VideoCAD

Camera Geometry

 Parameters

Parameters list

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Camera Geometry

 Parameters

Parameters list

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Camera Geometry

 Parameters

Parameters list

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Image sensor size

 

In the box, you can specify the size of the Image sensor or the size of Active area of the Image sensor.

 

See more: Image sensor and Active area of image sensor

 

The Image sensor size can be specified by any of the following ways:

 

Choosing a standard format (type) from the list 1/10",1/8",1/6",1/5",1/4.5",1/4",1/3.6",1/3.2",'1/3",'1/2.7",'1/2.5",1/2.3",1/2",1/1.8",1/1.7",1/1.6",2/3",1/1.2",1",4/3",1.5";

 

This traditional way of setting Image sensor size can be unaccurate for modern cameras.

 

Entering a custom format in inches, in the form of X/Y". For example: 1/7.31";

 

If you enter a format which does not exist in the list, the box turns yellow, and the Image sensor size will be calculated by VideoCAD.

 

Entering diagonal size of the image sensor in millimeters, in the form of dX.Y. For example: d6.0.

 

See more: Specifying image sensor size through its diagonal and aspect ratio

 

Entering sensor side sizes in millimeters horizontally and vertically separated by hash, in the form of W#H.  For example: 4.8#3.6;

 

See more: Direct specifying image sensor side sizes

 

After format or length of diagonal, separated by space character, you can specify the aspect ratio of the image sensor in the form of W:H. For example: 1/3" 16:9 or d6 16:9. If the aspect ratio of the image sensor is not specified, it is assumed equal to 4:3.

 

See more: Direct specifying active area size of the image sensor

 

Active area side sizes of the image sensor can be specified in millimeters horizontally and vertically separated by asterisk, in the form of W*H. For example: 4.8*3.6;

 

See more: Direct specifying active area side sizes of the image sensor

See also: Sensor and Lens>Image sensor, Specifying active area size of the image sensor/

 

When moving the cursor to the image sensor box the information on horizontal and vertical view angles of lens appears.

 

Changing the Image sensor size, and therefore the calculated values ​​of view angles of camera with enabled modeling lens distortion will lead to detuning parameters of distortion and warping view area form. To correct the mismatch you should set new values ​​of the actual view angles, taking into account the changed values ​​of calculated view angles.

 

Lens focal length

 

The values can be chosen from the list or typed by keyboard, e.g. when using the varifocal lenses.

 

Choose a value given in the lens specification in this box.

It is assumed that the lens format equal to or larger than the camera Image sensor format is used.

The lens focal length influences all the calculated parameters.

 

When moving the cursor to the lens focal length box the information on calculated view angles appears.

 

If in lens' specification there are view angles which are different from the calculated ones, then probably the lens has distortion. For precise modeling  such lens you should enable and adjust simulating distortion.

 

 

Focal length can be chosen from the list or typed into this box or duplicate boxes on the Tool bar of the Graphics window and on the 3D Video.

 

It is convenient to change lens focal length of active camera on layout in the Select/Edit mode, by moving grips at the corners of view area projection.

 

 

If a model is assigned to the camera, and the model has fixed focal length lens, then you can not change the focal length.

 

If a model is assigned to the camera, and the model has a lens with limited variable focal length, then you can change focal length within the limits only. When approach to the limit values, the box will become crimson.

 

You can change focal length in wide range of 0.5-1000mm of cameras, which have not assigned model or the assigned model have not specified limits of the lens focal length.

 

If the active camera is panoramic then the lens focal length box is colored by aqua-green.

 

Changing the lens focal length and therefore the calculated values ​​of view angles of camera with enabled modeling lens distortion will lead to detuning parameters of distortion and warping view area form. To correct the mismatch you should set new values ​​of the actual view angles, taking into account the changed values ​​of calculated view angles.

 

You can change lens focal length of all selected cameras simultaneously. For this purpose:

Select necessary cameras on the layout
Right click on this combo box, then click on the Assign to selected cameras pop up item.

 

See also: Sensor and Lens>Lens

 

Aspect ratio (of output image)

 

Aspect ratio of the output image of the camera: 4:3,16:9, 16:10 etc.

 

The Aspect ratio of the output image equals to the Aspect ratio of the active area of the image sensor and may be different from the Aspect ratio of the image sensor.

 

The Aspect ratio of the image sensor can be specified in the Image sensor size box.

 

See more: Specifying the Aspect ratio of output image

 

You can enter custom values ​​from keyboard in the form of <width> :<height>, for example 11:4.

 

By specifying formats 3:4 or 9:16, you can specify the so-called corridor format in which the height of the frame is larger than its width.

 

For correct simulation resolution in the corridor format you must also swap the number of pixels horizontally and vertically in the camera parameters and image processing settings.

