The density modifier sets the spatial distribution of density.

As all modifiers, the properties panel of the density modifier contains a textfield where you can identify this particular modifier with an identifying Name label. It is also displayed in the modifier stack.

Below the name, there is a switch to enable/disable the modifier without deleting it.

The density d is proportional to the f0 parameter and the magnitude, i.e. d = f0 * magnitude.

The magnitude is defined as a function of 3D position in the modifier graph that opens when you click on the Edit button (see below).

Within each modifier, the distribution is separable in its coordinates. That means that the magnitude is given as the product of the distribution in each coordinate. For instance, in cartesian coordinates you have

d(x,y,z) = f0 * mag_x (x) * mag_y (y) * mag_z (z)

More than one density modifier can be used in the modifier stack. You can combine them using the Operation drop-down selector, which includes operators of Replace, Add and Scale. This allows very complex distributions to be constructed, especially since different coordinate systems can be combined.

The Replace operator overwrites any density modifiers above it in the modifier stack and is combined only with density modifiers below.

The Add, of course, adds the density to any previous density modifiers.

The Scale operator multiplies the previous densities by this modifier. Note that this does not only mean the application of the current f0 multiplier, but the complete density modifier including the spatial dependence given by the modifier graph.

The texture editor has the usual control button to add, del, move, copy and paste. Then there is a stack with the textures that are multiplied together before they are applied. On the left, there is a preview window, which shows approximately the scale of the noise pattern as it will be in the rendered view. The slider at the bottom allows you to move through the direction perpendicular to the image plane.

Note that the pattern is applied in coordinates of world space. Meaning that it will not grow with an object that grows in time (as animated in the Animation Module). The surface of an expanding nebula will run through this pattern. An expanding pattern requires surface mapping, which is currently not implemented.

At the bottom of the texture editor you can set the scale of the noise pattern, as well as an offset in space. By default the scale in x, y and z directions are set equal. To make elongated filaments disable the Lock button and make the scales different to the required extend.

The Exponent controls the density contrast between the high and low values of the density pattern. For sparse filaments you need values of order 10.

The complexity of the pattern is controlled by the Frequency parameter.

To invert the dark and bright regions change the setting of the Invert button.