Parameter Pool

All parameters are collected in the parameter pool. In the parameter pool, you find every encoder or optical tracked value.

Pivot Rotation

Rotates the coordinate system of a rig around a free definable point in space. The camera Rig is bound to the pivot point in a parent-child relationship.

PivotX, PivotY and PivotZ define the location of where the rotation takes place. Rotation specifies the rotation in degrees around the Y Axis of the pivot point.

After the rotation, the coordinate system of the Rig is rotated around the Pivot Point. This is useful if, for example, a rail tracker needs to be adjusted in angle and offset to a studio coordinate system.

Location Pivot Rotation

The location pivot rotation rig is similar to the Pivot Rotation. The difference is that this rig takes the pivot point coordinates from the child camera’s position offset, which is attached to the camera position. This rig accepts only a rotation angle, as the position is taken from the child position offsets.

Arm Rig

The Arm rig is mainly used for Spidercam setup, or anywhere a mounted arm follows a rotation axis. The rig does not include any head length or angle adjustments to the next child. All rotations that go into the Tilt, Pan and Roll axis are given to the next sibling. It is possible to set JointX, JointY and JointZ values to adjust mounting offsets between the position giving element and the arm.

The arm length coordinates define the direction and length of the arm.

Translation

The Translation rig is mostly used as parent rig to an Arm or CraneArm Rig. It lets you modify the position of all child rigs. PosX, PosY and PosZ can be used to track the position. It is a usual element in a Spidercam setup.

Crane Arm

The Crane Arm rig is used to represent a crane arm. The difference from the normal Arm Rig is that the direction fields define a normalized direction of the arm, and the length is defined by the ArmLength field. In the arm rig, the Length parameters can be separated by axis.

You can set JointX, JointY and JointZ values to adjust mounting offsets between the position giving element and the arm.

ArmdirectionX, ArmdirectionY and ArmdirectionZ are normalized to 1 and define the initial direction of the Arm. Usually, ArmdirectionZ is set to -1.

Crane Head

A Crane Head represents a perpendicular element, which can be attached to a crane arm, or to a simple arm. The Headlength defines the horizontal length in -Z direction after the perpendicular element. The Headheight defines the Height in -Y direction after the perpendicular element.

Lens File

The Lens File rig must always be the first in a rig hierarchy. It is able to select one of the lens files, which must be located in the Lensfile folder in the Tracking Hub configuration folder in %ProgramData%. Once in the hierarchy, the lens file interprets the incoming raw zoom and raw focus values and sends FieldOfView, K1, K2, CenterShift and NodalPoint to the engine. The camera service object must be targeted to the lens file rig.

The only trackable parameter in the rig is the lensext parameter. In some protocols, such as FreeD, the lens extender is tracked. The value of lensext can be 0 or 1. If it is 0, the first lens file is used. If set to 1, the second lens file is used. The scaling values define a scale factor for the field of view with respect to the actual zoom value. ScYNear and ScXNear are the scaling factor when the lens is completely zoomed in. ScYWide and ScXWide define the scaling factor when the lens is completely wide. Between Wide and Near, the values are interpolated. If you do any changes inside the lens file or add some new, you must press Reload to make them available in your configuration.

Camera Rig

The Camera Rig represents the simplest camera known in the Tracking Hub. It holds the rotation and position parameters of a real camera in the studio. Zoom and Focus (in raw format coming from an encoder) and the Front, Height and Right lens shifts which are coming from the mount of the camera.

CameraFD Rig

The CameraFD Rig is similar to the standard camera, but with special developments for the Spidercam fielddolly (FD) and a changed rotation order ( X Z Y ).

Position and Rotation

Tilt, Pan and Roll defining the rotation of the camera around the X,Y and Z Axis. PosX, PosY and PosZ define the position of the camera in space. Each of these values might be tracked. In the case of a Pan/Tilt camera head which does not provide position information, the position can be adjusted in the offset values.

Zoom and Focus

Zoom and Focus come from the Lens encoders (whether internal or external). In the system and in Viz Engine, these values are always normalized and go from 0 to 1. Therefore, it is most important that the Lens Ranges are calibrated correctly in the tracking system.

Center Shift

Whenever you mount a lens to a camera body, the connection is never 100% the same every time; hence, there is always an offset between the camera body and the lens which shifts the angle of the light onto to charge-coupled device (CCD). In the Viz Virtual Studio software, this effect is called the Center Shift.