 

 

Separated by space character after the Aspect ratio you can set the crop factor - the ratio of cropping active area size of the image sensor when the active area does not touch the edges of the image sensor. The Crop factor can be set as a vulgar fraction (separated by slash) or a real number. For example 4:3 0.67 or 16:9 720/1080. If the Crop factor is not specified, it is taken to be unity.

 

 

See more: Specifying the crop factor

 

If the camera has directly assigned active area sizes, then this box shows 'custom' and it becomes unavailable. To make it available, set the size of image sensor by any way except of direct specifying its active area size.

 

For correct calculation of person detection, identification and license plate reading areas and spatial resolution, after changing the Aspect ratio it is necessary to check and adjust vertical number of pixels in the Sensitivity and Resolution box and Image size on the Processing tab on the Image parameter panel.

 

Changing the aspect ratio and therefore the calculated value ​​of vertical view angle of camera with enabled modeling lens distortion will lead to detuning parameters of distortion and warping view area form. To correct the mismatch you should set new values ​​of the actual view angles, taking into account the changed values ​​of calculated view angles.

 

See also: Sensor and Lens>Image sensor's active area, Specifying active area size of the image sensor

 

Sensor and Lens

 

Clicking this button will open Sensor and Lens box. In the box it is possible to specify any image sensor size, active area size, specify lens distortion and adjust modeling active camera as a panoramic camera.

 

See more: Sensor and Lens, Specifying active area size of the image sensor

 

Height of installation

 

Height of installation can be chosen from the list or typed. The height of installation influences all calculated parameters.

 

In multi-level 3D projects, in 3D Video and 3D World, as well as in calculation of shadows, the height of installation,  heights of view area lower and upper bounds are calculated relative to the Base height

 

Height of installation can be negative.

 

Camera tilt angle

 

Camera tilt angle is a calculated parameter and can not be edited directly. The camera tilt angle is an angle between the main optical axis of camera lens and a horizontal.

 

Camera inclination is defined not by the tilt angle but by the three parameters:

 

 

Axial rotation angle

 

In the box you can specify the camera rotation angle around its main optical axis, in degrees.

The parameters in the Camera geometry box can not reflect the shape of view area rotated around its main optical axis, it is impossible to reflect changing projections under the influence of lens distortion. So the lens distortion and rotation around the axis within + -45 degrees does not affect the parameters. The parameters of the Camera geometry box continue to show values ​​as if the camera is not rotated.

 

When the rotation angle is more than 45 degrees, the parameters abruptly change their values to ones corresponded to the camera rotated on 90 degrees.

 

In this position the lateral faces of the view area will become the upper and lower faces, and upper and lower faces will become lateral ones.

 

When the rotation angle is more than 135 degrees, the parameters will reflect the initial position of the camera.

 

If a camera is rotated by an angle more than 45 degrees, when calculating person detection and identification, license plate reading areas,  the parameters: minimum vertical resolution (pixel/meter, pixel/ft), the minimum vertical size of face image ( pixels ), the minimum vertical size of license plate ( pix) are calculated based on the number of pixels along the horizontal, instead of the number of pixels along the vertical, as in this case the vertical side of the field of view is located along the horizontal.

 

When calculating the spatial resolution, rotation of the camera around its axis by default does not affect the position of the vertical and horizontal in the frame.  Horizontal and vertical positions are tied to the camera and not to the scene. You can change this rule, using the Spatial resolution and rotation checkbox in the Options box .

 

In the Graphics window, 3D Video and 3D world windows rotation of camera is displayed accurately. However, each passing through a multiple of 45 degrees angle, camera tilt angle is changed so as to keep the values of the View area upper bound height and the View area upper bound distance, taking into account the fact that a view area face appeared on top, becomes the upper bound of the view area.

 

When you rotate the camera around its axis the view area projection changes its shape, sometimes becomes infinite. To limit the distance of drawing view area, use the Maximum distance of drawing view area.

 

For a fuller picture of rotated view area projections it is recommended to set the Level 2 in pop up menu of the View area projection bounds and Shadow buttons.

 

See also: Using camera rotation around its own axis

 

Base height

 

The base height allows to change the height of installation of the camera together with heights of lower and upper bounds of its view area and the other heights. These heights are calculated relative to the base height. Therefore, changing the base height does not affect the other parameters in the the Camera geometry box.

 

Changing the base height can be represented as lifting or lowering the camera from floor to floor with all the other parameters.

 

 

 

The base height affects the position of the camera along the vertical, relative to other cameras and constructions in the 3D Video and 3D World windows, as well as in the calculation of shadows in the Graphics window.

