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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