Emission
Here you can assign the spline geometry where new particles should be created. To do this, drag a spline object from the Object Manager into this field or first click on the pipette to the right of the linking field and then click on a spline object in the Object Manager.
Incidentally, if a spline geometry is already selected when the Spline Emitter is created, it is automatically linked here.
There are two modes available that allow you to define where the particles should be created on the spline:
- Points: The particles are only created where points are present on the spline. This includes both the real points and the intermediate points, the number and arrangement of which you can configure directly in the interpolation settings of the spline. The area to be evaluated on the spline can be restricted using a vertex map and the vertical distance from the spline in which the points should be created can also be set.
- Along: The particles are created locally independent of the points along the spline curve. Particles can be generated at fixed intervals or randomly along the curve. A vertical distance from the spline within which the particles are created can also be defined here.
The images above show examples of how to use the Points mode. Below you can see examples of the Along mode.
In Points Source mode, you can assign a Vertex Map of the spline object here, which can be used to restrict the area where particles are created. Since there can only be two states for the use of points, either a point is used to generate particles or not, a threshold value can also be used that defines the minimum weighting of the vertex map from which a point starts to emit.
Restriction Threshold[0..100%]
If you use a Vertex Map with Source Points as Restriction of the area in which particles should be created, enter the minimum weighting of the Vertex Map at which a spline point should create particles here.
This setting is only available in Along Mode and offers two additional options:
- Interval: You have additional setting options to define a distance between the points at which particles are created along the spline. The image above shows an example of this at the bottom-left.
- Random: Particles are created randomly along the entire spline curve.
With Source Along in combination with Interval Pattern, you can define the distance between the points at which the particles are created along the spline.
This is the vertical distance from the spline at which the particles should be created. With a Thickness of 0, the particles are created exactly on the spline. You can also use Thickness Variance to add randomness to this distance.
This is the maximum deviation from the set Thickness, which is interpreted as a random variation in the distance between the particles and the spline.
This option is used to enable or disable the Emitter. Only when enabled will the subsequent settings be evaluated, with which, for example, the time of the first emission or the number of particles created are defined. Animating this option can be used, for example, to end particle emission if continuous particle creation has been activated.
Here you can define the first animation frame from which particles should be created.
- Shot: All particles are created in one go at the time of the defined Start Frame. The Emitter will then switch off automatically. This mode is therefore ideal for generating the required Count of particles in one go. Please note that the number of particles generated in Points Source mode depends primarily on the number of points on the spline and cannot be set separately.
- Constant: This creates a continuous stream of particles that generates the specified Rate of particles per animation frame or per second of the animation. By activating the Range option, a time period can be defined for this mode after which the emission stops automatically.
- Pulse: The particles are produced at regular intervals separated by time. The number of animation frames in which particles are created and the number of frames in which the emission is stopped can be set. Such behavior is similar to the regular breaking of waves on a beach, for example.
In Shot Emission Mode, you set the number of particles to be generated in one go here. Please note that the setting is not available when using the Points Source. There, the number of particles is defined by the number of points at which the particles are created. In the Per Frame Emission Mode, for example, one new particle is created per spline point per animation frame. When using Per Second, a particle quantity corresponding to the spline point number is created per second of the animation.
This setting is only available for Along Source mode. In Points Source mode, the number of particles created is defined by the number of spline points instead.
This is the number of particles in Constant Emission Mode. How this value is converted is defined using the following buttons:
- Per Frame: The number of particles defined in the Rate is created in each individual animation frame as long as the Emitter is active. In Points Source mode, a number of particles per frame corresponding to the number of spline points is automatically created.
- Per Second:The number of particles set in Rate is evenly distributed during each second of the animation. In Points Source mode, a number of particles per second corresponding to the number of spline points is automatically generated.
This setting is only available for Source Along. In Points Source mode, the number of particles created is defined by the number of spline points instead.
This number of particles is produced within the time period defined under Duration. A Distribution curve is available which can be used to control how this number of particles should be distributed over the defined time period.
If the Continuous Emission Mode has been selected, a Duration can be defined by activating the Range option, after which the emission is automatically stopped.
In Pulse Emission Mode, the period of active emission is also set here, but the emission is not completed afterwards, but is repeated again after the defined Gap.
In Pulse Emission Mode, enter the gap between the cycles in which particles are created here.
