Viewport Display Modes

When loading an OpenVDB file in an Arnold Volume object, you should see the volume in the viewport with different display settings. The display settings adapt the display of the volume objects based on the viewport mode.

Standard

Wireframe Override

Note that the look will not change drastically in the viewport between the Standard and High-Quality display modes. 

Wireframe

Box display of the quads to show the wireframe shape of the volume.

Flat

No shading applied on the volume object.

Standard

Basic shading of the volume object.

High Quality

Ambient occlusion, shadows, and lights are applied to the volume object.

Object Display Properties

Uses the same display option modes as other mesh objects in 3ds Max.

Display as Box

Only the bounding box shows the extent of the volume object.

Vertex Ticks

This is based on the quality settings (samples) of the volume object. It displays the voxels as ticks (using the color of the standard tick in 3ds Max for vertices). As opposed to the mesh objects, this hides the volume display when showing in voxel mode. Only shows the voxels. With meshes, the polygons are still displayed. But in the context of the volume, it would be redundant visual information. 

Display options

If no display options are chosen in the object properties this just displays based on the current display mode. 

Viewport Display (volume object)

Volume object that contains grids, such as the Arnold volume object (Fog) or level sets (SDF (signed distance fields)), display properties as a rollout on top of the object's user interface in the modifier stack. 

The viewport display rollout only contains functionality for the viewport display options. No functions that affect the rendering in Arnold are part of this rollout.

Quality

This is what is displayed in the viewport to represent the selected channel/grid of the volume in volume display mode.

Show

Selects the viewport volume display type. The choice of quality will affect the performance.

Volume (default)

Render Preview
  • This is based on the object's current material (info on current material type applied to the object).

This option won't be presented when the volume contains only Signed Density Field grids. In that case, the volume will be represented as an object in the viewport (mesh or voxels). The Volume option will show the object like any other object. This option is presented only if the shader applied to the volume object is supported in the viewport. E.g.: the option will be enabled if the Arnold standard_volume shader is assigned to a volume in the viewport.

Active Voxels

 Wireframe

Bounding Box

Grids / Channels

A list of all the grids in the OpenVDB file is visible in the list view. Only one grid can be selected at once in the list. The selected grid in the list is the one displayed in the viewport. When there are multiple grids loaded, each grid has its own settings.

VDB volume with four channels/grids: density, fuel, heat, and temperature.

Grid List items: 

Float grid

Float grid.

Level set grid

Signed density field grid (level set).

Vector and point grids are not currently supported.

Display Settings for Selected Grid/Channel

The name of the selected Grid/Channel.

Display As

Defines visual representation of the volume in the viewport. Defines what options are available for the type of grid. There are three types of grids:

Display as:

Color (volume color).
Blackbody:
Gradient Map

Display as: Gradient Map

The Gradient Map can be instanced in the material editor for editing like any other map in 3ds Max.

Turbo Spectrum

Display as: Turbo Spectrum

Vector Grid

Display as:

Color Per Axis

X color (red default). X-axis color. Y color (green default) Y-axis color. Z color (blue default) Z-axis color. It represents the overall direction of the vector without indication of the length.

Field options:

  • Magnitude spinner (length of the lines).
    • Defines the maximum length of the lines.
      • Lines are of proportional length based on the vector length.
  • Resolution (number of lines).
    • Defines how many lines are displayed to represent the vector field.
  • Color Start widget (default red). Start of the line color.
    • Start point color for the line representing the vector.
  • Color End widget (default green). End of the line color.
    • Endpoint color for the line representing the vector.
      • Behavior:
        • Display settings are shown when in Show: Volume mode.
          • If no grid is selected (Render Preview, no grid present in VDB) or if using display options (wireframe, active voxels, bounding box):
            • No display settings are shown.
        • If a grid of known type and property is selected it defaults to the correct display method until the options are edited.
          • Density: color.
          • Temperature: blackbody.
          • Velocity: fields.
          • Settings are all remembered with the grid and display methods (sticky options).
            • When users switch grids or display types and come back to a given grid or display type, the settings are restored.

Curve Editors

  • When the curve editor button is clicked, the Graph dialog pops up near the cursor.

    • Opacity
      • X-axis: channel values distribution and name
      • Y-axis: Opacity gradient 
    • Offset
      • X-axis: channel values distribution and name
      • Y-axis: Gradients rendering
      • Blackbody: 0k to 30,000k

Slice

  • Axis:
    • Enables slicing on a given axis or leaves the slice tool off.
    • When an axis is selected, show the slice options:
      • Position: position of the slice center in the volume bounding box. Default at 0.0 on the axis which is normalized centered in the volume
        • -1.0 is at the minimum position and +1.0 is at the maximum position.
      • Thickness: same units at a position to define how wide is the slice. More voxels are shown when the thickness is bigger. Min value: 0..0, Max value: 2.0.