GB2358919A

GB2358919A - Measuring and modelling light distribution

Info

Publication number: GB2358919A
Application number: GB0001629A
Authority: GB
Inventors: Andrew Steven Russell
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-01-26
Filing date: 2000-01-26
Publication date: 2001-08-08
Anticipated expiration: 2020-01-26
Also published as: CA2332156A1; GB0001629D0; AU781270B2; GB2358919B; AU1641701A

Abstract

A light monitoring device 1 comprises at least one light sensitive element 25 and recording means 40, wherein the output from the or each element 25 is recordable by the recording means 40, the recorded data being related to the lighting conditions around the device 1. The light sensitive elements may be mounted on a sphere (fig 2). Also provided is a lighting system comprising the light monitoring device 1 and a computer 100, wherein the output from each of a plurality of light sensitive elements 25 is loadable into a memory of the computer; a programme running on the computer being able to extract the memorised data and construct a virtual spacial distribution of light, related to that detected by the elements and impose the light conditions upon a virtual object within a virtual studio.

Description

2358919 MONITORING DEVICE AND METHOD

DESCRIPTION

This invention relates to a monitoring device and, more specifically, to a light monitoring device which may be used during film making, as well as to a corresponding method.

Current advances in computer technology are such that computer- io generated images are routinely incorporated into cinema films, television programs, promotional videos and commercials.

In order to produce a shot in which a computer-generated image is incorporated, the background and any "real" actors, props and scenery are first filmed. The film is then transferred, in electronic form, to a computer where it is stored.

A computer artist, who has previously generated the riSquired images, will then incorporate those images into the film in what is known in the art as a "virtual studio". The complex motion of the generated image as well as the interaction of the so-generated "virtual" image with the "real" actors, landscape and properties requires a great deal of expertise to perfect. Indeed, a large number of factors have to be addressed when such an image is created.

In order to convince an audience that the virtual image is a real and integral component of the finished film a polished effect must be achieved by the artist. This requires that the "real" components interact with the "virtual" parts and that the "virtual" parts look as if they are a part of the "real" scene.

An important factor in achieving a convincing effect is the play of light over the "real" and "virtual" components. Thus a computer artist will instruct the computer to determine the position of the light source and the computer will calculate the effect that the light would have had if the virtual component had been present in the real scene. The computer is then instructed to apply that lighting effect to the virtual component, and make corresponding virtual alterations to the film. Such alterations take into account the relationship between the light source and the virtual component, such as the casting of a shadow by the virtual component on to a real aspect of the scene.

Such techniques are normally most effective in open "real" scenes with a single light source. Such as during daylight in a wide plain for example, or at night in total or near total darkness illuminated by distinct artificial lighting. However, whilst it may be a relatively simple task for the computer to calculate the lighting effect in such circumstances, in others it is an almost impossible task.

For example, in scenes where there are many diffuse light sources and in ones where light is reflected off of different surfaces it is difficult for the computer to accurately calculate the effect that the virtual component would have in the "real" scene. For example, light reflected off of a partially reflective surface placed behind the virtual component may result in a slight back-lighting effect.

Whilst a frame of film in isolation may appear to correctly locate the virtual component, once several frames are run together the brain of a viewer begins to detect the minute differences between the computer enhanced or altered image and that expected from learned experience. Thus, the images are interpreted and understood to have been generated by a computer and computer artist.

Accordingly it is an object of the current invention to provide a device which can monitor light levels and provide the so-monitored data in readable form such that it may be incorporated when creating a computer generated image.

According to a first aspect of the invention there is provided a light monitoring device comprising at least one light sensitive element and recording means, wherein the output from the or each element is recordable by the recording means, the so-recorded data being related to the lighting conditions around the device.

