An augmented reality display system configured to align 3D content with a real object comprising skin of a wearer of the augmented reality display system or of a person other than the wearer, the system comprising: a frame configured to mount on the wearer; an augmented reality display (2005, 2006) attached to the frame and configured to direct images to an eye (2001, 2002) of the wearer; a light source configured to illuminate at least a portion of the skin by emitting invisible light; a light sensor configured to image said portion of said skin illuminated by said light source using said invisible light; and processing circuitry configured to detect a feature in the image formed using a reflected portion of the invisible light, the feature corresponding to a preexisting feature on or under said skin; store said feature to be used as a marker for virtual content; and determine information regarding the location of the object, the orientation of the object, or both based on one or more characteristics of the preexisting feature in the image formed using a reflected portion of the invisible light; wherein the processing circuity is configured to utilize the light source and the light sensor at a first frequency characterized in that said system comprises a depth sensor configured to detect a location of the skin, wherein the processing circuitry is configured to monitor the location of the skin using the depth sensor periodically at a second frequency higher than the first frequency. a frame configured to mount on the wearer; an augmented reality display (2005, 2006) attached to the frame and configured to direct images to an eye (2001, 2002) of the wearer; a light source configured to illuminate at least a portion of the skin by emitting invisible light; a light sensor configured to image said portion of said skin illuminated by said light source using said invisible light; and processing circuitry configured to detect a feature in the image formed using a reflected portion of the invisible light, the feature corresponding to a preexisting feature on or under said skin; store said feature to be used as a marker for virtual content; and determine information regarding the location of the object, the orientation of the object, or both based on one or more characteristics of the preexisting feature in the image formed using a reflected portion of the invisible light; wherein the processing circuity is configured to utilize the light source and the light sensor at a first frequency characterized in that said system comprises a depth sensor configured to detect a location of the skin, wherein the processing circuitry is configured to monitor the location of the skin using the depth sensor periodically at a second frequency higher than the first frequency. detect a feature in the image formed using a reflected portion of the invisible light, the feature corresponding to a preexisting feature on or under said skin; store said feature to be used as a marker for virtual content; and determine information regarding the location of the object, the orientation of the object, or both based on one or more characteristics of the preexisting feature in the image formed using a reflected portion of the invisible light; wherein the processing circuity is configured to utilize the light source and the light sensor at a first frequency characterized in that said system comprises a depth sensor configured to detect a location of the skin, wherein the processing circuitry is configured to monitor the location of the skin using the depth sensor periodically at a second frequency higher than the first frequency.