This extension actually consists of
...
4 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).
- Volume file based - this works currently with the OpenVDB file format which is a format that describes a volume based on voxels and is not particle based. Usually these types of files can be created with RealFlow, Houdini, Maya. The advantage of using this format is that you can store very detailed and large smoke/explosion simulations without the need to store billions of individual particles.
| Info |
|---|
Any Maxwell material (except emitters) can be applied to the volumetric object (or particles), but generally a normal lambert material works just fine. |
...
How to use the Maxwell Volumetrics extension
The details will depend on what plugin you are using, or whether you are using Maxwell Studio, but in general, you add this extension as an object to your scene and it will be represented by a cube (in the case of Constant density and Noise3D), points that show the particle cloud in the case of Particle based, and a cube bounding box representation in the case of the Volume based type. Please see your specific plugin documentation for details on how to add an volumetric object to your scene. You then apply any Maxwell material to this object.
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.
...
Values of 1, 10, 100 (Density multiplier was kept at 25 for all renders)
Cell size
The cell size should be considered the "resolution" of the volumetric object. The parameter uses a real world unit of 1m. 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.
| Warning |
|---|
Decrease this setting carefully as very small changes can cause your RAM consumption to increase a lot. |
...
The above illustration shows a particle that happens to have the same size as the cell. But even in this case, it isn't certain that this cell will show any density if the Density Multiplier and Final Density settings are too small, because the cell still has a certain distance to search before finding this particle. The longer this search distance is, the more faded the density becomes.
Lets Let's see some more examples:
A 10cm large cube of particles, where each particle is 2cm in diameter, and each cell is 1cm in size (setting of 0.01). The cells are small, so a smaller search distance inside the cell is needed to find a particle, thus we see some density created in each cell in this case. Notice that we are not seeing the round shape of the particles, but rather the square shape of each of the cells. The cells (the "resolution") would need to be even smaller to start mimicking the round shape of the particles.
...
Here the cell size was increased to 2cm. Since the distance each cell has to search has increased, nothing appears in the render. We could raise the Radius Multiplier in this case to make the particles bigger, or lower the cell size again to make some density reappear. We could in fact also also raise the the cell size even more, and some density would appear again. See the next illustration for why this happens.
...
Now the cell size is 3cm and we start seeing some density again. This can seem very unintuitive at first, but looking at the grid of cells, it is clear that now now some corners corners of some cells are actually actually closer to to a particle compared to when the grid was set to 2cm. So we start seeing a very rough, square representation of these particles, because the cell size is so large.
...
Extra particles set to 0, 10, 200. Dispersion was set to 0.1 (10cm) in this case. RAM usage only very slightly increased even with 200 extra particles per particle. The right most image shows the particle radius increased to avoid seeing the individual particles.
Extra particles dispersion
The distance (in meters) that the extra particles should be allowed to be randomly distributed around a sphere based on the original position of their "parent" particle.
Extra particles deformation
The new particles can be generated randomly inside a sphere based on the position of the "parent" particle, or inside an ellipsoid with this value of eccentricity. The ellipsoid is aligned along the direction of the parent particles speed.
Motion blur factor
You can control the amount of motion blur visible on the particles, separately from the scenes main motion blur settings. If you want the particles to look blurrier as they move, increase this parameter.