The terms lighting conditions or light condition, as used herein, refers to inter alia the spatial light distribution and spatial light intensity distribution. Such terms refer to the three-dimensional distribution of light which is experienced by an object at a particular location or at a particular point in time. Thus, the intensity of light and/or the brightness of the light at points around and about the object comprise the spatial distribution. The greater the number of points around the object at which the light intensity and/or brightness is detected and measured the "finei", which is to say the greater the resolution, the spatial distribution.

Preferably the device comprises a plurality of elements, all of which are mounted in or on a housing.

The housing may be an oblate spheroid or it may be spherical, pyramidal or polyhedral. The elements may be mounted in a regular or irregular array in or on the housing.

The output from the or each element may be recorded in real time or at distinct intervals, the so-recorded data being accorded a time component such that the temporal variation of output of the or each element is recorded.

The or each element may comprise a photodiode, the or each of which may have associated therewith an analogue-to-digital converter (ADC). The or each ADC may be accommodated within the housing, the output from which may be recordable by the recording means.

The recording means may be accommodated within the housing or alternatively external thereto. The external recording means may be provided by a computer.

The recording means may record the data in computer readable form such that it is loadable into the memory of a computer, whereupon it may be processed by a program running on the computer, the computer program preferably being able to construct the light conditions within a virtual studio. The computer program additionally may construct a temporal framework for the light conditions.

Additionally the program may be able to impose the light conditions upon a virtual object in order that the virtual object is lit accoiding to the conditions at the time of detection. The program may also be able to impose the temporal variation of the light conditions upon the virtual object.

A second aspect of the invention provides a lighting system comprising a light monitoring device and a computer, wherein the output from each of a plurality of light sensitive elements comprising the device is loadable into a memory of the computer, a program running on the computer being able to extract the memorised data and construct a virtual spatial distribution of light, related to that detected by the elements, and impose the light conditions upon a virtual object within a virtual studio.

The temporal variation of the output from each light sensitive element may be recorded and the program may be able to impose the temporal variation of light conditions upon the virtual object.

According to a third aspect of the invention there is provided a method of creating a realistically lit virtual object comprising the steps of, detecting light intensity with a plurality of spatially arranged light sensitive elements; transferring the output from each of the elements, or at least data corresponding thereto, to a computer; constructing virtual light conditions corresponding to that detected by the elements; and imposing the virtual light conditions upon a virtual object.

The method may further comprise the steps of, recording the temporal variation of output from each element; constructing a virtual light condition which varies according to the temporal variation in output from each element; and imposing the temporally varying condition upon an animated virtual object such that the lighting upon the object varies in accordance with variations detected by the elements.

In order that the various aspects of the invention may be fully understood embodiments of the invention, in accordance therewith, will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is an isometric view of a first embodiment of the inventive device; Figure 2 is an isometric view of a second embodiment of the inventive device; and Figure 3 is a schematic diagram of a lighting system comprising the second embodiment.

Referring firstly to Figure 1, there is shown a light monitoring device 1 comprising a cuboid housing 10 having, in the centre of each face thereof, a light detecting element 5. Light impinges against an element 5 which, as a io result, produces an output proportional to the brightness or intensity of light impinging thereon.

Referring now to Figure 2, there is shown a second light monitoring device 20 comprising a spherical housing 30 having mounted thereon, in a regular array, a plurality of light detecting elements 25. The housing is also provided with a handle 35 from which the housing 30 may depend or be supported.

Figure 3 shows a schematic diagram of a lighting system, generally indicated at 55, comprising the light monitoring device 20. Light, as represented by the arrows hv, impinges upon the light detecting elements 25, causing a signal, proportional to the intensity or brightness of light experienced, to be outputted from each element 25. The signal from each element 25 is stored in recording means 40 accommodated within the housing 30. The signal can be converted from that output from each element 25 to a signal suitable for recording by a dedicated converter 45. The output from each element may be analogue in nature, in which case the converter 40 may be an analogue-to-digital converter (ADC) to provide a digital signal to be recorded by the recording means 40.