Note that every lens shows its own center shift and can for the most part be ignored as it is much smaller than the center shift caused when mounting the lens to the camera body. The most visible center shift is caused by the actual mounting of the lens and is more and more visible as the mount connection between the camera body and the lens becomes damaged/worn.

In order to calibrate the center shift, the Camera Rig handles the CenterX and CenterY offsets the following way: Completely zoomed out the full offset is applied and sent to Viz Engine. When zooming in, these values go in the zero direction until they reach absolute zero (completely zoomed in). It is absolutely necessary to calibrate this center-shift to get an acceptable tracking result. Whenever you see a movement of virtual objects when zooming in and out, you need to check if the center shift has changed.

To calibrate the center shift, follow the algorithm below:

1. Reset the CenterX and CenterY values to zero.

2. Look for a corner or easy to identify point in the camera view.

3. Enable the Center Shift Cross in Viz Artist, see Scene Settings > Virtual Studio.

4. Zoom in completely to this point and adjust focus. This is also a good point in time to check the back focus of the camera.

5. Pan and tilt the camera until the corner or point aligns with the Center Shift Cross.

6. Zoom out completely and see that the point slides away from the center.

7. Adjust the CenterX and CenterY values until the corner or point aligns with the Center Shift Cross again.

8. Zoom out completely. If the Center Shift Cross is no longer in the corner or point, repeat from step 5.

   Note: Repeat the steps until the Center Shift Cross is on the corner or point at all times. After two or three iterations, this is usually the case.

Mounting Offsets

In order to get an acceptable result, we need to know the exact position of the camera’s charge-coupled device (CCD) position. The CCD is (after the optical nodal point) the position of the Viz Engine remote camera. Not every tracking system gives that position. More likely, the position of the last rotation axis on the mechanical head is given, which in most cases is the tilt axis. If the send position is not clear, you need to contact the vendor of the tracking system.

After mounting a camera to a head, there are always offsets between the tracked point and the CCD of the camera. Many cameras have a mark on their body which marks the position of the CCD. If no mark is visible, you can assume that the CCD is 2 cm behind the mounting point of the lens.

In Tracking Hub, we know three mounting offsets. The FrontLensShift, HeightLensShift and the RightLensShift. The following drawings show the Front and Height Lens Shift and how these values change the behavior of the CCD.

Extended Lens Parameters Rig

The Extended Lens Parameters rig holds parameters which are rarely used and delivered by TrackMen and Libero only.

Object Rig

The Object rig is used to position an object in Viz Engine with the use of shared memory and the object service. It can be used to mask out pedestals, which would be in view of other cameras or to track objects with the Motion Analysis tracking system. Pan/Tilt/Roll are the rotation angles of the object and PosX, PosY and PosZ are the position in centimeters (cm). Connected to an Object-Service the coordinates are sent to Viz Engine and can be applied to any objects in the Viz Artist scene tree by a script.

Nodal Point

Let us assume the OpenGL camera is placed on the charge-coupled device (CCD) of the camera body. In the image, above, it completely depends on the field of view, where the light rays reflected from an object conjure to a point and create a sharp picture on the CCD. For sports, where the real camera is far away from the observed objects (we assume distances of more than ten meters), there is no influence from the adjusted focus. Therefore, in the image above we only observe the zoom effects on the nodal point of the objects watched.

Zooming in and out, causes the light rays, going through the lens, to conjure on a moving point behind the lens. In our Viz Virtual Studio software, we call this point the Nodal Point, and this point marks the position where we have to place our idealized OpenGL camera. The Nodal Point is defined during lens calibration, which is still happening in the Viz Engine. Therefore it is not an error, if you zoom in and out, and the position of the camera is moving towards and away from the Look-At direction of the camera. This is intended and must be done to provide an accurate result.

Center Shift

Whenever one object is mounted to another, the connection is not 100% straight. This is true for camera bodies and lenses as well. There is always an offset angle between the camera body and the lens. Therefore, the light does not come completely straight to the CCD. In the Viz Virtual Studio software this effect is called the Center Shift. Every lens shows its own center shift, which is much smaller than the mount error center shift and can be ignored most of the time. The most visible Center Shift is caused by the mount and becomes more and more visible/evident as the mount connection between the camera body and the lens becomes damaged.

Mounting Offsets