Registering digital content accurately against the real world environment is a key challenge when developing for optical see-through devices. This is due to the differences in facial geometry and visual acuity among end users. The spatial and optical relationships between the user's eyes and the displays will be slightly different for every user.
A personalized calibration profile enables the Vuforia SDK to position content accurately for a user's unique visual perspective when wearing the device. This is why calibration is recommended for all users and especially those who wear glasses or contact lenses.
Using the Calibration Assistant
Follow these steps to load the Vuforia Calibration assistant and generate a custom calibration profile to use with your digital eyewear apps. During this process, you should position the headset so that it is comfortable and the display area is centered in their field of view. You should also be wearing any corrective lenses that you will normally wear when using a digital eyewear device. It is important that the calibration measurements reflect conditions that are consistent with how you will see things when using the device.
Calibration Assistant Intro Screen
- Download the Vuforia Calibration Assistant and install it on your digital eyewear device.
See: How To install an APK using ADB.
- Download and print the calibration target. This target must be printed at its native A4 letter size.
- Tape the target to a wall so that the center of the target is at eye level when you look straight ahead.
- Put the eyewear on, center the display within your field of view.
- Launch the Calibration Assistant.
- Create a new profile
- You will be presented with a sequence of instruction screens that will guide you through the calibration process.
During calibration, you will be closing one eye and aligning a red rectangle to the edges of the stones image by moving either forwards or backwards. You will do this two times for each eye - once near the target and again farther away.
Near Target Registration
If you see that the rectangle is larger than the target, move forwards until the red rectangle fits on the image.
Far Target Registration
When the edges are aligned, press the control button to capture the calibration measurement.
After performing the near and far registration steps for each eye, you will be asked to verify that the resulting calibration is accurate by evaluating the static registration of the augmentation on the target. Static registration is a measure of how accurately the position of the target is estimated from a static position. Static registration is distinct from dynamic registration, which occurs when the target is tracked with motion. This is why it's important to hold still while evaluating static registration.
To evaluate static registration performance:
- View the target from multiple perspectives
- Pause in each perspective and observe how accurately the augmentation is scaled and positioned on the target.
- It is important that you perform this step without moving your head or body
- Save and name the profile if you are satisfied with the results. If not, recalibrate the device.
|Save or Recalibrate||Name a saved calibration profile|
Using Calibration Profiles
Calibration profiles are stored in a shared location on the device where they can be accessed by any other Vuforia digital eyewear app installed on that device. The SDK provides an Eyewear API for selecting and activating user calibration profiles programmatically. This enables developers to provide users with the ability to select which profile to use from within their app. If a custom profile isn't selected, the SDK will use the last active profile by default. See the Digital Eyewear samples to see how to load profiles by their profile number.
To remove a calibration profile, select the profile in the Profiles screen and press the garbage can icon. You will be asked to confirm that you want to delete that profile.