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Distributions are a group of data types that provide flexibility by allowing for constant values, random values within a range, values interpolated along a curve, and values driven by parameters. These are generally used in properties of Particle Systems and nodes within SoundCues.
Although regions are listed in alphabetical order within the editor, we will list them here in order of complexity. This is done simply to aid in understanding for those new to the concept.
Distribution Baking
No matter which type of distribution you use, you will always see the option Can be Baked just beneath it. This determines whether the numeric results of the distribution can be baked out into a lookup table. Baking values out to a lookup table is far more efficient than having to calculate random values or curve interpolations on the fly. For this reason, this option is on by default.
Should you run into edge cases in which the lookup table results lose critical information, you may uncheck this option so that the system checks the actual value on each tick. Naturally, this is a bit less efficient, but in rare cases where you have a critical look to achieve and the lookup tables are failing, the option is worth considering.
Distribution Types
Most particle properties utilize the DistributionFloat and DistributionVector types to allow for the maximum flexibility when creating particle systems. There are a variety of options available when using distribution types which will be detailed in the following sections.
Note that the actual usage of the value will vary, depending on the property that is using it. For example, the Initial Size of a particle is determined at the time that a particle spawns. If the distribution type is set to a constant curve for the property, then the emitter time at the spawning will be used to retrieve the desired value from the curve.
Float Distributions
Float distributions are utilized when there is a scalar property that is artistcontrolled. An example would be the lifetime of a particle, or the spawn rate of the emitter.
DistributionFloatConstant
This type is used to supply a value for the property that is constant. Below is a graphical representation of this value along a number line.
Constant float value which will not change.
When selected as the type, the following dialog will be provided for editing the value:
DistributionFloatConstant Properties 


Item 
Description 
Constant 
This is a static and unchanging number for a given property. 
DistributionFloatUniform
This distribution type is used to supply a range of values for the property. When evaluated, the value returned will be randomly set within the selected range.
Minimum value.
Maximum value.
Range from which a random value will be selected.
When selected as the type, the following dialog will be provided for editing the value:
DistributionFloatUniform Properties 


Item 
Description 
Min 
The minimum value for the random calculation. 
Max 
The maximum value for the random calculation. 
DistributionFloatConstantCurve
This type is used to supply a value for the property that is plotted on the graph editor over time. Whether the time is absolute (over the lifetime of the emitter) or relative (over the lifetime of the individual particle) is dependent on the module which utilizes the distribution.
Keyframe point.
Interpolation curve. Final value will be pulled based on this curve's value at a given time.
Tangent handles  These define how the curve flows into and out of a keyframe.
When selected as the type, the following dialog will be provided for editing the value:
Note that all of the fields can be handedited, but utilizing the curve editor window is the suggested approach for editing these values.
DistributionFloatConstantCurve Properties 


Item 
Description 

Points 
This is an array property that contains all the points in your curve. You may create points here using the button. However, it will generally be easier and more intuitive to add points in the graph editor. 

Point Properties 

InVal 
This is the location of the point along the graph's horizontal axis, generally calculated as time. 

OutVal 
This is the location of the point along the graph's vertical axis, generally calculated as property value. 

ArriveTangent 
Provides the angle of the incoming tangent for the point. Useful values range from about 150 to 150. 

LeaveTangent 
Provides the angle of the outgoing tangent for the point. Useful values range from about 150 to 150. 

InterpMode 
Allows the user to choose between a variety of interpolation modes for the curve. See the [Curve Editor User Guide](Basics/ToolsAndEditors/CurveEditor) page for more details.

DistributionFloatUniformCurve
This type is used to supply a range of values for the property that is plotted on the graph editor over time. At each point in time, a random value is selected that exists within the min and max curves.
Min curve  This defines the minimum value as it changes over time.
Max curve  This defines the maximum value as it changes over time.
Resultant range  This is the area of the graph from which the final value is selected at each point in time.
When selected as the type, the following dialog will be provided for editing the value:
As with the ConstantCurve type, it is recommended that this distribution type be edited via the curve editor.
DistributionFloatUniformCurve Properties 


Item 
Description 

Points 
This is an array property that contains all the points in your curve. You may create points here using the button. However, it will generally be easier and more intuitive to add points in the graph editor. 

Point Properties 

InVal 
This is the location of the point along the graph's horizontal axis, generally calculated as time. 

OutVal 
This is the location of the point along the graph's vertical axis, generally calculated as property value. In the case of a Uniform Curve, this property will contain an X and Y value representing the Min and Max of the output, respectively. 

ArriveTangent 
Provides the angle of the incoming tangent for the points for both X and Y (min and max). Useful values range from about 150 to 150. 

LeaveTangent 
Provides the angle of the outgoing tangent for the points for both X and Y (min and max). Useful values range from about 150 to 150. 

InterpMode 
Allows the user to choose between a variety of interpolation modes for the curve. See the [Curve Editor User Guide](Basics/ToolsAndEditors/CurveEditor) page for more details.

