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BACKGROUND OF THE INVENTION
This invention relates to computer image generation with topographical
response, and, more particularly, to computer image generation having the
capability to present images in real time that reflect relative motion
between a view-point and a simulated landscape or scene, wherein the
relative motion is not pre-programmed or canned, but is derived from
real-time sampling to determine the present interrelationship between the
view-point and the scene.
The images depict scenes that would be viewed by an operator or passenger
in a vehicle wherein the images reflect vehicle motion (pitch, roll and
yaw) as the vehicle interacts with the environment of the scene it is
traversing. In addition, the motion of a vehicle remote from a view-point
may be presented as it interacts with topographical features of the scene.
Computer image generation has been used for facilitating instruction and/or
training in the operation and control of a vehicle without need for
actually operating the vehicle. A typical configuration includes a model
or mock-up of an operator compartment having controls, monitors and status
displays like those encountered in an actual vehicle, along with a display
device for presenting images to the operator of scenes that would be
observed by a driver of the actual vehicle over a real landscape.
Prior vehicle models have been confined to operate through simulated
landscapes over predetermined paths, such as roads, bridges and highways,
with excursions therefrom limited. Typically there was no rolling terrain
so that the ground was flat, or for each place where the vehicle could be
in the data base describing the landscape, a slope of the terrain was
predeterminedly assigned. The first case over simplifies the simulation
for non-conventional vehicle movement and the second requires substantial
storage capability that may not be readily available or not feasible to
implement.
With increasing popularity of recreational (RV), off-road and all-terrain
vehicles, and the like, that are able to deviate from traditional vehicle
routes and to navigate over the landscape, it would be desirable to
present images in real-time that reflect the actual scenes that would be
viewed by an operator while taking non-conventional paths over the
landscape, wherein the freedom of choice of path is not restricted.
Further, it would be desirable to supply information relating to the type
of, or objects on, the terrain, such as asphalt, mud, rocks, boulders,
shrubbery, for determining vehicle interaction therewith both for adding
realism to the images presented, and for deriving audio cues, which are
especially effective for assisting operator training of land based
maneuvering.
Accordingly, it is an object of the present invention to present images
acurately representing actual scenes that would be observed by an operator
while directing a vehicle on non-conventional paths over the landscape
without having to actually operate the vehicle.
Another object is to provide audio cues to the operator that correspond to
real-time interaction between the vehicle and the landscape.
SUMMARY OF THE INVENTION
In accordance with the present invention, in a visual image generating
system for creating visual images from stored data, wherein a feature of
an image is defined by at least one polygon, a method for producing visual
images reflecting real-time interaction between a vehicle model and an
image to be displayed comprises sampling in real time the topography of
the image to be displayed in the vicinity of the vehicle model for
obtaining at least one sample indicative of the topography, determining
interaction between the topography of the image to be displayed and the
vehicle model in response to the at least one sample and modifying the
image to be displayed in response to the interaction determined. An audio
cue may be provided in response to a predetermined characteristic of the
at least one sample.
For obtaining the samples, plumb vectors having a predetermined
relationship to the vehicle may be used to determine a respective
intersection with a polygon in the vicinity of the vehicle. For example,
the plumb vectors may be referenced to respective range offset vectors
that pass through the centroid of the vehicle. The centroid may be further
referenced to a global or primary reference system.
The plumb vectors may be oriented forward the vehicle in the direction of
motion or may be positioned to sample directly under the vehicle if the
processing is rapid enough to present real time interaction between the
vehicle and the landscape. Freedom of choice of the path of the vehicle
over the terrain is not restricted.
When a plurality of sample points is obtained, interpolation among
predetermined sample points, some of which may have been previously
stored, is used to infer the contour, e.g. slope, of the topography prior
to determining interaction between the interpolated portion of the
topography of the image to be displayed and the vehicle model.
The features of the invention believed to be novel are set forth with
particularity in the appended claims. The invention itself, however, both
as to organization and method of operation, together with further object
and advantages thereof, may best be understood by reference to the
detailed description taken in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a view onto the side of a vehicle model and a schematic
representation of a sampling scheme in accordance with the present
invention.