In Pulse Emission Mode, this curve can be used to control when the particles should be generated within the active Emitter cycle. The left edge of the curve controls the number of particles at the start of a cycle and the right edge controls the number of particles at the end of the active cycle.
Exemplary variation of the particles emitted in a pulse via the Distribution curve.
This option is active by default and ensures that particles are also created in the time between the animation frames. This prevents gaps or steps in the particle flow.
The particles are formed randomly on the Emitter surface or in the Emitter volume. This value forms the basis for this random calculation. There are also many Properties settings that offer a random variation. These also use this Seed value.
Here you can create the link to a Particle Group in which the particles generated by the Emitter will be managed. By default, a new group is created together with the Emitter, which is automatically linked here. If this group is deleted, you can also call up a new Particle Group yourself in the Simulate menu and assign it by dragging it into this field or use an existing group. This step is shortened by clicking the Create Group button. A new group is automatically created, which is linked for this Emitter. Clicking on the pipette symbol to the right of the Group field activates a selection tool that lets you click directly on a Particle Group in the Object Manager to create a link.
If an Emitter is used without an assigned group, its particles are automatically assigned display properties from the Scene Settings. You will find a section for the display of groupless particles under Simulation/Particles. By default, these are colored purple and marked with small plus signs.
Density Distribution
In this section you will find options to influence the placement of the newly created particles on the emitter spline.
From left to right, here are examples of Uniform, Noise, Fields and Vertex Map density control for green emitted particles on a flower spline
- Uniform: This is the mode that was also used by default in C4D versions prior to 2025.2. New particles are placed evenly along the entire spline Geometry.
- Noise: The noise settings known from other places are offered to describe the pattern and size of a spatial structure. Particles then only occur on the assigned spline where values above 0 occur in this noise structure. The full particle density - as calculated in Uniform mode - can then only be observed where the noise structure reaches its maximum values. At the intermediate noise levels, i.e. values between 0 and 1, correspondingly fewer new particles are created in these areas. As particles intended for generation are deleted directly at the spline emitter in this mode if the noise values there are too low, the total number of remaining particles will be reduced accordingly. You can compensate for this using the separate Attempts value, which determines a corresponding number of evenly distributed positions for each particle to be generated in order to find a permissible starting position. This means that - with correspondingly higher Attempts values - the number of particles to be generated can still be achieved despite filtering out by the noise structure.
- Fields: The values of Field Objects can be used to control the emission density. Similar to the use of a noise structure, the new particles are initially positioned evenly on the spline emitter. In the second step, the falloff values of the assigned field objects are evaluated. If the particle density is below the field value at the corresponding position, the new particles are automatically deleted there. This always results in a reduction of the originally intended number of particles at the emitter. In the example in the figure above, a spherical field was used to only allow particles within a defined radius.
- Vertex Map: A Vertex Map Tag can be assigned here, which has been assigned to the emitting geometry. Vertex Map Tags can be configured by individually painting them with values between 0 and 1 (see explanations on the Paint Tool) or, for example, via field objects assigned in the tag. On the far right of the figure above you will find an example of a Vertex Map generated by individual painting. Particles are only produced in the outer areas of the Flower spline.
Noise
These settings are only visible if you activate Noise for Distribution.
The calculation of the Noise pattern is based on this value. A change in the Seed value therefore also leads to a recalculation of the selected noise structure.
Here you can choose the right one from the various patterns. These are three-dimensional structures that can be configured in the axis system of the emitter or the world and with individual scaling along all axis directions. It is also possible to evolve these patterns automatically:
Here you can select whether the noise structure should move with the local system of the emitter or whether it should be a stationary noise whose origin lies in the global world axis system.
This defines the amount of detail in the Noise structure. Larger values create correspondingly more variations in the pattern. Small values lead to a loss of contrast and details, as well as to a softening of the structure. This setting is not available for the noise types Box, Cell, Mod Noise, Perlin and VL Noise.
You can use these values to scale the Noise structure individually along the three spatial directions. Proportional scaling is also possible via the Scale value.
This allows the Noise to be scaled proportionally. Individual scaling for each of the three axis directions is also possible via Relative Scale.
The Noise structures can also be changed over time. Use this value to specify the speed of these changes. By default, 0 is used here, which results in a static structure.
