Volumetrics

This extension actually consists of 3 types of volumetrics:

• "Constant density" - creates a cube shaped volumetric area in your scene which has a constant density. This is useful for very large atmospheric haze effects for example.

• "Noise3D" - this also functions as the constant density type except it also adds an adjustable 3D noise to create density variations in the volume.

• "Particle based" - this lets you use a particle simulation to define the volumetric density. You can either use particles directly in supported applications (such as Maya, 3ds Mac, Cinema4D, Softimage), or load an external particle file in several formats (.abc, .bin, .pxy, .prt, .rpc).

Constant density

This will actually be a separate cube shaped object in your scene, which can be manipulated like any other object (translated, rotated, scaled). The volumetrics will be visible only inside this cube shape. Please see your plugin documentation for specifics on how to add a Constant Density object to your scene. In Maxwell Studio, you can add it by right-clicking in the Object panel and choosing Create Extension Object>MaxwellVolumetric.

An example mimicking heavy atmospheric haze using the Constant Density cube encompassing the scene, and the resulting renders with/without the volumetrics. Note that a very low density of 0.003 was used since the Constant Density area was so large in this case (1km). The Maxwellsea extension was used to create the terrain.

Noise3D

As mentioned above, this type also uses a cubic shape to define the volume, but adds a 3D procedural noise to add some variation to the density. In the following examples, the density has been set very high to make it easier to see the changes to the noise parameters.

Seed

Define a starting seed for the randomization of the noise pattern

Detail

Create larger or smaller sized noise detail. In other applications this parameter is sometimes referred to as "wavelength".

Detail parameter from left to right: 2, 4, 8

Octaves

The number of times that the initial noise pattern should be repeated. With each repetition (octave) the noise will be half the size of the previous octave. The effect will look similar to having an initially smaller Detail, but the difference is that the larger initial Detail will still be visible, and the Octave parameter will add smaller noise to the initial larger noise pattern.

Octaves from left to right: 1,2,3. Detail level was kept at 3 and Persistance was kept at 0.6 for all renders.

Particle based

This type of volumetric will create density based on particles, either loading a particle file or by adding the Maxwell volumetric modifier to a particle simulation in your main application (please consult the documentation of your plugin on how to do this).

Radius multiplier

For any density to be visible in the render, the particles must first of all have a certain initial radius. This is determined by you when you create the particle simulation, depending on which scale you work in, and at what scale you have exported your scene to Maxwell. This parameter lets you multiply that radius - in case the particles have a too small radius, or you want to change the look of the volumetric. Increasing this parameter has the effect of making a more "puffy" less defined look.

If nothing appears in the render, this is the first parameter you should change. Generally, the idea is to avoid seeing individual particles and instead have a continuous looking smoke.

From left to right, changing the radius multiplier: Value of 2 (perhaps a bit too much), 1 (seems a good value in this case), 0.3 (too small)

Density multiplier

You can increase or decrease the amount of density that each particle will contribute with this parameter. Note that the final density will still be limited by the "Max final density" parameter.

Values of 2, 5, 100 ("Max final density" parameter was kept at 35 for all renders)

Min final density

The minium density in a particular cell of the volumetric object. In most cases you should leave this value at 0 as you don't want any

Max final density

The max allowable density in a particular cell of the volumetric object. Note that this parameter is also influenced by the Density Multiplier - a small density multiplier will not make the volumetric look more dense, even if the Max final density is very large. In fact, you should avoid setting this setting very high (for example more than a few hundred), especially if the density multiplier value is small. This will result in a similar look as if a smaller max final density value was used, with the downside that the render time will be substantially slower. As you can see in the example renders below, if the Density multiplier is already fairly large, then a Max final density value of around 100 will be enough even for the most "solid" volumetric simulations.

Values of 1, 10, 100 (Density multiplier was kept at 25 for all renders)

Cell size

The cell size should be considered as 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.