FIG. 2 is a view onto the top of the vehicle model of FIG. 1.
FIG. 3 is a perspective view of a vehicle model and a schematic
representation of another sampling scheme in accordance with the present
invention.
FIG. 4 is a flow diagram of a method for sampling terrain in accordance
with the present invention.
FIG. 5 is a block diagram of a display system in accordance with the
present invention.
DETAILED DESCRIPTION
Referring to FIG. 1, a vehicle model 10, having a centroid faces 18 and 20
representative of the landscape in the area around vehicle 10. Polygons 18
and 20 abut along common edge 16 and do not lie in the same plane. Present
direction of motion for vehicle 10 is indicated by an arrow 25. A
positioning or range offset vector 30 that is fixed in relation to vehicle
10 extends from centroid 15 of vehicle 10 beyond the extremity of vehicle
10 in the general direction of arrow 25. Vector 30 includes a vector
component in the direction of arrow 25. A range, gravity or plumb vector
31 is directed toward the center of gravity of the earth from the end of
range offset vector 30. An extension of plumb vector 31 intersects polygon
20 at point 35 so that at least one sample point is obtained. Thus, the
distance from the end of vector 30 to polygon 20 at point 35, and the
location of point 35 in space, may be determined. Since range offset
vector 30 is fixed with respect to vehicle model 10, the distance from
vector 30 to polygon 20 along vector 31 is indicative of the contour of
polygon 20. The coordinates or vector location (with respect to the same
coordinate system used to define vector 31) of intersection point 35 may
be stored for subsequent processing.
Referring to FIG. 2, a view looking onto the top of vehicle 10 is shown. It
is noted that vector 30 further includes a lateral component so that
vector 30 extends beyond an extension of side 12 of vehicle 10. Additional
range offset vectors 32, 34 and 36 that are fixed with respect to vehicle
10 extend beyond vehicle 10 from centroid 15 in the general direction of
arrow 25. Vector 36 includes a lateral component so that vector 36 extends
beyond an extension of side 14 of vehicle 10. Vectors 32, 34 and 36 have a
respective plumb vector (not shown) associated therewith analogous to the
relationship between vector 30 and vector 31 (FIG. 1). An extension from
each of the respective plumb vectors (not shown) associated with vectors
32, 34 and 36 intersects face 20 at points 37, 38 and 39, respectively.
Thus, the distances along plumb vectors associated with vectors 32, 34 and
36 to points 37, 38 and 39, respectively, and/or the location of
intersection points 37 38 and 39 in space are indicative of the contour of
the polygon 20 analogous to range offset vector 30, plumb vector 31 and
polygon 20. The coordinates or vector location (with respect to the same
coordinate system as used for the plumb vectors) of intersection points
37, 38 and 39 may be stored for subsequent processing.
Also shown is a grid of prior sample groups 11, 13, 17 and 19, each having
a member corresponding to range offset vector 30, 32, 34 and 36. A
predetermined number of sample groups that form the grid may be stored in
memory for recall during processing of current samples 35, 37, 38 and 39,
so that an adequate number of sample points is available to provide an
accurate interpolation for inferring the contour and slope of the terrain
with which vehicle 10 is presently interacting. The earliest sampled
group, say group 19, may be eliminated from memory once vehicle 10 has
passed the area associated therewith.
The direction and positioning of range offset vectors 30, 32, 34 and 36 may
be modified to accommodate a change in direction 25 of vehicle 10. The
number of range offset vectors and splay between the outermost ones should
be selected so that the respective plumb vectors associated therewith
generate terrain samples such that the features and contour of the ground
over which vehicle 10 travels can be accurately determined from
interpolation of the samples. Typically samples 35, 37, 38 and 39 will be
taken at a predetermined instant resulting in discrete rather than
continuous samples. In accordance with the present invention, the values
of intersection or sample points 35, 37, 38 and 39 are interpolated along
with the values of predetermined samples from prior groups 11, 13, 17 and
19 to determine in real time the type and contour of the terrain that
vehicle 10 will next encounter if it continues moving in the direction of
arrow 25.
