Some volume file formats, such as OpenVDB, allow storing much larger datasets while being optimized for random access to volume data, which is more efficient for rendering.
OpenVDB, developed at DreamWorks Animation, is an open source C++ library comprising a novel hierarchical data structure and a suite of tools for the efficient storage and manipulation of sparse volumetric data discretized on three-dimensional grids.
Rendering of volumes should not be confused with Atmosphere Volume, which is a global effect.
A polymesh node now can be a volume container when
step_size is greater than zero, and in that mode it will interpret the assigned shader as a volume shader. This can be done by adding a Mesh Volume tag to the polymesh.
Custom AOVs are not currently supported with volumes.
Volumes can only receive indirect lighting from other emissive volumes when the Volume Ray Depth is above 0.
The built-in volume types are OpenVDB, Box or Sphere. You can install custom third-party volume plugins (e.g. copy the volume binary to the $C4D_INSTALL/C4DtoA/procedurals folder) as well which appear in the list.
The Render tab contains generic shape parameters, such as the visibility controls, shadow cast, matte, etc. See the Geometry parameters page for more details.
Enlarge the volume by Padding. This is useful when displacing a volume with a noise for example. Note that this slack applies not only to the bounding box but also to the voxels used for ray extents inside the bounding box. When velocity motion blur is enabled, some extra padding is computed, based on the maximum value of the velocity field, and the maximum of the velocity padding and user padding is applied. When padding exceeds the bounding box maximum dimension, the ray extents acceleration makes little sense and is disabled, so you should set the padding as tightly as possible.
For best performance, this should be set as low as possible, while still covering the maximum displacement amount.
The amount of padding to add to the volume bounds for displacement
The location of the VDB file. File sequences are automatically recognized and numbers are replaced with # characters in the file name. You can manually edit the path if you don't want padding in the file name.
Make sure that the IPR is not running when setting the file path, otherwise the bounding box will not display at the correct size in the viewport.
Defines the first frame of the animation when a frame sequence is defined (with # is used in the path).
Defines the last frame of the animation when a frame sequence is defined (with # is used in the path).
Defines the increment of the animation when a frame sequence is defined (with # is used in the path). For example start frame 0, end frame 10, step frame 3 selects frame 0, 3, 6, 9 from the animation.
Defines which frame of the scene the animation starts at. For example offset 2 means that the first frame of the animation is at frame 2. Offset -2 positions the third frame of the animation at frame 0 of the scene.
Defines how the animation is repeated.
- none: no repeat, nothing is displayed when the animation is ended.
- freeze: keeps the last frame rendered when moving further on the timeline.
- repeat: repeats the animation from the beginning.
- ping pong: will animate forward, then in reverse, then forward again, and so on.
Scales the volume according to the Export scale defined in the render settings. For instance if the Export scale is 1 m and the volume is specified as 1 cm, then it is scaled down by 0.01.
The density and emission of the Standard Volume shader depends on the scale, which is not updated by the plugin automatically. When you scale down a volume, you have to scale the density and emission intensity up.
Displays the grids (channels) available in the selected OpenVDB file.
A list of OpenVDB grids to read and make available as channels in the volume shading context. Examples of Grid names are density, fuel, heat, temperature or velocity.
Either 1 vector grid (eg.
vel) or 3 float grids (eg.
vel.z) representing the velocity field, to be used for motion blur. No motion blur will occur if an invalid combination of grids or if no grids are specified. Note that all velocity grids declared here are also available as channels in the shading context.
A scale factor for the velocity field. A value of 0 disables motion blur.
Controls filtering of noisy velocities resulting in the faster rendering of motion blur from physics simulations. The default value of 0.001 should have little to no visual impact. Setting it to zero disables filtering entirely.
A scaling factor applied to the step size, mostly useful when the Volume Step is set to Automatic, to modulate the automatic value. For low frequency, smoke-like volumes, a value of 4 is a reasonable starting point.
More information about volume Step Size can be found here.
Currently, Atmosphere Volume does not compose well against volumes. This is because atmosphere's return a single flat result that is opacity mapped on top of whatever is in the background of the pixel.
Left: floor plane geometry hidden. Right: floor plane geometry visible. Fluid renders incorrectly. Click images above to view animation.