Geometrical Interactions,
Occlusion and Reflections

This chapter deals with one of the major unresolved challenges of interactive audio: the representation of reflecting and occluding objects in the simulated world, so that echoes and acoustic shadows are realistically rendered in a complex and potentially changing 3D environment. It contrasts static and mobile geometry, existing graphics and physics geometry and how they are authored, and the handling of collisions, contact sounds and moving obstacles.

The chapter presents and compares tested techniques for dynamically adjusting reverb in game and VR environments, noting their relative costs in design and programming effort and offline and realtime processing.

Concepts explored include efficient asynchronous bulk ray tracing, the authoring and use of custom audio geometry, challenges getting the team to mark up and maintain audio properties consistently, the quantification and interpretation of surface reflectivity and the authoring and visualisation of effect area meshes which control reverberation, sound area meshes controlling where sounds are triggered and how they are heard and further uses for such meshes. It notes optimisations for mainly-2D worlds, combining automatic and manual entry and editing techniques and the appropriate use of 'cheap shapes' such as spheres and boxes.

Working holiday: The author constructs a rather irregular man-sized octahedron to illustrate some geometric points at Cornwall's Eden Project.

Geometrical Interactions,Occlusion and Reflections

Further reading

Geometrical Interactions,
Occlusion and Reflections