It is to be understood that in a real vehicle, drive means, such as a wheel
or tread, and guide means, such as runners (if used--e.g. snowmobile),
contact the ground and couple reactions between the vehicle and the
terrain. The type of drive and guide means, along with general
characteristics of the real vehicle, such as weight, stopping distance,
speed limitations and acceleration, are preidentified and incorporated
into vehicle model 10 and typically reside in a host computer system.
Criteria for determining the inverval between successive sample points
include the rate of change or gradient of the terrain, whether the vehicle
is turning and rate of turning, velocity of the vehicle, and character of
the terrain, such as roughness, uniformity, and composition, e.g. sand,
gravel, mud. As the velocity of vehicle model 10 increases, processing
demands typically increase since generally it is desired that the interval
between samples decrease for increasing velocity of vehicle 10.
Referring to FIG. 3, a schematic representation of another sampling scheme
in accordance with the present invention is shown. Range offset vectors
70, 72, 74 and 76 extend from centroid 15 of vehicle model 10 toward
respective extremities or corners of vehicle 10. Extending toward the
center of the earth from the end of each range offset vector 70, 72, 74
and 76 is a respective plumb vector 71, 73, 75 and 77. An extension of
plumb vectors 71 and 73 strikes polygon 20 at sample points 81 and 83,
respectively, and an extension of plumb vectors 75 and 77 strikes polygon
18 at sample points 85 and 87, respectively. Plumb vectors 71 and 77 may
be oriented to correspond to a position over vehicle propulsion means,
such as power driven wheels, of a real vehicle and/or over vehicle
traction means, such as undriven wheels, of a real vehicle that are
typically disposed along one side of vehicle 10, and plumb vectors 73 and
75 may be similarly oriented on the opposite side of vehicle 10. Plumb
vectors 71, 73, 75 and 77 thus sample terrain under vehicle 10.
In order to use the configuration shown and described with respect to FIG.
3, it is necessary that processing of data values from sample points 81,
83, 85 and 87 be rapid enough so that responses to the interaction between
vehicle 10 and the terrain represented by polygons 18 and 20 are
accurately reflected by updating the relationship between a display and a
viewpoint during each field cycle. In one common scheme related to a U.S.
television standard, two fields are interleaved to provide an updated
image thirty times a second. Thus, all processing for a field must be
completed within one-sixtieth of second, every sixtieth of a second.
Referring to FIG. 4, a flow diagram of a method useful with the present
invention is shown. A program begins at step 50 and executes step 52 to
sample at predetermined points the terrain represented by polygons in the
vicinity of a vehicle. The vehicle may be a simulated or model one which
an operator is maneuvering and controlling to travel through a data base
representative of a landscape, or it may be a vehicle remote from the view
point of an operator/observer.
Performance of step 54 stores the data obtained by sampling the terrain so
that it is available for further processing. The stored data forms a grid
of samples. As noted above, storing data is generally required when
sampling occurs in accordance with the configuration of the present
invention shown and described with respect to FIGS. 1 and 2. For the
configuration illustrated and set forth above with respect to FIG. 3, step
54 may be eliminated, if desired, and step 56 may be performed directly
after executing step 52.
In one type of computer image generation, a plurality of polygons having a
predetermined spatial relationship with respect to each other are used to
represent features and objects of a scene to be displayed. For example,
representation of a hill in a landscape may be implemented by arranging a
plurality of contiguous polygons whose size and slope piece-wise linearly
approximate the contour of the hill. Without more, the surface of the hill
would appear faceted due to the line visible at the juncture of polygons
having different slopes. The polygons may be textured and/or shaded for
camouflaging or hiding the lines at the abutment of neighboring polygons
and for suggesting to a viewer a contour or shape other than a basically
flat appearance available from an unmodified polygon. Polygon descriptors
are generally available from a data base which may be stored in a mass
storage medium such as magnetic disk or tape.
