Enlighten probes

We recommend to use the automatic probe placement workflow and provide regions where probes are required.

If you want to use your own implementation of probe placement, provide regular grids or sets of probe positions.

Probe regions

To use the automatic probe placement workflow, when you export the enlighten scene, define the regions of space where probes are required.

In many cases you can determine this region automatically. For example, probes might be required to cover:

• the bounds of static meshes that are lit by probes, and
• the area of terrain where the character can walk.

In some cases you may need the artist to place hints in the world to indicate where probes are required, or to choose a resolution which provides the right balance between quality and cost.

Static meshes

To automatically place probes for a static mesh that is lit by probes, create an instance object and geometry object for the mesh. Add the type attribute Fully Dynamic and the probeResolution attribute. This defines a probe region to cover the surface of all meshes associated with the instance.

If the geometry object is configured as terrain, the probe region will extend directly above the mesh surface, along the axis specified by the verticalAxis attribute of the probesParameterSet. When you provide the waterPlane attribute of the probesParameterSet, Enlighten probes are not placed for terrain instances below this distance along verticalAxis.

Region objects

Add a probeRegion element to the scene with a unique name attribute.

To construct a region of space, create an object of type IPrecompInputProbeRegion. You must specify the voxelSize parameter to set the maximum resolution (e.g. minimum spacing between probes.) Probes are placed automatically on a sparse voxel grid with this resolution. All probe regions in the scene must use the same voxel size.

Call AddVolume, AddPoints, AddBoxes to define the shape and resolution of the region. The resolution parameter defines the voxel resolutions at which probes are placed to cover the specified shapes. Repeat as many times as you need to build up a single region with a complex shape and to vary resolution in different parts of the region. Where two regions with different resolutions overlap, the higher resolution takes priority. 

For example, assuming that your world units are centimeters, to construct a region for a city scene:

• specify voxelSize 200 for all probe regions in the scene,
• call AddBoxes with resolution FULL to define the shapes of building interiors,
• call AddVolume with a larger overlapping volume and resolution HALF to define the shape of exterior areas.

Save the region object in the scene root folder with the same name as the probeRegion element, and the .ipr extension.

Region groups

Set the zone attribute to group probe regions into as few groups as possible. For a small world, use a single zone for all regions in the scene. If your world is split into chunks for streaming, use the zone attribute to group probe regions into a single zone for each chunk.

Where two zones overlap in space, duplicate probes may be created. Try to avoid significant overlap at the boundary between two zones.

The precompute produces a single probe octree for each zone, and automatically splits this octree into a number of probe sets.

Grids and sets

There are two options for specifying the probe locations: the volume element, or the probeSet element.

To specify a regular grid of probes with a specific location, size and orientation, add a volume element. Add the size, position and basis elements to define the volume and the density of probes placed.

To create a probe set to place probes at specific locations, write code to create an object of type IPrecompInputProbeSet. Save the object in the same directory as the .scene file and add a probeSet element with the same name.

Radiosity parameters

To configure the probe data produced by the precompute, set the probesParamSet attribute to the name of a probesParameterSet element of the radiosity parameters.