Graphics Reference
In-Depth Information
Resolution
In terms of the time and memory needed for calculating the fluid simulation, and also in terms of the quality of
the results, the most significant parameter to set is the Resolution parameter. As I mentioned before, the fluid
simulation domain is divided into discrete units called
voxels
.The density ofvoxels in the domain is the resolu-
tion of the fluid simulation. Resolution in this sense is directly analogous to image resolution; higher resolution
yieldsclearerandmore-detailed representations. Thenumericalresolutionvalueyouenterindicatesthenumber
of voxels that make up the longest edge of your domain. The amount of memory required to calculate a domain
of a certain resolution does not depend in any way on the absolute size of the object or on the real-world size of
the simulation, but it does depend on the volume of the domain with respect to the longest edge of the domain.
This means that for any given resolution, a perfect cube-shaped domain will require the most memory.
In practice, the resolution you need is dependent on two factors: the precision or fineness of the interaction
between the fluid and other objects and the size of the area in which the fluid has to interact. Having a fluid
that interacts in a convincing way with small objects but also involves a large area (and remember, splashing
counts!) requires high resolutions. If your resolution is too low, your fluid will appear thick and gluey even if
its viscosity is set correctly. In the bottle example shown in
Figure 7-21
,
higher resolution (over 300) is needed
because the fluid has to be fine enough to come out of the bottle smoothly, but the domain needs to be big
enough to allow for a fairly spread-out splash. This example required slightly more than 3 gigabytes of RAM.
Theamountofmemoryneededgoesupwiththecubedvalueoftheresolution,meaningthatslightlyhigherres-
olutioncantakeconsiderablymorememory.Blender'sfluidsimulatorhasamaximumresolutionof512,which
requires almost 13 gigabytes to process. Hardware is not the only bottleneck here. Some operating systems also
place limits on the amount of RAM that can be used at one time by a particular program.