 

At the time of placing a new camera or pasting copied camera, its base height is automatically set equals to the base height of the active layer .

 

Height of criteria of person detection and person identification, license plate reading are considered relative to the base height of the camera, which the projections of identification, detection, license plate reading  areas belong to.

 

The base height is calculated relative to the Zero ground and can be negative .

 

See also: Working with layers and multi-level projects, Layers>Height

 

 

View area upper bound height

 

The height of view area upper bound can be chosen from the list or typed. In the horizontal projection of the calculated view area the space above the upper bound height is not taken into consideration.

 

Together with view area upper bound distance it completely determines a camera tilt angle and all calculated parameters through it.

 

 

 

The height of view area upper bound influences the projections of the person detection, identification and the license plate reading areas only through changing the camera tilt angle. The individual values of lower and upper bounds are customized in these projections' calculation criteria. For instance, when identifying a person the default lower bound is 1.5 m and the upper one is 2.2 m.

 

In multi-level 3D projects, in 3D Video and 3D World, as well as in calculation of shadows, the height of installation,  heights of view area lower and upper bounds are calculated relative to the Base height

 

Height of view area upper bound can be negative.

 

       Height of calculating Spatial resolution, Shadows and Depth of Field

 

Heights of the upper and lower bounds of view area are taken into account when calculating shadows. If in the menu of the Shadow tool Within projection is chosen, then a point in the horizontal projection is considered as shaded if at least partially shaded the vertical segment, formed by this point in the altitude range from the view area lower bound height to the view area upper bound height.

 

If in the menu of the Shadow tool 2 levels is chosen, then the 2 sections of the view area by 2 horizontal planes are simultaneously shown, located on the height of lower and upper bounds of the view area. From the sections subtract shadows from obstacles

 

If in the Height box of the Depth of field box, AUTO is chosen, then calculation of depth of field in the horizontal projection is carried out at the middle height between the heights of the view area lower bound and the view area upper bound.

 

If in the Height box of the Spatial resolution box, AUTO is chosen and in the View area projection bounds and Shadow buttons the Within projection is chosen, then calculation of spatial resolution in the horizontal projection is carried out at the middle height between the heights of the view area lower bound and the view area upper bound.

 

If in the Height box of the Spatial resolution box, AUTO is chosen and in the View area projection bounds and Shadow buttons the 2 levels is chosen, then calculation of spatial resolution in the horizontal projection is carried out at the height of the view area lower bound.

 

View area lower bound height

 

The height of view area lower bound can be chosen from the list or typed. In the horizontal projection of the calculated view area the space below the lower bound height is not taken into consideration.

 

The height of view area lower bound influences the following calculated parameters:

 

 

 

The height of view area lower bound doesn't influence the projections of the person detection, identification and license plate reading areas. The individual values of lower and upper bounds are customized in these projections calculation criteria. For instance, when identifying a person the default lower bound is 1.5 m and the upper one is 2.2 m.

 

In multi-level 3D projects, in 3D Video and 3D World, as well as in calculation of shadows, the height of installation,  heights of view area lower and upper bounds are calculated relative to the Base height

 

Height of view area lower bound can be negative.

 

       Height of calculating Spatial resolution, Shadows and Depth of Field

 

Heights of the upper and lower bounds of view area are taken into account when calculating shadows. If in the menu of the Shadow tool Within projection is chosen, then a point in the horizontal projection is considered as shaded if at least partially shaded the vertical segment, formed by this point in the altitude range from the view area lower bound height to the view area upper bound height.

 

If in the menu of the Shadow tool 2 levels is chosen, then the 2 sections of the view area by 2 horizontal planes are simultaneously shown, located on the height of lower and upper bounds of the view area. From the sections subtract shadows from obstacles

 

If in the Height box of the Depth of field box, AUTO is chosen, then calculation of depth of field in the horizontal projection is carried out at the middle height between the heights of the view area lower bound and the view area upper bound.

 

If in the Height box of the Spatial resolution box, AUTO is chosen and in the View area projection bounds and Shadow buttons the Within projection is chosen, then calculation of spatial resolution in the horizontal projection is carried out at the middle height between the heights of the view area lower bound and the view area upper bound.

 

If in the Height box of the Spatial resolution box, AUTO is chosen and in the View area projection bounds and Shadow buttons the 2 levels is chosen, then calculation of spatial resolution in the horizontal projection is carried out at the height of the view area lower bound.

 

View area upper bound distance

 

Together with the height of view area upper bound, the view area upper bound distance completely determines the camera tilt angle and all the calculated parameters via it.

 

 

When the camera is located above the view area upper bound, a view area upper bound distance is the maximal distance of surveillance. The view area upper bound distance is chosen from the list or typed. The view area is calculated up to this distance.