The data held within the recording means 40 is transferred to an external recording means 50 by a hard wire connection 48 which may be plugged into a suitable output port 3 8 situated on the housing 3 0, or preferably on the handle 3 5. The so-recorded data may be loaded into a memory 60 of a computer 100, wherein it is converted into a virtual light condition by a program operating within the computer 100.

A computer artist, via the user interface 70, may request that the computer 100 imposes the virtual light condition, such as the spatial light io intensity distribution, upon a virtual object within a virtual studio, and subsequently view the results via the interface 70.

If an animated virtual object is required, the temporal variation in output from each element 25 is recorded. The computer 100 converts the data into a temporally defined light condition, for example a spatial light intensity distribution, which may be imposed upon the virtual animated virtual object. The computer 100 calculates the effect of the light as it would play over the surface of the object as it moves, thereby lighting the object, vithin the virtual studio, in accordance with the lighting conditions detected by the elements 25.

If the temporal variation in output from each element 25 is required, care is taken to ensure that the converters 45 are able to convert the signal with the required time resolution, and that the recording means 40 can similarly record at a sufficient rate.

In some cases the "on-board" recording means 40 can be dispensed with and the signal from each element 25 sent directly to the external recording means 50. In such a case the connection 48 allows the output from each element 25 to be sent along a dedicated channel and recorded at the 3o external means 50.

The light sensitive elements 5, 25 can be any suitable element known in the art, although the favored element 5, 25 comprises a photodiode array. Such two-dimensional arrays allow each photodiode to simultaneously register the light impinging thereon and a signal is gathered thereby. The associated electronics are housed within the housing 10, 30, as are, if required, filters to ensure a high signal-to-noise ratio.

In order to create a film, video or commercial incorporating a virtual object within a "real" setting, the setting is filmed with any real components required. Thus, actors perform their roles interacting as necessary with the scene and with the as yet imaginary virtual component. Well- established techniques, such as "blue-screening", may be used to allow an actor to take the place of the virtual object within the real scene. Thus the proxy virtual object can interact with the real components of the scene, knock things over, cause splashes and so on.

Whilst the scene is being filmed, a light monitoring device 5, 20 is used to detect and subsequently record the actual lighting conditions present. The device 5, 20 detects the spatial distribution of light present at the time of filming. Moreover, it may be placed at the location which it is intended the virtual object will occupy to detect and record the lighting conditions at that point in space and time.

As stated above, the data are converted into, for example, a virtual spatial light distribution in the virtual studio, whereupon the distribution may be imposed upon the virtual object. In situations where the virtual object has a complicated surface the computer calculates how that surface will interact with the light conditions and alters the image accordingly. Similarly, the effect that the virtual object has on the light experienced by the other components in the shot may also be calculated and alterations made to the shot within the virtual studio.

Such processing steps may be automated, requiring little or no input from the computer artist once th e position of the virtual object within the C9real" scene has been established.

The light monitoring device, its associated electronics and the computer software and hardware enable a computer artist to give a computer generated image, which is to be incorporated into "real" scene, a much more natural appearance as the lighting is essentially the same as that experienced on the actual "shoot". Thereby providing a much more convincing finished film.

It is noted that the housing 10, 30 may be of any suitable shape, an oblate spheroid, a sphere, pyramid or any polyhedron for example. It can be suspended ftom the ceiling, for example, hand-held or mounted on a suitable stand. However, when setting up the device 1, 20 the alignment of the array of elements 5, 25 with respect to a fixed point in the scene is recorded. This enables the accurate location of the virtual light conditions wilin the virtual scene. Furthermore, the light sensitive elements 5, 25 may be situated in an irregular array over the surface of the housing 10, 30. The elements may be positioned at the corners of an object rather than on or in the faces as in the first embodiment.

In certain'cases, the housing may be the shape of the virtual object to be incorporated into the film. Thereby enabling the device to "capture", as close as possible, the lighting conditions which would have been experienced by the virtual object, if it had been present at the time of filming. The housing may therefore be a moving or static model of the virtual object as required.

