Camera and Head Transformations

Introduction

In this document, we are going to talk about the purpose of Base Cam Transformation, Delta Cam Transformation and Delta Head Transformation found on several Control Board panels in camera compounds that can utilize camera tracking.

SCENE panel

When selecting the SCENE panel on the INPUTS Control Board, you can see that it has a Base Cam Transformation pin with 3D coordinates for position and rotation.

This parameter defines the shift between the virtual scene and the tracking systems' origin. Here, you can set where and how your scene is positioned.
If your model of the scene has the floor at 0 height, you should not change the Y coordinate, otherwise, you should set it to the same height as it is in the model. We recommend placing the floor at 0 height when creating the model, which makes using them more straightforward.
All the other coordinates can be freely changed to your liking, however, if the model is perpendicular to the floor - which is recommended - and the tracking system of your choice is well calibrated, changing the X and Z coordinates of the rotation is unnecessary.

STUDIO panel

Just as with the SCENE panel, by selecting the STUDIO panel you have a Base Cam Transformation pin, where you can set the position and rotation of the studio mask including the green screen mask. In other words, define the shift between the studio mask and the tracking systems' origin.

Here, most of the time, only rotating on the vertical axis (Y axis) is useful; in the case when the tracking system's coordinates are not perpendicular to the green screen.
Changing the Y position coordinate (height) of the studio should be done only in some special cases when the green screen is above or under the floor - e.g. it's on a platform or in a cavity. When the tracking system is correctly set up, the floor of the green screen is automatically placed at the real-world floor.
Changing the X or Z position coordinate is also something you should only do in some special cases. E.g. when the origin of the tracking system is out of range, you can move the green screen mask to the position of it's real-world counterpart. However, we strongly recommend moving the origin of the tracking system close to the green screen which makes using it more straightforward.

ORIGIN panels

Each camera input has its own ORIGIN panel with two user-customizable Transformation pins: Delta Cam Transf and Delta Head Transf. Furthermore, they have a Detect Origin button.

Delta Cam Transf

There are 3 different cases when the Delta Cam Transformation should be used:

• Since PTZ cameras don't provide data about their position, you can use this setting to place the camera in the virtual environment.
  • The PTZ rotation center height can be set in the Camera Calibrator.
    
    When this parameter is set and the corresponding CalibrationProfile is loaded in the Composer, the height is automatically loaded.
    Changing the Y axis' value in the Delta Cam Transf adds it to the value set in the Camera Calibrator - which is 0 cm by default.
  NOTE: One good practice when handling PTZ cameras is to dedicate a point as origin in the studio. This way, whenever the camera is moved, the distances can be measured from the same point and be inputted to the Delta Cam Transf.
  
• When there are multiple tracking systems are in use and their coordinate systems are different, setting the difference in the Delta Cam Transf allows for unifying their coordinate systems. E.g. when two coordinate systems are shifted 2 meters away on the X axis, setting 2 meters in the X axis of the Delta Cam Transf brings them to the same system. This way, when switching between tracking systems, the scene will be seen from the expected location. (See Detect Origin for an easier setup)
• When searching for issues, Delta Cam Transf can be used as a manual camera tracker. Changing the Delta Cam Transf values allows for simulating camera movements.

Detect Origin

You can define the origin of the virtual environment using an ArUco marker.
First, place an ID.70 (Generated from the 6X6 standard dictionary, you can generate it here https://chev.me/arucogen/. The size of the printed ArUco marker has to be 18 by 18 cm.) into the camera view, like so: 

By clicking on the trigger, Aximmetry will place the virtual environment's origin where the ArUco marker is placed, by changing the Delta Cam Transf property accordingly.

NOTE: Alternatively, you can download a pre-generated ArUco marker from here.

Delta Head Transf

Delta Head Transformation is the technical term for the vector between the center of the camera sensor and the tracking device.
If you have done a tracking calibration for your current setup of camera and tracking device, you should not change this as the CalibrationProfile set on the INPUT # panel already contains this information.
There are 2 cases when setting the Delta Head Transf is useful:

• You have no tracking calibration and want to set it manually
• The Delta Head Transformation changed on your setup, e.g. you moved your tracking device farther away from the camera sensor. You can set the difference between the two known positions here.

However, instead of changing the Delta Head Transf, we recommend using a CalibrationProfile where the tracking calibration is correct.

NOTE: The values set here are added to the one saved in the CalibrationProfile.