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Volumes#

The Volume geometry is an object for which visibility is defined by its density. For more information about volume render settings please refer here.

Small Tree

Density Cutoff#

The Density Cutoff attribute allows to cut into the density of your volume to fine tune the shape of your volumes without the need to rely systematically on the potentially expensive Progressive Rendering mode of the 3D View. That way you get ultra fast, yet accurate, feedback when set-dressing volumes.

Density Cutoff set to 0

Density Cutoff set to 0025

Density Cutoff set to 01

Density Cutoff set to 05

Note

This settings only affect the display of the 3D View

Volume Box#

Volume box can be used to create optimized atmospheres supporting efficient light scattering in a participating media. Lights in volumes are automatically scattered according to their shape and falloff. The volume box can enclose any kind of Scene Objects including volumes.

Volume Box surrounding the scene

Box Volume surrounding the scene

Same scene without the Volume Box

Same scene without the Box Volume

Note

While multiple scattering is supported (global illumination within the volume), render times can get pretty slow to have a noise free image. It's recommended to exclude global illumination lights in volume boxes.

Density Falloff#

By default, the box volume approximate a thin uniform atmosphere. However, it is possible to apply a falloff to vary its density according to the distance and curves.

Density falloff driven with 3 curves (controlling density on X, Y, Z)

Density falloff driven with 3 curves controlling density on X, Y, Z

It is also possible to texture its density.

A volume box having its density textured (cell noise)

A volume box having its density textured cell noise

Note

Complex texture graphs used as density texture input can really slow down evaluation.

Step Count/Step Size#

When the density is controlled by a texture or curves, you must specify the step used to sample the volume density. There are two ways of specifying the step. Either using Step Count or Step Size. You can select either methods using the Step Mode attribute.

Tip

If your volume is enclosed, favor Step Count. If it is surrounding you scene, then favor instead Step Size.

Volume File#

Volume files import their density from an OpenVDB file. You can also access to properties (attributes) that are declared in volume file using the Extract Property texture.

Attribute Description
Filename Path to the volume file.
Grid Mode When the file contains grids ending in .x, .y or .z it is possible to leave them as it is or merge them into a single grid
Density Property Set the name of the property containing the density. This property is used for the raytracing.
Velocity Property Set the name of the property containing the velocity. This property is used for the raytracing.
Density Offset Value directly added to the density at evaluation.
Density Multiplier Set the density of the volume.
Density Cutoff Removes intersections with a density below this value in the 3d View.
Velocity Multiplier Set the scale of the velocities.
Velocity Space Specify in which space the velocities are expressed.

Example of an imported OpenVDB file.

Example of an imported OpenVdb file

Delayed Loading#

Open VDB supports delayed loading of volume grids so that Clarisse only loads needed parts in memory during rendering. Please note that delayed loading is enabled by default.

To enable or disable delayed loading, go to Edit > Preferences... In the Open VDB section check/uncheck Use Delayed Loading. In the preferences panel, you will see two additional options: File Size Mode and File Max Size.

File Size Mode#

By default, File Size Mode is set to Unlimited so that all Open VDB files are delayed loaded. By setting, File Size Mode to Limited, you can tell Clarisse to only activate delayed loading on files that are larger than the specified File Max Size.

Warning

Open VDB delayed loading can introduce slow downs on the Windows platform. If you experience any unusual slow downs, please disable Use Delayed Load in the Open VDB section of Edit > Preferences...

Volume Surface#

The Volume Surface allows you to generate a volume from an input geometry. To create a volume from a geometry, just connect the geometry you want on the Surface attribute. Volume Surface works best with enclosed geometries.

Geometry on the left, Volume Surface on the right

Geometry on the left, Volume Surface on the right

Step Count/Step Size#

When the density is controlled by a texture or curves, you must specify the step used to sample the volume density. There are two ways of specifying the step. Either using Step Count or Step Size. You can select either methods using the Step Mode attribute.

Tip

If your volume is enclosed, favor Step Count. If it is surrounding you scene, then favor instead Step Size.