UX Concepts and their application
Ground Plane relies on visual details in the environment to detect and track planes, as well as the user's position in the world. A Surface Indicator is a valuable UI tool to inform users of where and when they can place content in their setting. The Vuforia Ground Plane samples demonstrate the use of a Surface Indicator and show how to change its presentation to reflect surface conditions.
Surface Indicators can support multiple modes of content placement - whether content should be placed automatically in response to a user event, or interactively where a user selects to place that content.
The Smart Terrain Tracker performs 'hit tests' to find Surfaces in the world. Hit testing is accomplished by projecting (casting) a virtual ray into the world, at a specific location, to identify whether it intersects with a surface. The result (test) indicates whether a surface has been found and where it is. Hit testing informs the Surface Indicator by providing results indicating the presence and location of surfaces.
On devices where supported hit tests take detected horizontal surfaces into account. On all other devices a plane is defined using an expected device height provided via API and the device's sensors.
- Automatic hit testing - hit tests are performed repeatedly at short intervals against the area in the center of the camera view. This occurs automatically so that users don't have to select surfaces manually. The Automatic UX Mode provides the easiest UX for users to understand.
- Interactive hit testing - hit tests are performed against the area that a user selects on their device screen. This provides more flexibility for content placement but requires that users understand which surfaces can be supported.
- Mid-air content positioning - content can be placed at a defined position relative to the device. This is done programmatically and requires that the world space has been initialized beforehand, to understand where that relative position exists in the setting. The Ground Plane samples provide a UI for mid-air placement that uses a cross-hairs metaphor. The design of your mid-air placement UI can be customized to suit a variety of use cases.