Translated from "fr 2003 sound Sonorisation des systèmes de clusters" — a Nevrax production guide describing how to set up audio for interior spaces using the cluster/portal visibility system. {.is-info}

This document describes the method used to add sound to interior spaces (cluster systems).

The work consists of first specifying three types of information: the materials of doors on portals, the environment effects (reverb models) in clusters, and the creation of named cluster groups for ambient sound placement.

In a second step, Georges sheets are created to associate cluster group names with sounds.

Steps 1 through 4 are performed by the 3D team. Step 5 is performed by the sound team using the sound group description document.

The first step is to create a cluster and portal system on the meshes to be given sound. In most cases, a cluster system already exists for visual clipping management (the original purpose of clusters and portals).

The sound system takes advantage of the geometric structures of clusters and portals to calculate sound propagation in interiors.

The constraints imposed by sound propagation are close to those imposed by visual clipping. But in certain cases, it will be necessary to add a few extra clusters and portals for correct propagation.

Example: In some buildings, elevators have not been clustered. To manage the occlusion of an elevator door when it closes, a cluster and a portal must be added.

Clusters and portals for the tavern.

For each portal, a material can be specified. This material affects sound propagation. By default, all portals are considered "transparent" to sound, meaning they are made of air.

For dynamic portals, a material can be specified for both the open and closed states.

Configuring a portal.

In the figure above, the settings for the portal corresponding to the tavern's exterior door are shown:

• A: The portal mesh is selected.
• B: The portal property is selected, and the portal is dynamic (it can open or close).
• C: Selection of occlusion models. When closed, the portal is associated with the THINDOOR (thin door) material. When open, the portal is "transparent" (no occlusion).

Environment effect models characterize the sound reverberation in a room or space (e.g. bathroom, padded corridor, auditorium, etc.).

These environment effects are applied to clusters. Additionally, the size of the cluster serves as a reference for setting the room size in the reverb model. Therefore, if the cluster is much larger than the actual volume of the mesh it surrounds, the environment effect could be disproportionate. That said, there is little chance anyone would notice :)

Environment effect on the corridor.

In the figure above, the effect settings for the tavern corridor are shown:

• A: The corridor cluster meshes are selected.
• B: The selected meshes are confirmed to be clusters.
• C: The HALLWAY (corridor) effect is assigned to these clusters.

To place ambient sounds in interiors, clusters must now be grouped and assigned a sound group name. Clusters should be grouped logically, keeping in mind the audio design possibilities.

Three important constraints must be followed when creating sound groups:

1. A naming convention (e.g. MA_SG_group_name for Matis SoundGroup).
2. Maintaining a text document containing the name of each group with a minimal description to locate and identify what the group represents.
3. Near-exhaustive creation of sound groups across all existing clusters.

These three constraints allow sound designers to place ambient sounds in interiors with maximum efficiency.

Configuring a sound group.

In the figure above, a sound group is assigned to a cluster:

• A: The cluster mesh(es) are selected.
• B: Confirmed to be clusters.
• C: The group FY_SG_taverne is assigned to the selected cluster(s).

The description file might look like this:

FYROS
----------------------------------
Tavern
FY_SG_taverne               The tavern interior
FY_SG_taverne_couloir        The corridor leading to the tavern

War School
FY_SG_rampe_access           The access ramp to the school
FY_SG_couloir_haut           The upper central corridor
FY_SG_assenceur              The elevator
FY_SG_couloir_bas            The lower central corridor
Etc...

The final step is to assign ambient sounds to certain sound groups.

This association is done by creating one or more Georges sheets based on the DFN sound_group.dfn. These sheets consist of a table of elements containing an association between a sound group name and a sound sheet name.

These sheets are placed by convention in the directory data/sound/cluster_sound.

Editing a SoundGroup association sheet.

In the image above, an association sheet is being edited in Georges:

• A: This is a sound_group type sheet.
• B: A freely resizable items table.
• C: The sound group FY_SG_taverne is specified.
• D: It is associated with the sound sheet taverne.sound.

Now, simply entering the tavern will trigger the taverne.sound ambient!