Almost all noise types (exception: Electric and Gas) offer this parameter, which causes the noise to loop after the defined time in seconds(Animation Speed must be greater than 0). The Noise state is then repeated after the entered seconds. A value of 0 turns this effect off.
When activated, a determined noise value is used simultaneously for the red, green and blue color components. This results in pure gray or brightness values. If the option is switched off, individual noise brightnesses are calculated for each of the three color components. The brightness of this color is then used for the final evaluation of the noise value.
These two parameters are used to move the Noise through the 3D space. Movement is a direction vector that you use to define the direction in which the Noise should move. Use the Speed value to regulate the movement speed of the noise structure.
Please note that the speed is also dependent on Noise Space, as the coordinate systems defined there can differ greatly from one another.
This can be used to limit the brightness values that the Noise should provide. By default, Low Clip is 0% and High Clip is 100%. This means that all brightnesses can be output uncropped between 0% and 100% by the Noise. Increasing the Low Clip means that all brightnesses that are lower than defined for Low Clip are already output as black. Similarly, reducing High Clip results in gray values above the brightness of High Clip being output as white
In fact, this mechanism can be used not only to sharpen a Noise structure and to strengthen the contrast, but also to invert the brightness values. To do this, simply reverse the original arrangement of the clipping values. With Low Clip 100% and High Clip 0%, you get an inverted Noise.
This is used to adjust the general brightness value of the Noise. Values above 0% increase the brightness, values below 0% reduce it.
This allows us to reduce or increase the contrast of the Noise brightnesses. Contrast describes the range of brightness values. With a low contrast, the differences between the Noise brightnesses supplied are therefore smaller. Greater Contrast leads to greater differences in brightness between the noise brightnesses calculated. This often results in the brightness transitions being more abrupt and less smooth compared to using a lower Contrast. In terms of emission, a greater contrast results in sharper boundaries between the areas on the emitter where particles are produced and those that remain completely empty.
This area only appears when Distribution Fields is activated and enables the use of Field Objects to assign an individual density within the particle distribution. Fields offer a wide range of shapes and also allow shaders and audio files to be evaluated, for example. In addition, several fields can be combined to use even more complex density control criteria.
Similar to the use of noise structures, fields usually also generate values between 0.0 and 1.0. The larger the sampled field value, the more particles of the original, uniform density distribution are retained. Conversely, in areas with low field values, correspondingly fewer particles are produced at the emitter. This means that the originally configured number of new particles to be generated is lower after the fields have been evaluated.
The operation of this area and the available objects and options correspond to the identical operating elements that you can also find on the Deformers, for example. Follow these links to find out everything you need to know about Fields and how to use them:
If required, you can read all about the various Field objects here.
How to use the Fields area is documented here.
The accuracy of Field sampling can be adjusted via the Field Sampling Variance in the Particle Simulation Settings.
This field only appears when Vertex Map is activated for the Distribution of the new particles and enables the assignment of a Vertex Map Tag, which must be present in the Object Manager on the spline Geometry used for the emission. Simply drag this tag from there into this field. Only those sections of the geometry with Vertex Map values above 0 are then taken into account for the emission. As with the use of the Noise Distribution, this results in a reduction of the actually configured number of particles in the areas with Vertex Map values below 1. In order to bring the particle density back to the original value, new positions can be calculated for the particles to be deleted. Enter the number of attempts required to find a new, valid position for the particles under Attempts.
This value is only available when using Noise and Vertex Map to control the Distribution of new particles at the emitter. Originally, new particles are always generated uniformly along the emitter shape or in the emitter volume. Where the values in the selected noise are too small, the new particles are then deleted. This therefore reduces the number of newly generated particles compared to the default, which was configured via the Count, Rate or Pulse value on the emitter. This effect can be compensated for by increasing this Attempts value.
Whenever a newly created particle should actually be deleted again directly by evaluating the Noise structure or the Vertex Map, additional attempts are made to find a new, valid position for this particle. The lower the values within the Noise or Vertex Map, i.e. the larger the areas on the emitter where fewer or no particles should be created, the larger the number of Attempts should be selected in order to achieve the originally configured number of particles again.
On the left one Attempt, on the right 10 Attempts were made to give particles a permissible position in a noise structure along the emitter spline. The higher number of Attempts increases the probability that the originally selected number of new particles to be generated will be achieved. Note the areas marked in red to compare the two results. If more Attempts are used, more particles will appear, especially in the sparsely occupied areas on the left.