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The cell size should be considered the "resolution" of the volumetric object. The smaller the cell size, the finer the resolution. Just as a bitmap image can reveal more detail when zoomed in if it contains a lot of pixels. The cell size parameter is necessary in order to keep the RAM usage under control. So the final RAM consumption is not influenced by the number of particles in your simulation, but instead on the number of cells which are created at render time, which define the resolution of the volumetric object.
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Decrease this setting carefully as very small changes can cause your RAM consumption to increase a lot. |
How cell density is determined
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This series of images is ment to show that with a small enough cell size, each particle can be very well defined (in these renders the cell size was reduced to 2mm (a setting of 0.002), and secondly, how the Density Multiplier parameter can act as a sort of falloff between areas of density and no density. The Max Final Density was 500 for all renders. You can see that as the Density Multiplier decreases, there is a larger falloff between no density to the areas of maximum density. When the Density Multiplier is very high, there is a very sharp falloff, making the volumetric shape have much sharper contours.
Extra particles
This parameter adds extra particles around the simulated particles. The simulated particles must have some velocity as the extra particles will be scattered based on the trajectory of the simulated particles. So if your particles aren't moving, this parameter will not change anything.
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