together with the digital computer graphics processin components of a conventional VSS 10 discussed previously a VSS 10* configured for TDMIG includes a demultiplexer, o ^■ routing switch 36, and a switch control channel 38. I addition, the VSS 10' shown here has a separate displa channel 26^»A, 26'B, 26*C, 26'D, addressable video displa buffer 18'A, 18'B, 18'C, 18'D, and digital-to-analo converter 20'A, 20*B, 20'C, 20'D, for each of the outpu display devices 22'A, 22'B, 22*C, 22'D, required for th simulation. However, there is still only a single imag generation channel 24'. The routing switch 36 acts t alternate the output of the image generator 16^■ between th separate display channels 26'A, 26'B, 26'C, 26'D, an operates under the control of the application program 28 by way of the switch control channel 38. An example of routing switch 36 which may be used' in this configuratio of the present invention is a programmable ASI (application specific integrated circuit) .

As already described, the application program 28 operates in the programmable memory 30' of the digita computer 12' and generates a computer model 32' in a well known manner. Next, the application program 28' generate a plurality of display channel definitions 34'A, 34*B 34'C, 34'D, each display channel definition 34 corresponding to a separate display channel 26' and havin the unique viewing specifications required by th simulation for the output display device 22' which tha display channel 26* services. In addition to the usua descriptors typically found in a display channel definitio 34, each display channel definition 34' here has a uniqu channel identifier so that it is separately addressable i the memory 30' of the digital computer 12'.

The application program 28' then instructs the IG 14 ' to process the computer model 32' according to the firs display channel definition 34'A in the typical manner fo generating the first channel pixel data output. Next, th first channel pixel data are directed through the routin switch 36 for routing to the first display channel 26'A, the routing switch 36 being initially set to the firs display channel 26'A. Finally, the first channel pixe data are stored in the first video display buffer 18*A after which, the first digital-to-analog converter 20' converts the first channel pixel data into an analog vide signal for the first output display device 22'A as wa previously described.

After the computer model 32* has been processe according to the first display channel definition 34'A, th application program 28* instructs the routing switch 36 t index its setting to the second display channel 26'B. Th application program 28* then instructs the IG 14' t process the computer model 32' according to the secon display channel definition 34'B. The procedure is repeate so that as the computer model 32' is processed according to each display channel definition 34', the routing switch 36 directs the output of the image generator 16' to the appropriate display channel 26¹.

It can be appreciated that the time-divided multiplexed image generation of the present invention operates to generate a plurality of images by providing a sequence of inputs consisting of a plurality of display channel definitions to the image generation channel for processing in the DPU in a time-divided sequence and directing the outputs of the DPU to separate display channels. Each display channel is serviced by the full capacity of the image generator and, therefore, retains the maximum graphics processing capability and resolution of the image generator. However, each display channel may be updated at a rate of 1/N times the frame update rate of the image generator, where N equals the number of display channels in the visual simulation system configuration. The present invention, therefore, allows the VSS designer to share the image generation channel between a plurality of display channels, and amortize the cost of the most expensive component of the VSS, image generator. Further, it is expected^' that the present invention may incorporated in a conventional VSS inexpensively and with a minimum of modifications. Various other advantages and modifications will become apparent to one skilled in the art after having the benefit of studying the teachings of the specification, the drawings, and the following claims.

Claims

CLAIMS What Is Claimed Is:

1. A visual simulation system- for digital compute graphics processing, comprising: a) means for generating a computer model and plurality of display channel definitions for eac ^■ frame in a visual simulation; b) means for separately processing the compute model according to each display channel definition in a time-divided sequence and generating a plurality of digital computer images; c) means for routing each digital computer image through a separate display channel; and d) means for displaying each digital computer image on a separate output display device; whereby the system generates a plurality of digital computer images for parallel display on a plurality of output display devices.

2. The visual simulation system of Claim 1 further comprising means for identifying each display channel definition.

3. The visual simulation system of Claim 2 further comprising means for separately addressing each display channel definition based upon its identification.

4. The visual simulation system of Claim 1 wherei the means for separately processing the computer mode comprises: means for providing the computer model and eac display channel definition to an image generatio channel in sequence; and an image generator being serviced by the image generation channel.

5. The visual simulation system of Claim 4 wherein the means for routing the digital computer images comprises: means for directing the output of the image generator corresponding to each digital computer image to a separate display channel; and means for controlling the display channel to which the digital computer image is directed.

6. The visual simulation system of Claim 1 wherein the means for displaying each digital computer image comprises: means for storing each digital computer image; means for converting each digital computer image into an analog video signal; and means for providing each analog video signal to an output display device.

7. The visual simulation system of Claim 6 wherein said means for storing each digital computer image comprises a plurality of separately addressable video display buffers, each being serviced by a separate display channel.

8. The visual simulation system of Claim 7 wherein said means for converting each digital computer image into an analog video signal comprises a plurality of digital-to- analog converters, each corresponding to a separate output display device.

9. The visual simulation system of Claim 1 wherein the visual simulation system is a flight training visual simulation system.

10. The visual simulation system of Claim 9 wherein the flight training visual simulation system is an aircraft flight simulator in which a plurality of output display devices correspond to separate windows in an aircraft cockpit.

11. A method of digital computer graphics processin in a visual simulation system, comprising: a) generating a computer model and a plurality o display channel definitions for each frame in a visua simulation; b) processing the computer model according to eac display channel definition in a time-divided sequenc and generating a plurality of digital computer images c) routing each digital computer image through separate display channel; and d) displaying each digital computer image on separate output display device; whereby to generate a plurality of digital computer image for parallel display on a plurality of output displa devices.^'

12. The method of digital computer graphic processing of Claim 11 further comprising before step (b) the step of identifying each display channel definitio generated.

13. The method of digital computer graphic processing of Claim 12 further comprising before step (b the step of separately addressing each display channe definition based upon its identification.

14. The method of digital computer graphic processing of Claim 11 wherein step (b) comprises: providing the computer model and each displa channel definition to an image generation channel i sequence; and processing the computer model according to eac display channel definition in an image generator bein serviced by the image generation channel.

15. The method of digital computer graphic processing of Claim 14 wherein step (c) comprises: directing the output of the image generato corresponding to each digital computer image to a separate display channel; and controlling the display channel to which the digital computer image is directed.

16. The method of digital computer graphics processing of Claim 11 wherein step (d) comprises: storing each digital computer image; converting each digital computer image into an analog video signal; and providing each analog video signal to an output display device.

17. The method of digital computer graphics processing of Claim 16 wherein each digital computer image is stored in a separately addressable video display buffer being serviced by a separate display channel.

18. The method of digital computer graphic processing of Claim 17 wherein each digital computer imag is converted into an analog video signal in a digital-to analog converter corresponding to a separate output displa device.

19. The method of digital computer graphic processing of Claim 11 wherein the visual simulation syste is a flight training visual simulation system.

20. The method of digital computer graphics processing of Claim 19 wherein the flight training visual simulation system is an aircraft flight simulator in whic a plurality of output display devices correspond to separate windows in an aircraft cockpit.