Voxel Size

Specifies the size of a voxel. Voxels are cubes. This value specifies their side length. When changing this value, the resolution will change accordingly.

Grid Size

specifies the size of the fluid container. The simulation will clip everything outside of this box. In most cases, the simulation will clip even more than that, trying to minimize the box that acutually needs to be simulated. See the Clip Below parameters of the fluid channel tabs for more details.

The info field Max Memory Usage shows the memory that the simulation would use if the simulation used all the space in this container.

Grid Offset

There are two ways of moving the fluid container in space during simulation. You can move the container object like any other object in the scene or you can this Grid Offset parameter. Moving the container as an object will move the container and the fluid in it. If you're moving the container using the Grid Offset parameter, only the container will move. The fluid will stay in place or be clipped at the new container boundaries.


Just like high-quality rendering, fluid simulation is a computationally very intensive task. Moreso than rendering however, detailed voxel grids require a lot of memory. A 128x128x128 grid (2 MegaVoxel) basically corresponds to 128 bitmap images with 128x128 32bit (=4byte) pixels for each channel we cache. The velocity channel is actually a vector channel, so it uses 3 times as much space. That's 2MegaVoxel x 4byte x 3 = 24MB for each frame - only for the velocity. Every additional channel uses another 8MB per frame.

Each frame is written to a separate .bcf file in the cache directory. Each .bcf file contains all active channels (see Simulation parameters) and the velocity, if you enable it (see Cache Velocity below). The filenames contain the frame number, so you can easily identify every single frame, for example to continue the simulation from that frame at a later time (see General parameters above).

While all frames are written to disk, TurbulenceFD will only keep a small number of frames in working memory and dynamically load frames from disk as necessary for rendering and in-editor previewing.

Cache Directory

Specifies the directory on disk where the simulation cache files are written to.

Relative to Content Directory

If checked, the directory above is specified as a path relative to the project's content directory.

Lock Cache

If checked the current cache directory is locked against accidental overwrite. In order to run a simulation on a locked cache, you have to uncheck this box first.

Compress Cache

If you are using very high resolution grids and disk space becomes an issue, you can enable compression. Note that compressing the cache also requires processing time which will slow down the simulation. However, especially when saving large caches to a network drive, it can balance out with the time it takes to transmit the data over the network, because compression can reduce the file size up to 60%.

Cache Temp./Dens./Fuel/Burn

Select whether to store either of these fluid channels to disk. You only need to store the channels you use as shader inputs. You can save memory by not caching channels that are not shaded.

However, if you want to continue a simulation from any previously simulated frame without re-simulating al prior frames, all active channels need to be cached.

Cache Velocity

Caching the velocity of the fluid allows you to use Velocity Displacement during rendering, continue or restart simulations from any frame of the cache and move particles through the fluid. However, it requires considerable amounts of disk space. Because velocity is a 3-dimensional vector, caching the velocity takes 3 times as much memory as for example the temperature field.

Cache Collision

Cache the collision field used by the simulation. You can use the viewport preview with this channel to check how voxelization of the collision objects has turned out. See the Collision Object parameter in the emitter's General tab for more information about collision object voxelization.

The collision field is a partial signed distance field. For values inside collision objects, each voxel value represents the negative distance to the closest point on the object's surface. Voxels that are not inside any collision object have a very large positive value.