Abstract: An artificial reality system includes a head mounted display (HMD) and a hand-held device. A virtual boundary can provide for user safety during an artificial reality session. For example, the virtual boundary may be defined to protect the user from collisions with physical objects, such as walls, furniture, or the like, while the user is immersed in the artificial reality session. The artificial reality system can constrain the predicted motion path of a portion of a user's body based on body configuration parameters and range of motion of the joints associated with the body portion. The artificial reality system can then use the constrained motion paths to determine whether or not the virtual boundary warning should be activated.

Abstract: The disclosed artificial reality system can provide a user self representation in an artificial reality environment based on a self portion from an image of the user. The artificial reality system can generate the self representation by applying a machine learning model to classify the self portion of the image. The machine learning model can be trained to identify self portions in images based on a set of training images, with portions tagged as either depicting a user from a self-perspective or not. The artificial reality system can display the self portion as a self representation in the artificial reality environment by positioning them in the artificial reality environment relative to the user's perspective in the artificial reality environment. The artificial reality system can also identify movements of the user and can adjust the self representation to match the user's movement, providing more accurate self representations.

Abstract: A virtual space configuration system of an artificial reality system can detect a user posture and provide various corresponding customizations of the system's virtual space. The virtual space configuration system can, when a user is in a seated posture, provide for seated virtual space customizations. In various implementations, these customizations can include allowing adjustment of a floor height; setting a flag that can be surfaced to applications to adjust the applications' mechanics for seated users; customizing display of virtual space boundaries when in seated mode to be less intrusive; providing options to detect when a user leaves seated mode and trigger corresponding actions; provide a passthrough workspace area allowing a user to interact with certain real-world objects naturally without having to remove a virtual reality headset; or automatically determining virtual space dimensions for seated users.

Abstract: A system includes processing circuitry configured to receive sensor data regarding a user operating a head mounted display (HMD). The processing circuitry is configured to identify a plurality of reference points of a pose of the user based at least on the sensor data. The processing circuitry is configured to apply one or more models to the plurality of reference points to determine a type of the pose of the user. The processing circuitry is configured to select a mode of operation of the HMD responsive to the type of the pose.

Abstract: Techniques and systems for non-contrast enhanced magnetic resonance angiography and venography (MRAV) are described. For example, within one cardiac cycle of a subject, a single shot acquisition of non-suppressed arterial MR signals and a single shot acquisition of non-suppressed venous MR signals are employed. Radio frequency (RF) saturation pulses may be applied to one or more slabs such that MR signals indicative of venous blood that flows into the arterial imaging slice are substantially suppressed and MR signals indicative of arterial blood that flows in the venous imaging slice are substantially suppressed. The RF saturation pulses and the single shot acquisitions may be timed such that one or more of the single shot acquisitions occur during substantially steady state inflow of blood into the respective imaging slice. In this manner, k-space data may be acquired from arterial specific and venous specific imaging slices occurring within a single cardiac cycle.

Abstract: Techniques and systems for non-contrast enhanced magnetic resonance angiography and venography (MRAV) are described. For example, within one cardiac cycle of a subject, a single shot acquisition of non-suppressed arterial MR signals and a single shot acquisition of non-suppressed venous MR signals are employed. Radio frequency (RF) saturation pulses may be applied to one or more slabs such that MR signals indicative of venous blood that flows into the arterial imaging slice are substantially suppressed and MR signals indicative of arterial blood that flows in the venous imaging slice are substantially suppressed. The RF saturation pulses and the single shot acquisitions may be timed such that one or more of the single shot acquisitions occur during substantially steady state inflow of blood into the respective imaging slice. In this manner, k-space data may be acquired from arterial specific and venous specific imaging slices occurring within a single cardiac cycle.