Preview

Detail Reduction – Decreases the grid detail in the preview. A value of 0 means no reduction. Increase this value if the interface starts to lag due to the cache files being very large. This parameter controls both the viewport preview and the GPU preview.

Auto Reduction – Enables automatic adjustment of the Detail Reduction parameter to improve display performance. The preview detail is reduced up to a point where the preview displays fast without blocking the interface. Note that the detail only decreases automatically but does not increase.

Voxel Preview Mode – Determines how the volume grid file is previewed in the viewport.

Triangles – Previewing particles as Triangles is more cumbersome and slow. This is the default viewport preview mode.
Points – Previewing particles as Points with "drawn-on" circles is faster and recommended. Previewing Points also allows for smoother camera movement in the viewport, as this mode does not rely on regenerating the object cache when moving the camera. The points are always facing the camera and there is no need for manual billboarding. 

Point Size – A multiplier for the size of the points when the Voxel Preview Mode is set to Points. 

Only if Selected – When enabled, the contents of the cache file are only shown when the V-Ray Volume Grid is selected.

Show Box – When enabled, displays the Volume Grid's loaded cache bounding box in the viewport.

Graph Cells – When enabled and Show Box is enabled, displays a lattice with the cell sizes on the sides of the Volume Grid's box.

Show mesh – When enabled, shows the Isosurface as a mesh. The Isosurface is defined in the Surface section of the Rendering rollout. This mode overrides the Voxel Preview mode. Note that if Mode is set to Ocean Mesh in the Rendering settings, the surface is generated in the viewport with low mesh resolution so as not to slow down the user interface significantly.

Only the Overlap Of – When enabled, all channels in a cell must meet the selected threshold conditions to visualize the cell.

Temperature/Liquid – Enables the representation of the temperature and liquid.

Temperature Low/High Range – Specifies the lowest and highest values of the temperature.

Smoke – Enables the representation of the smoke.

Smoke Low/High Range – Specifies the lowest and highest values of the smoke.

Fuel – Enables the representation of the fuel.

Fuel Low/High Range – Specifies the lowest and highest values of the fuel.

Velocity – Enables the representation of the velocity.

Velocity Low/High Range – Specifies the lowest and highest values of the velocity.

Velocity Streamlines – Traces the velocity field of the cache files to generate a streamlined preview.

As Rainbow – Represents the Velocity Streamlines in rainbow colors.

Velocity Streamlines Low/High Range - Specifies the lowest and highest values of the velocity streamlines.

Streamlines Length – Signifies the maximum length of each streamline in the preview. Adjusting the value will provide you with a guide/preview of the velocity field's motion. The Line's length is measured in voxels; at the lowest setting, the Streamlines will be no larger than a voxel.

RGB – Enables the representation of the RGB channel.

RGB Low/ High Range – Specifies the lowest and highest values of RGB.

Auto Range – When enabled, automatically adjusts the preview ranges of visible channels for the current frame so that important data is always visible and the preview is always quick.

Draw Just a Slice – When enabled, only a voxel-thick cross-section of the grid is visible. This works for voxels and velocity streamlines but not for the Mesh Preview. It allows for a better view of occluded details and can help when previewing very rich data, such as velocity fields, or in order to see underwater cavities.

Along Axis – Specifies the axis along which the grid is sliced.
Disabled – Disables the option.

Slice Level – Specifies the offset of the slice from the bottom center of the grid in voxels.