 

 

When the camera is located below the view area upper bound, the view area upper bound distance can become the minimal distance of surveillance.

 

 

When a camera is located above the view area upper bound, a view area upper bound distance is the maximal distance of surveillance. The view area upper bound distance is chosen from the list or typed. The view areas are calculated up to this distance. Together with the height of view area upper bound, the view area upper bound distance completely determines the camera tilt angle and all the calculated parameters through it.

 

The view area upper bound distance influences the projections of the person detection, identification and the license plate reading areas only through changing the camera tilt angle. The maximal distances of the person detection, identification and the license plate reading can differ from the lower and upper bounds distance both to a smaller or larger extent.

 

When you rotate the camera around its axis, each pass through a multiple of 45 degrees angle, the camera tilt angle is changed so that a view area face appearing on top, becomes the view area upper bound.

 

See also: Maximum distance of drawing view area

 

View area lower bound distance

 

The view area lower bound distance is a calculated parameter and can not be edited.

 

When the camera is located above the view area upper bound, the view area lower bound distance is the minimal distance of surveillance (dead zone of surveillance).

 

 

When the camera is located below the view area upper bound, in some positions the view area lower bound distance is the minimal distance of surveillance too.

 

 

In some positions the view area lower bound distance can be the maximal distance of surveillance.

 

 

The view area lower bound distance can be negative.

 

 

The view area lower bound distance doesn't influence the person detection, identification and the license plate reading area projections. The minimal distances of the person detection, identification and the license plate reading can differ from the lower and upper bounds' distance both to a smaller or larger extent.

 

This parameter reflects the correct value only if:

Camera is not rotated around its axis or the rotation angle is multiple of 90 degrees;
Lens distortion is not considered.

In other cases, the projection of view area has a more complicated form and displayed graphically in the Graphics window.

 

View area projection length

 

The view area projection length is a calculated parameter and can not be edited.

 

When there is an actual view area projection, the view area projection length displays the absolute value of difference between the upper and the lower bound distances of view area projection.

 

When there is no actual view area projection, the parameter doesn't have any sense and is not displayed. The parameter displaying enhances the convenience in use when it is required to obtain the length of view area projection.

 

This parameter reflects the correct value only if:

Camera is not rotated around its axis or the rotation angle is multiple of 90 degrees;
Lens distortion is not considered.

In other cases, the projection of view area has a more complicated form and displayed graphically in the Graphics window.

 

 

Width of view area projection upper bound

 

The width of view area projection upper bound is a calculated parameter and can not be edited.

 

According to the "Projection" switcher state the width of view area projection upper bound displays the camera view area width at the point of intersection between the camera view area bound and the view area projection upper bound, or the view area projection edge width between the lower bound and the upper one.

 

This parameter reflects the correct value only if:

Camera is not rotated around its axis or the rotation angle is multiple of 90 degrees;
Lens distortion is not considered.

In other cases, the projection of view area has a more complicated form and displayed graphically in the Graphics window.

 

 

Width of view area projection lower bound

 

The width of view area projection lower bound is a calculated parameter and can not be edited.

 

According to the "Projection" switcher state the width of view area projection lower bound displays the camera view area width at the intersection point between the camera view area bound and the view area projection lower bound, or the view area projection edge width between the lower bound and the upper one.

 

This parameter reflects the correct value only if:

Camera is not rotated around its axis or the rotation angle is multiple of 90 degrees;
Lens distortion is not considered.

In other cases, the projection of view area has a more complicated form and displayed graphically in the Graphics window.

 

 

 

Projection

 

A "Projection" is a switcher determining a way of calculation:

 

The view area lower bound distance and the view area lower bound width when the view area is narrowing upwards on the view area lower bound distance;
The view area upper bound distance and the view area upper bound width when the view area is narrowing downwards on the view area upper bound distance;

 

When the switcher is checked, the view area bound distance and width are calculated according to narrower level of the view area opposite bound. In this case all the points of the calculated view area horizontal projection from the lower bound up to the upper one hit in the camera view area.

 

When the switcher is not checked, the distance up to the camera view area bound intersection with the upper or lower bounds and the width of this bound are calculated.

 

When the view area is not narrowing towards the opposite bound, the switcher doesn't have any sense and is not displayed.

 

Maximum distance of drawing view area

 

Value in this combo box limits the distance from the camera beyond which the view area is not drawn in the Graphics window and in the 3D World.

 

This tool is particularly useful for simulating camera rotation around its axis and lens distortion.

 

If the value in this box is less than the maximum of the view area upper bound distance and the view area lower bound distance, the box is colored in pink color.

 

 

 

External link: "The principles of CCTV design in VideoCAD. Part I. Camera view area"(*.pdf).