Inputs

On the left-hand side of the modifier group, you can query the various properties of the particles to which the modifier has access. As a rule, these are the particles of the particle group under which the modifier has been subordinated. If you have selected the All mode for Included Particles (Read Only), the properties of all particles in the simulation scene can also be queried under All Particle Data.

Position

The positions of all particles to which the modifier has access are displayed here.

Unique ID

This is a unique number for each particle that remains constant throughout the life of the particle. None of these integer values can therefore occur twice. However, as all particles are always taken into account here, much larger values can also arise when outputting the Unique IDsof a particle group if other particles exist outside this group. If you require consecutive numbering that only contains the particles managed by the modifier, you can therefore also usethe input for Current index, although this value can then change for each particle, e.g., if new particles are added to the group influenced by the modifier. In the explanations of Current Index you will also find a small example that illustrates the difference between these two parameters.

Radius

Here you can read out the radii of the processed particles.

Velocity

This vector describes the speed and direction of flight of each particle that the modifier can access. The length of the vector corresponds to the flight speed and the direction of the vector corresponds to the direction of flight. A speed with the vector (0, 0, 100) means, for example, that the particle flies exactly in the Z direction, because the normalization of the vector results in 0, 0, 1, i.e., the Z axis. In this case, the flight speed is 100 cm / second, which corresponds to the length of the vector (0, 0, 100).

Color

Here you can see the RGB color value of the particles and its alpha component. The red, green and blue color components are between 0 and 1. An alpha value of 1 corresponds to a fully visible color, whereas a particle with an alpha value of 0 is completely transparent (with a corresponding evaluation of the alpha value in a material).

Age

The current age of the particles, measured in seconds. If you want to use the age in images instead, simply multiply this value by your frame rate (see Scene Presets).

Lifetime

The defined service life of each particle, output in seconds, as defined directly at the emitter, for example. When the Age of the particle reaches its Lifetime, the particle is automatically removed from the simulation. If you want to use the lifespan in pictures instead, simply multiply this value by your frame rate (see Scene presets).

Distance

This is the distance traveled by each particle.

Alignment

A matrix is output here which describes the axis directions of each particle.

Angular Velocity

This gives you a vector that describes the axis of rotation and also the rotational speed of each particle. The length of the vector indicates the speed of rotation and the direction of the vector indicates the position of the axis of rotation around which the rotation takes place. Note that the rotational speed is output in radians. A vector 0, 0 , 3.1415 therefore means that the axis of rotation corresponds exactly to the direction of the Z-axis (the normalization of the vector results in 0,0,1) and the speed of rotation corresponds to 180° per second (180°*(3.1415/pi)).

Group Index

This integer value indicates the group in which the particles are contained. The counting method starts at 1 for the top group in the Object Manager. The next subsequent group in the Object Manager is indicated by index 2 and so on. Rearranging the groups in the Object Manager therefore also changes their indices.

Field value

If fields have also been assigned in the Fields area of the modifier, their influence can be queried here. Normally, these values range from 0 (the particle is not influenced by the fields) to 1 (the particle is completely influenced by the fields). This value can be used, for example, to control a Mix node in order to adjust the strength of the modifier effect depending on the field strength.

Field direction

Vectors can also be generated via fields, e.g., if you use a Volume Generator in Vector mode within the modifier's Field list. The directions of these vectors are shown here for each particle that can be accessed by the modifier. In the following example, these vectors lead to a change in direction of the particles.

Field color

Fields can also be used to assign color values if they are listed in the modifier's Field list. The corresponding color value for each particle can then be read out here. You will find an example below.

Current index

Each particle is managed internally with an integer number, comparable to the indices of points on a polygon object. This value allows each particle to be clearly identified and tracked. Only the indices of the particles managed by the modifier are output at this port. The first particle is assigned the number 0, the second the number 1 and so on. However, this assignment is not static, but can change, e.g., if new particles are added to the particle group influenced by the modifier. The Unique ID value is also available. This includes all particles in the simulation in the indexing of the particles, including those that are not influenced by the modifier and are managed in other groups. This Unique ID remains constant for each particle during its lifetime and can therefore also be used to calculate static values for the particles, in contrast to Current Index. The following illustration shows the difference between these values using a simple example.

In this example, the index is read out and divided by a high number in order to subsequently change the color of the particles as a red component. Two emitters are used, each emitting into its own group. Only the lower particle flow in the figure is changed in color by the modifier. The Current Index of the particles is evaluated on the left and the global Unique ID for the coloring is evaluated on the right. Since the Unique ID also takes into account the green particles in the upper group when counting, higher values for the red portion of the colors are achieved much faster (as shown in the figure on the right).

Particle count

Here you can see the number of particles that are affected by this modifier.

Time step

This value, measured in fractions of a second, indicates the amount of time that has passed since the last simulation image. Please note that this step size can change with the selected Frame Rate of your simulation. For example, if you are working with 25 frames per second, the time step per animation frame will be 0.04 (1/25). For an animation with 30 frames per second, however, the time step per frame is 0.0333 (1/30).
You can use this value, for example, to calculate time-dependent changes to the particle properties, as this output is independent of the Substeps of the simulation and the choice of Execution Mode on the modifier. For example, if you want to change the radii of the particles by exactly 2 cm per second, use a multiplier for the values 2 and Time Step and add the result to the current radius of the particles.

Modifier matrix

This is the matrix of the Particle Node Modifier. This gives you access to the position and axis directions of the modifier, for example, and allows you to include these in the manipulation of the particle properties. For example, the position of the modifier could be used as a target point to change the velocity vectors of the particles, as in the following example.
First, a normalized vector is calculated between the position of the modifier and the current position of the particles. Then the current velocity of the particles is also normalized to obtain two direction vectors, each of which is one unit long. A Mix Node, whose mixing strength is controlled by a multiple of the Time Step value, calculates a new vector that represents a new direction between the current flight direction and the direct flight direction towards the position of the modifier. This gives us a time delay in the change of the velocity vectors.

Since the flight speeds themselves should not change, the length of the current speed is calculated and multiplied by the normalized result of the Mix Node before this result is written to the speed of the particles.

The following video shows the effect of this circuit, with the position of the modifier indicated by a red ball.

All particle data

Here you receive an array containing particle data for iterating, i.e., for reading and searching yourself. This is actually only required if you want to access the field effect of other particles, for example. Otherwise, the properties of other particles can also be read out via a Get Particle Property Array Node.
You specify which particle data this is with the mode for Included Particles (Read Only), which you can find in the Object settings of the modifier. If Masked is selected, only the particle data to which the modifier has access is available within the Particle Node Modifier, i.e., usually the particles of the group under which the modifier has been subordinated. In All mode, all particles of the simulation and their properties are therefore available within the Node modifier. This would therefore be the right setting if, for example, you want to calculate interactions between the particles of different groups or read properties of particles that are otherwise not influenced by this modifier.
By connecting a Iterate Collection Node, you not only have access to the total number of particles but also to all properties that are also available via the standard inputs on the Particle Node Modifier.