Image Tracking

Image tracking is a great way to attach responsive content to a physical object or anchor your scene to a known location in the real world environment. With Torch, you can set up images to be tracked completely within our visual design environment. 

Managing Tracked Images

Due to limitations in processing power, there is a maximum of two continuously tracked images allowed per scene. Only one image may serve as a scene anchor for a given scene. Both images may be used to trigger interactions. Management of these images is done in the Scene Options Drawer. 

  1. Tap the Scene Pill at the top of the screen of the Design Environment.
  2. Tap “Tracked Images”
  3. Tap “Add Tracked Image”
  4. Select an image to be tracked either from "This Project," "Camera Roll," "Browse," or "My Projects."
  5. Once the upload is complete, tap the image to bring up the Image Settings.
    1. Physical Width is used to determine how far away the tracked image is away from the phone. We find tracking performance is best with images that are 5 inches (12.5cm) or wider. An incorrect Physical Width value will not break image tracking, but will result in an incorrect position in the physical space, causing scene objects to appear larger or smaller.
    2. Image Orientation is used to decide whether to display the placeholder version of the tracked image horizontally (on a floor) or vertically (on a wall). In design mode, a digital copy of the tracked image is displayed over the real image to ensure tracking is working properly. This stand-in image also allows authoring without the tracked image being available. Please note: this stand-in image is not displayed in play mode.
  6. Tap the check mark in the lower right to save your changes.

Anchoring a Scene to a Tracked Image

By default, a scene uses the World Anchor as the anchor point for the scene content. Instead, you can specify for the scene to anchor to one tracked image per scene. This will cause the content of the scene to stay relatively positioned to the real world image even if it moves around. This setting is managed in the Scene Options Drawer. 

  1. Tap the Scene Pill at the top of the screen of the Design Environment.
  2. Tap “Anchor”
  3. Tap “Tracked Image”
  4. Select the image to use as an anchor.
  5. Upon selection, the placeholder image will immediately appear. If the real world image is not found, the placeholder will appear at the World Anchor with the orientation specified when the tracked image was configured.

Detecting Tracked Images Found or Lost

You can respond to a tracked image being found or lost using Scene Interactions. These interactions work just like Object Interactions but have a different set of triggers. Scene interactions are managed in the Scene Options Drawer.

  1. Tap the Scene Pill at the top of the screen of the Design Environment.
  2. Tap “Interactions”
  3. Tap “Add Interaction”

NOTE: an "Image Lost" trigger will not fire unless the tracked image has been found either through an "Image Found" interaction or a Scene Anchor using a Tracked Image.

Image Tracking Tips

  • We have found wider than 5” or 12.5cm (0.125m) is best.
  • The best images have a lot of colors and contrast. They do not need to be complex.
  • When the physical image leaves the view of the camera, the scene anchor will “stick” to the last known location of the physical image.
  • Environment lighting can affect tracking performance.
  • Moving the device around a fixed physical image performs better than holding the device fixed and moving the image in front of the camera.
  • Taking photos of the image to be tracked works really well. You can even take photos of slightly irregular surfaces. Just ensure the image is cropped to eliminate any visual information that may not be reliably detectable. 
  • We have good luck using the iOS "Measure" app which uses AR to measure the width of a physical object.
  • Using pure digital files as the tracking reference is not always best due to differences caused in printing/producing the physical image. For example, when tracking a movie poster it may be better to take a photo of the physical poster as the tracked image reference rather than uploading the digital art file used to create the poster. 

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