CCTV design in VideoCAD. Camera view area


Hello! In this lesson we will consider the most important
concepts of VideoCAD software. These are:
Camera view area and
Horizontal projection of the view area View area – is a three-dimensional geometrical
pyramid-shaped figure with the vertex, starting from the camera lens View area is in the shape of a regular pyramid
only if the lens focal length more than 3-4 millimeters. In case of short-focus lens the actual shape
of view area is different from the pyramid because of influence of lens distortion
Any object inside the view area will be visible on the screen, when it is not shaded by other
objects Objects outside the view area will not be
visible Object that gets into the view area partially
will be visible partially View area can be infinite View area may be limited by the ground or
by other obstacles Look at limiting view area by walls with door
and window openings View area minus shading from environment obstacles
(these are uncontrolled zones) is called in VideoCAD the control area
It is important to understand that the View area and Control area are complex three-dimensional
shapes. They can be fully represented only in three
dimension But designing and making documentation is
more convenient in 2D projection The transition to two-dimensional is possible,
only when the camera observes objects on the ground or other horizontal plane. However, this condition is satisfied in most
real tasks of video surveillance To work in 2D VideoCAD constructs horizontal
projections of the view areas Let’s consider the principles of construction
of these projections To construct the projection it is necessary
to specify a range of heights that must be controlled by the camera
For example, to monitor people do not try to hide from surveillance it is sufficient
to set range of heights from one to two meters In this case, faces of people with height
from 1.2 to 2 meters get into the range of heights of 1-2 meters Here we can see that the near bound of the
view area projection limits visibility of an object of minimum height. The far bound of the projection limits visibility
of an object of maximum height Hide vertical projection and move to the horizontal
projection Let’s place 3D models of the maximum height
of two meters on the bounds of the horizontal projection of view area Then we will watch on the screen how the model
will look Now, place on the near bound of the projection
3D models of people of 1.2 meters, that is the minimum height We can see our view area in 3D with our three-dimensional
objects We see, face of person of minimum height is
seen on the screen when the person is farther than the near bound of projection, within
the projection Face of person is not seen on the screen when
the person is nearer than the near bound of view area projection Thus, the near bound of projection limits
visibility of faces of people of minimum height The side bounds of projection limit visibility
of faces of people of maximum height If an object is outside the projection, his
face gets out of view area and thus disappears from the screen The far bound of view area projection limits
visibility of faces of people of maximum height too So if a high model is farther than the far
bound, its head does not get on the screen wholly Thus, we see important principle of constructing
horizontal projection of view area in VideoCAD: Any point located within the horizontal projection
of view area on the plane and within the predetermined height range vertically will get into the
view area Here the view area implies a three-dimensional
object. If this point is not shadowed, it will be
visible on the screen. We have considered only one of eight possible
positions of the camera Let’s check constructing the view area projection
in a different position when camera height is less than the maximum height of surveillance In this position, view area becomes infinite Set camera height less than the maximum height
of surveillance Then by the same way move the 3D model along
the near border of the view area projection, watching visibility of the head of the model
on the monitor. We see that in this camera position near border
limits the visibility of high model. For the rest, the principle is valid. Actually, the principle of construction of
the view area horizontal projection is valid in all camera positions Enable modeling lens distortion Rotate the camera around its axis Shape of view area and its projection becomes
more complicated Move the 3D model of minimum height along
the border of the projection, watching visibility of the head of the model on the monitor If the model is within the projection, head
of the model is visible on the monitor The head of model outside the projection disappears
from the monitor So, the principle of construction of view
area horizontal projection is valid in modeling lens distortion and camera rotation around
its axis Let’s disable modeling lens distortion and
camera rotation around its axis Place in the view area a shading object We can see how it looks in 3D. We will use a two-dimensional projection and
the image on the monitor Move the 3D model along the border of the
shadow, watching visibility of the head of the model on the monitor We see that if the model is within the horizontal
projection of control area, then its head is visible. If the model gets into the shading, then its
head disappears from the screen The principle of construction of control area
horizontal projection is valid in modeling shading In any case VideoCAD constructs horizontal
projection of view area and control area so that if an object is within the projection
on plane and within a predetermined height range, then it gets into the view area That is, if an object is located on the projection
then it will be visible. This is very important principle of constructing
projections, which allows using the horizontal projections in designing The basis of design in VideoCAD is work with
the horizontal projections of view areas on layout The layout might be supplemented by graphics
background and additional constructions For this purpose VideoCAD offers many useful
tools The layout might be supplemented by 3D models
from the VideoCAD library If necessary, we can import additional 3D
models from the open Google 3D warehouse We can move the camera and rotate it in all
planes We can change lens focal length and view angles
by moving grips on the projection We can change camera parameters and position. For example, height… Angle of rotation around its axis. And other parameters.. See 3D model of image from the camera We can see the full 3D representation of the
view area. It is particularly important in cases where
2D projection is not enough In three-dimensional view, we can consider
every detail. We can look inside the view area Consider its intersection with furniture,
models… See what resolution it intersects… Finally, let’s consider an example of a
complex view area constructed with taking into account the lens distortion We see the distribution of the spatial resolution
… Shading … Rotation of the camera around its axis … We can also look inside the view area … Look out from the view area … So, this lesson is over. Thank you for attention!

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