Methods, apparatus and systems for modelling audio objects with extent

An apparatus for modelling extended audio objects for audio rendering in a virtual or augmented reality environment, the apparatus comprising:

• a processor configured to:
• obtain an extent representation indicative of a geometric form of an extended audio object and information relating to one or more first audio sources that are associated with the extended audio object,
• obtain a relative point closest to a user position in the virtual or augmented reality environment, using the extent representation indicative of the geometric form of the extended audio object, wherein obtaining the relative point using the extent representation indicative of the geometric form of the extended audio object comprises obtaining the relative point on the geometric form,
• determine an extent parameter for the extent representation based on the user position and the relative point, the extent parameter describing a spatial extension of the extended audio object perceived at the user position,
• determine positions of one or more second audio sources, relative to the user position, for modelling the extended audio object,
• output a modified representation of the extended audio object for modelling the extended audio object, the modified representation including the extent parameter and the positions of the one or more second audio sources, and
• render the extended audio object based on the modified representation of the extended audio object, wherein the extended audio object is rendered using the determined positions of the one or more second audio sources and the extent parameter.