Execution of step 56 interpolates the transitions between sample data
points, both the current ones and predetermined ones from the stored grid,
for extrapolating or inferring the contour of the terrain defined by the
polygons from which the samples were obtained. Performance of step 58
determines the interaction between the topography of the terrain from
which the samples were obtained and the vehicle and orients the vehicle
model attitude and/or the visual display in response to the interpolated
values of polygon samples as the vehicle model moves through the data base
scene. The slope of the inferred contour of the terrain is used to
determine the roll, pitch and yaw components of the interaction between
the vehicle model and the terrain. The changes in roll, pitch and yaw that
are determined for the vehicle model are related to the dynamics of the
vehicle, e.g. pivot points, weight, inertia, so that unrealistic effects
are avoided.
Attitude of the vehicle model for reflecting real-time interaction may be
effected by different techniques depending on the type of display system
used. For a vehicle model depicted in a scene of a display and remote from
a view-point, the model is oriented with respect to its local landscape to
reflect real-time interaction between the vehicle and the local terrain.
For a display that presents what an operator/observer sees from a
view-point within the control station of a vehicle, an offset that
corresponds to the roll, pitch and yaw components of the real-time
interaction of the vehicle with its local terrain may be added to the
display so that the display reflects real-time interaction between the
vehicle and the local terrain.
In another display configuration, the control compartment for the
operator/observer may be supported so that it can move with respect to the
display. The roll, pitch and yaw components of the real-time interaction
of the vehicle with the local terrain of the data base are supplied to the
motion control system for the control compartment so that movement of the
control compartment may be modified to reflect the actual motion a vehicle
would experience while interacting with the landscape represented by the
data base.
Polygons may also be encoded with characteristics or attributes of the
terrain, such as mud, gravel and asphalt, so that the value of each sample
point of a polygon also includes an indication of the type of terrain.
This permits additional realism to be incorporated into the response of
the vehicle model and also enables generation of appropriate noise cues
corresponding to the part of the vehicle interacting with the attribute.
Execution of step 60 determines whether the vehicle has stopped. If it has
not stopped, then the program follows the N path and returns to perform
step 52. If the vehicle has stopped when step 60 is performed, then the
program proceeds along the Y path to execute step 62 which causes this
portion of the program to end.
Referring to FIG. 5, a block diagram of a display system in accordance with
the present invention is shown. A terrain sampler 120 has an input coupled
to an output of data base 110 for receiving descriptors of the polygons
that form the landscape over which a vehicle model can roam. Terrain
sampler 120 determines in real time the intersect points between plumb
vectors and the polygons as herein before explained. Intersect point
descriptors are provided to an output of terrain sampler 120 that is
connected to an input of sample processor 130.
Sample processor 130 acts on the data supplied thereto both for determining
the real-time roll, pitch and yaw components of the interaction between
the model vehicle and the landscape model base in response to distances
along plumb vectors, and for extracting terrain attribute information
therefrom.
Sample processor 130 includes a respective output coupled to a respective
input of a display control 140 and an audio generator 150. Display control
140 responds to the roll, pitch and yaw data provided thereto from sample
processor 130 for modifying the images to be displayed so that they
reflect the real-time interaction between the vehicle model and the
landscape with respect to a predetermined view-point. Audio generator 150
responds to the attributes of the terrain supplied thereto from sample
processor 130 for producing audio cues in response to the real-time
interaction between the vehicle model and the terrain.
In order to increase the efficiency and throughput of the system, data
transfers among data base 110, terrain sampler 120, sample processor 130,
display control 140 and audio generator 150 may be made along parallel
data paths as shown in FIG. 5.
In an alternative embodiment (not shown) the roll, pitch and yaw data from
sample processor 130 may be supplied to a motion control system for
controlling the motion of a moveable control compartment of a vehicle
model in response to the real time interaction between the vehicle model
and the landscape.
Thus has been illustrated and described apparatus and method for accurately
representing actual images that would be observed by an operator while
directing a vehicle on non-conventional paths over a landscape without
having to actually operate the vehicle. In addition, apparatus and method
for providing audio cues to the operator in response to real-time
interaction between the vehicle and the landscape have been shown and
described.
While only certain preferred features of the invention have been shown by
way of illustration, many modifications and changes will occur to those
skilled in the art. It is to be understood that the appended claims are
intended to cover all such modifications and changes as fall within the
true spirit and scope of the invention.
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