Whilst the above-exemplified embodiments relate to uses within the film or video production industries many other uses are envisaged. For example, light monitoring as part of a scientific study. In such cases the light sensitive elements need not record light in the visible part of the spectrum. Suitable infrared and ultra violet detectors may be used to provide a spatial distribution of intensities in those respective parts of the spectrum.

Claims

1. A light monitoring device comprising at least one light sensitive element and recording means, wherein the output from the or each element is 5 recordable by the recording means, the so-recorded data being related to the lighting conditions around the device.

2. A device according to claim 1 comprising a plurality of elements, all of which are mounted in or on a housing.

3. A device according to claim 2, wherein the housing is an oblate spheroid or it is of spherical, pyramidal or polyhedral form.

4. A device according to claim 2 or 3, wherein the elements are mounted in a is regular array in or on the housing.

5. A device according to claim 2 or 3, wherein the elements are mounted in an irregular array in or on the housing.

6. A device according to any preceding claim, wherein the output from the or each element is recordable in real time, the so-recorded data being accorded a time component such that the temporal variation of output of the or each element is recorded.

T A device according to any preceding claim, wherein the output from the or each element is recordable at distinct intervals, the so-recorded data being accorded a time component such that the temporal variation of output of the or each element is recorded.

8- A device according to any preceding claim, wherein the or each element comprises a photodiode, the or each of which has associated therewith an analogue-to-digital converter (ADC).

s

9. A device according to claim 8, wherein the or each ADC is accommodated within the housing, the output from each of which is recordable by the recording means.

10. A device according to any preceding claim, wherein the recording means is accommodated within the housing.

11. A device according to claim 10 further comprising external recording means.

12. A device according to any of claims 1 to 9, wherein the recording means is external to the housing.

13. A device according to claim 11 or 12, wherein the external recording means is provided by a computer.

14. A device according to any preceding claim, wherein the recording means is arranged to record the data in computer readable form such that it is loadable into the memory of a computer.

15. A device according to claim 14, wherein said loaded data is processable by a program running on the computer, the computer program being able to construct the light conditions within a virtual studio.

16. A device according to claim 15, wherein the computer program is able to construct a temporal framework for the light conditions.

17. A device according to claim 15 or 16, wherein the program is able to impose the light conditions upon a virtual object in order that the virtual object is lit according to the conditions at the time of detection.

18. A device according to claim 16 or 17 when dependent upon claim 16, wherein the program is able to impose the temporal variation of the light conditions upon the virtual object.

19. A lighting system comprising a light monitoring device and a computer, wherein the output from each of a plurality of light sensitive elements comprising the device is loadable into a memory of the computer, a program running on the computer being able to extract the memorised data and construct a virtual spatial distribution of light, related to that detected by the elements, and impose the light conditions upon a virtual object within a virtual studio.

20. A system according to claim 19, wherein the temporal variation of the output from each light sensitive element is recordable.

21. A system according to claim 20, wherein the program is able to impose the temporal variation of light conditions upon the virtual object.

22. A method of creating a realistically lit virtual object comprising the steps of, the elements; and detecting light intensity with a plurality of spatially arranged light sensitive elements; transferring the output from each of the elements, or at least data corresponding thereto, to a computer; constructing virtual light conditions corresponding to that detected by imposing the virtual light conditions upon a virtual object.

23. A method according to claim 22 further comprising the steps of, recording the temporal variation of output from each element; constructing a virtual light condition which varies accordin 9 to the temporal variation in output from each element; and imposing the temporally varying condition upon an animated virtual object such that the lighting upon the object varies in accordance with variations detected by the elements.

24. A device substantially as hereinbefore described with reference to the accompanying drawings.

25- A lighting system substantially as hereinbefore described with reference to the accompanying drawings.

26. A method substantially as hereinbefore described with reference to the accompanying drawings.