These settings affect the calculation and display of particles created with the particle simulation system introduced in Cinema 4D 2024.4. Particle systems that use legacy Emitters or components of the XPresso-based Thinking Particles system are not affected by these settings.
This also has to do with the fact that only with the new particle system do you also have the option of having this simulated via the GPU, which is usually accompanied by extreme speed advantages. Therefore, when using the new particles, please also note the CPU and GPU settings in the Scene tab of the Simulation Scene presets.

Substeps[1..200]

The particles will be calculated internally with the animation frames. This can lead to some problems. Think, for example, of very fast-flying particles that need to be checked for collisions with thin objects. Viewed in the animation, a particle can still be in front of the object in frame 59 and already behind it in frame 60. The division into full animation frames therefore will not always work reliably enough.
For this reason, you will find the Continuous option on the particle Emitters, for example, which also generates particles internally in the period between animation frames. Otherwise, the effect you can see in the following video will occur. On the left you can see an Emitter with fast particles that are created with the Continuous option disabled. Gaps between the particles will become visible there. To the right, an Emitter with the Continuous option enabled can be seen for comparison.

This Substeps value can be used to control the calculation cycles of the particles even if they have already been generated and are subject to forces and Modifiers. This defines the additional calculation steps for particles within an animation frame. An increase in the value will lead to a mathematically and physically more precise behavior, with the acceptance of a correspondingly longer calculation time per animation frame.

Field Sampling Variance[0..1000%]

Particles can be influenced by fields, e.g., within Force objects, Conditions or Modifiers. To do this, samples of the values of the fields must be taken along the particle trajectory. Particularly in the case of fast-moving particles, it can be useful in such cases to be able to adapt or increase these samples specifically for fields. The effect can be seen as an example in the following video. There, particles are guided through a cube-shaped Random field, which is used within a Field condition to cause particles to bend sideways. Both emitters use the same settings and fields. The only difference is that a Field Sampling Variance of 0% is used on the left and 100% on the right. It can be clearly seen that more particles are sorted out on the right side of the field and turn off to the side. The scanning of the Random field is more precise there.

Precision

Here you can define the calculation accuracy of the simulation scene. As a rule, you will use 32 bits here. A lower bit depth can lead to mathematical rounding errors, which can cause the behavior of the particles to deviate from the expected result. However, a low bit depth can also have advantages, e.g.,, the storage of caches for large particle systems. This means that these files can be kept somewhat smaller compared to the same simulation with 32-bit precision.

Initial Capacity[256..2147483647]

A buffer size can be selected here, which will be used internally as memory for replaying the particle simulation. The defined value will be automatically increased internally to the next higher power of two.

Compactify Threshold[0..100%]

This setting influences the optimization of the particle data in order to enable smoother calculation and playback and at the same time optimize the memory requirements. For example, particles often have to be removed from the simulation once their lifetime has expired. The corresponding memory areas must be cleared and released again.
The percentage value represents the ratio between deleted and active particles at the end of each animation frame (particles that have just died/particles that are still active).
If this ratio is smaller than the threshold value, the memory area for the particle simulation will be optimized.

Download Particles

The particle simulation can be specially prepared for processing by the GPU and then often calculated correspondingly faster compared to the calculation on the CPU. You make this decision in the Scene tab of the Simulation Scene settings. However, this can also lead to disadvantages, as not all Generators that can then access the points in a Particle Group, for example, will also be executed on the GPU. In such cases, the particle data must also be copied back from the GPU to the normal working memory to which the CPU has access.
This step is carried out automatically in the Auto setting in order to keep the Particle Group object as up-to-date as possible, e.g.,, when a Generator accesses it. There may be situations where there are problems with this automatic update. In these cases, select On to force an update of the Particle Groups of the particle simulation for each animation frame. In the Off setting, the Particle Groups will not be updated.
This setting is only relevant for the calculation on the GPU. When using the CPU, the Particle Groups will automatically be updated in each animation frame.

Selection Highlighting

This function is very helpful for directly recognizing which particles are contained in which Particle Group even without changing the display of the particles when changing groups. You can see a simple example of this in the following image. There, particles were moved into different groups based on their percentage age across different conditions. Since all particles retain their color and size, it would be difficult to identify which particles are managed in which of the three groups.
However, as can also be seen in the illustration, all particle representations that are not contained in the currently selected Particle Group will now be desaturated. This makes it immediately clear that in this example, only the end of the particle stream will be contained in the third Particle Group.

Draw (Groupless Particles)

These settings only affect particles that have not been assigned to a group. This can happen, for example, if you simply delete a group already filled with particles in the Object Manager or simply remove a group link from one of the Emitter objects, for example.
Particles that do not belong to a group will not be automatically deleted, but can no longer be specifically addressed via Forces, Conditions or Modifiers, for example. It is also no longer possible to assign a Redshift Object tag or link these particles to Generators or Fields. Groupless particles can also not be rendered.
For this reason, an unique appearance and an unique color scheme can be defined here for these groupless particles so that they immediately catch the eye in the Viewports.

Draw Particles

Particles that do not belong to any of the Particle Groups in the scene will only be displayed if this option is active.

Draw Mode

Here you can select how the particles are to be displayed in the views. Various complex shapes are available, all of which can be individually adjusted in the display size using the separate Draw Size value:

• Points: The particles will be displayed as points or slices.
• Ticks: The particles awill be re displayed as four-point stars.

• Arrows: Arrow-shaped representations will be used, which start at their wide end at the position of the particles. The arrowheads will always point in the direction of flight of the particles and the length of the arrows represents the speed of a particle relative to its neighbors.
• Lines: This mode is similar to the Arrow display in terms of information content. Instead of arrows, however, simple lines will be used here that have a darker and a lighter section. The darker end of the line starts at the position of the particles and points with its lighter end in the direction of the particles' flight. Here, too, the respective line length represents the relative speed of the particles. Particles with short lines will be slower than particles with longer lines.
• Handles: Axis systems whose origin lies on the position of a particle will be drawn in here. The axis directions reflect the orientation of the respective particle axis system.

Draw Radius

Particles have a Radius property that can be used, for example, to define the size of the particle display during rendering. This property can also be displayed as a circle by activating this option. This circular representation always corresponds exactly to the Radius property of the particles and cannot be adjusted individually by using the Font Size setting.

Draw Size[0.10..16.00]

This value can be used to define the display size of the particles individually. Only the optional radius display will not be affected by this, as it always shows the exact Radius property of the particles as a circle.

Override Mode (Display)

By default, the displayed color of the particles is defined directly by the Emitter of the particles or by special Modifiers, such as the Color Mapper Modifier. However, you can also use this setting to overwrite this color evaluation, e.g.,, to make the group change of particles clearer by using a different color in the views. The following options are available:

• None: The actual color of the particles will also be used for their display in the views. As a rule, this is also the color with which the particles will be rendered. The color of the particles is defined directly by the Emitter when they are created and can then be changed using Modifiers.
• Constant: In this setting, the inherent color of the particles will be suppressed for the display and replaced by the Overwrite Color (Display).
• Direction: The flight directions of the particles will be broken down into X, Y and Z components, which will then become the red, green and blue values of their new display colors. Blue-colored particles mainly fly parallel to the Z-axis, green-colored particles travel in a vertical direction and red-colored particles fly parallel to the X-axis. Mixed colors indicate the corresponding mixing directions.

Override Color (Display)

You can configure your own color for the Constant Overwrite Mode (Display). Click on the color field to open a separate settings dialog with the typical color sliders. Otherwise, you can also click on the small arrow to the left of the color field to open the color sliders and define exact RGB or HSV color values, for example.