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Basic Calibrator
Camera Calibrator
Introduction
This document discusses setting up the inputs and the virtual scene to test a tracking calibration.
This document uses the AR_example compound file as a reference to demonstrate the test.
What is the AR_Example Compound?
AR_Example.xcomp is an Aximmetry compound created to demonstrate a simple AR scene. It also contains multiple AR elements designed for testing.
It is ideal to test your tracking system's accuracy, including the calibration of zoom, focus, lens distortion, center shift, etc., as being a simple scene, it is easy to check the tracking system's precision without any interference caused by other features.
This compound is part of the free Tutorial content package you can download from your my.aximmetry.com account.
If the Tutorial content package is installed on your computer, then you can find this compound here:
[Tutorials]:AR\AR_Example.xcomp
Setting Up the Inputs
To begin testing the tracking calibration, you'll need to complete the following steps:
- set up the video input,
- set up the tracking input (including the calibration profile, when applicable),
- adjust the tracking delay,
- set up the zoom device (when applicable),
- adjust the zoom delay (when applicable).
Setting Up the Video Input
Go to the INPUT # control panel in the INPUTS control board:
NOTE: The use of one input is enough for testing a single tracking system. The remaining inputs can be turned off.
On the INPUT # control panel's Pin Values, choose the video input source you want to use in the Camera Device dropbox menu. The Camera Mode is recommended to be set to AUTO Mode (default value), however, you can also manually specify the required frame rate and resolution if needed.
NOTE: If you have already mapped your video input device in the Startup Configuration window, then you can leave this parameter at Mapped: #1.
NOTE: The video input resolution and frame rate must match the Camera Mode's settings to receive the video input.
NOTE: The screenshot above represents Mapped: #1 set as the Camera Device since it is the default value set for the camera compound.
Setting Up Tracking Device
Still on the INPUT # control panel's Pin Value, set the Tracking Device and the Calibration Profile.
NOTE: If you have already mapped your tracking device in the Startup Configuration window, then you can leave this parameter at Mapped: #1.
NOTE: If you are using a tracking system with its own calibration solution, you must leave the Calibration Profile empty.
NOTE: If you are required, set the Zoom Device as well.
NOTE: The screenshot above represents Mapped: #1 set as the Tracking Device since it is the default value set for the camera compound.
Zoom Device
Zoom Device is a secondary tracking device that provides additional tracking data in combination with the Tracking Device. There are three use cases for this parameter:
- specifying third-party zoom encoder devices to receive additional lens data,
- specifying PTZ cameras' tracking data stream when PTZ cameras are tracked with additional tracking devices to determine their position,
- specifying the same tracking device that is specified at the Tracking Device parameter to be able to independently adjust the Tracking Delay and Zoom Delay parameters for it. (see later)
Adjusting the Delays
NOTE: To review what delay is in virtual production, please refer to the following entry:
Latency / Delay
Using Auto Delay
Starting from version 2023.2.0, Aximmetry is capable of automatically detecting the correct tracking (Detect Tracking Delay) and zoom delay (Detect Zoom Delay) values.
You can find these features among the INPUT # control panel's Pin Values:
To use it, you will need a red, blue, or green reference point in your studio. It could be any flat object or detail of even red, blue, or green color. In the example below, we chose a red circle as our target.
NOTE: It is recommended to use a flat target for reliable results.
NOTE: It is recommended to choose a color different from your background.
NOTE: It is recommended to use a higher shutter speed to avoid motion blur.
NOTE: It is recommended to place the target at a reasonable distance from the camera (avoid placing it too near, i.e. less than a meter away).
You may use one of these 3 images as reference points:
(Click on one of the 3 circles for the full-resolution image).
You can show the image on your smartphone or any other screen. Or print it out like in the example below.
Choose the color of the target in the Detect Target Color dropdown:
Switch On the detector you want to use. (Detect Tracking Delay or Detect Zoom Delay)
An instruction will appear. Follow the on-screen instructions:
After the target is detected by Aximmetry a new instruction appears depending on if you are making Tracking Delay detection or Zoom Delay detection:
When it detects the delay value, the following message appears, and the value of the delay will be set automatically for the corresponding pin:
Setting Up Delay Manually
You can set Tracking Delay and Zoom Delay in the INPUT # control panel's Pin Values. They use frames as the unit of measure.
NOTE: You can set any arbitrary value for the delays. When all input and output devices and the render engine run at the same frequency (recommended), then the value set will always be rounded to an integer value, according to the rule of mathematics.
To find the correct value pan the camera left and right - or zoom in and out if you are setting the zoom delay - and align the delay value manually until there is no difference in the camera's input picture and the virtual scene's movement.
Focus on the moments when the movement starts and ends for reference points.
Setting Up the Scene
On the INPUTS control board, select the SCENE control panel to adjust the Scene's position and orientation.
NOTE: In most cases, using the AR_Example.xcomp, adjusting the Scene's position and orientation are not necessary. In the rare cases where the tracking area is unusually large or distant from the tracking coordinate system's origin point, you'll likely need to adjust it.
The Scene's default position and orientation (Base Cam Transf pin values) are at the origin point (0, 0, 0 coordinates) of the tracking system's coordinate system:
If needed, you can manually adjust the position and rotation of the scene using the Base Cam Transformation parameters.
Base Cam Transformation
The Base Cam Transformation parameters allow for moving the virtual scene relative to the tracking device's coordinate system.
The Base Cam Transformation parameters are as follows:
Pos - Position, in order of appearance; these are the X, Y, and Z coordinates of the virtual scene. These parameters use meters for measurement.
Rot - Rotation, in order of appearance; these are the rX, rY, and rZ coordinates of the virtual scene. These parameters use degrees for measurement.
NOTE: You can learn more about Camera and Head Transformations here.
If the tracking system's ground level (0 height) and the studio environment's ground level (0 height) are at the same floor level, then do not adjust the Y parameter (which is the second box of the Pos row).
