Basic
The Sample Channel loads a scalar VDB grid to drive the Volume Scalar Attribute. A VDB grid is loaded by typing its name into the channel field, for example, typing "density" directly into the field to load a density channel.
This field is case sensitive.
In the examples below different channels are loaded, the results are similar but they are not the same, note the difference in volume density for each. For example, when the temperature channel is used the edges are much softer because each channel has different values.
|
|
|
| Sample Channel: "density" | "temperature" | "color" |
Depending on which software or simulation system was used to create the VDB data, there may be variations in the names under which the properties of the volume simulation are saved. In this presets menu, you will therefore find some common simulation systems and the strings they use for the volume properties for direct access.
Controls the base value used in all voxels within the volume bounding box, including ones that appear empty. This can be used to set a constant value throughout the VDB. In most situations, this should be left at the default value of 0 so empty voxels stay empty.
|
|
|
|
| Default Value: 0 | 0.005 | 0.05 | 0.5 |
Controls how the voxels are displaced in scene units. The Position Offset is a vector input, the X, Y, and Z fields control how far a voxel is pushed in each direction. Displacing a volume can make it appear less dense.
If you want the same displacement on multiple volume components, like density and emission, use the same Position Offset on all components. On the other hand, different Position Offsets can be used for increased variety and control.
When using a texture for Position Offset, keep in mind the output values depending on what type of shading node is used. For example, when using a noise, by default it outputs a greyscale color from 0 to 1. Not only is this generally a small value, resulting in weak displacement, but since it starts at 0 it also means the volume will only be displaced in one direction along an axis. In order for displacement to appear centered on the volume's original position the 0 to 1 range should be remapped from -1 to +1 in all axes using a vector change range to allow displacement in all directions.
|
|
|
|
| Position Offset X: 100 Position Offset Y: 0 Position Offset Z: 0 |
0 100 0 |
0 0 100 |
100 100 100 |
Controls the input range of the VDB channel.
This does not affect displacement intensity.
| Old Min: 0 Old Max: 1 - 10 |
Controls the output range of the VDB channel. This controls the output into a Standard Volume shader, be certain to use appropriate values for the attribute that is being driven. For example, if using a Volume Scalar to drive temperature, the New Max should be set to something like 6500 to represent the maximum temperature of the volume.
This does not affect displacement intensity.
| New Min: 0 New Max: 1 - 10 |