DistributionFloatParticleParam
This type is used to allow for simple gamecode setting of parameters for emitters, so that they can be manipulated via code, Blueprints, or Matinee. It provides the ability to map input values from one range to another, allowing for tweaking of the parameter in "Cascadespace" without requiring gameplay code to be updated. Once an established Input range is determined by the gameplay coder, the artist is free to adjust the property through the Output mapping.
When selected as the type, the following dialog will be provided for editing the value:
Input to Output is linearly remapped, so: MinInput of 0 with a MaxInput of 5, MinOutput of 0 with a MaxOutput of 100 means that if you pass 2 in as your input, your output will be 40.
This is very useful for setting simple 01 inputs that map to multiple outputs, since you can share particle parameter variables by name. For example, you could set up the SpawnRate to be driven by Particle Parameter Foo, and set the inputs from 01, and the outputs from 20200, and also use Foo in the InitialSize with the same inputs but an output of 1020.
In code, the programmer would write something like:
ParticleComponent>SetFloatParameter('MyParameter', CurrentParameter);
DistributionFloatParticleParameter Properties 


Item 
Description 
Parameter Name 
This is the name by which the parameter will be referenced in code or in Blueprint scripting. 
Min Input 
This is the minimum value that can be passed into the distribution, typically via game code. 
Max Input 
This is the maximum value that can be passed into the distribution, typically via game code. 
Min Output 
This is the minimum value that can be output into Cascade, as mapped from the range of inputs. 
Max Output 
This is the maximum value that can be output into Cascade, as mapped from the range of inputs. 
Param Mode 
This controls how the input values will be used. See the Param Mode Flag table below. 
Constant 
This provides a default value for the system in the absence of any inputs. 
ParamMode Flag 
Description 

DPM_Normal 
Leave the input value alone. 
DPM_Abs 
Use the absolute value of the input value before remapping. 
DPM_Direct 
Use the input value directly (no remapping). 
Vector Distributions
Vector distributions are utilized when there is a vectorbased property that is artistcontrolled. An example would be the size or velocity of a particle.
DistributionVectorConstant
This type is used to supply a value for the property that is constant.
XAxis value
YAxis value
ZAxis value
When selected as the type, the following dialog will be provided for editing the value:
The LockedAxes flag allows for the user to lock the values of one axis to that of another. The following flags are supported:
DistributionVectorConstant Properties 


Item 
Description 
Constant 
This is a static and unchanging number for a given property. In a vector value, this contains values for X, Y, and Z. 
Locked Axes 
This locks one of the 3 axes to another axis, simplifying the distribution. See the Locked Axes Flag table below. 
Locked Axes Flag 
Description 

EDVLF_None 
No axis is locked to another. 
EDVLF_XY 
The Yaxis is locked to the Xaxis value. 
EDVLF_XZ 
The Zaxis is locked to the Xaxis value. 
EDVLF_YZ 
The Zaxis is locked to the Yaxis value. 
EDVLF_XYZ 
The YandZaxes are locked to the Xaxis value. 
NOTE: When the lock flags are active, the values are NOT reflected in the property window setting. Ie, the Y value will not display the X contents when the LockedAxes flag is set to EDVLF_XY. Only when the value is retrieved from the distribution (in code) will the locked axes value be applied.
DistributionVectorUniform
This type is used to supply a range of values for the property. When evaluated, the value returned will be randomly set within the selected range.
XAxis Min value
XAxis Max value
XAxis random range
YAxis Min value
YAxis Max value
YAxis random range
ZAxis Min value
ZAxis Max value
ZAxis random range
When selected as the type, the following dialog will be provided for editing the value:
DistributionVectorUniform Properties 


Item 
Description 
Min 
The minimum value for the random calculation. In the case of a Vector Uniform, this will contain values for X, Y, and Z. 
Max 
The maximum value for the random calculation. In the case of a Vector Uniform, this will contain values for X, Y, and Z. 
Use Extremes 
Indicates that the values for Min and Max should be used as well, rather than just the values between them. 
Locked Axes Flag 
Description 

EDVLF_None 
No axis is locked to another. 
EDVLF_XY 
The Yaxis is locked to the Xaxis value. 
EDVLF_XZ 
The Zaxis is locked to the Xaxis value. 
EDVLF_YZ 
The Zaxis is locked to the Yaxis value. 
EDVLF_XYZ 
The YandZaxes are locked to the Xaxis value. 
The Mirror Flags allow for mirroring the Min/Max values for each component of the value. The following flags are supported for mirroring:
MirrorFlags 
Description 

EDVMF_Same 
Use the Max value for Min as well. 
EDVMF_Different 
Use each value as set. 
EDVMF_Mirror 
The Min value will be the inverse of the Max (Max * 1). 
The 0, 1, and 2 immediately under the Mirror Flags property represent the X, Y, and Z axes, respectively.
DistributionVectorConstantCurve
This type is used to supply a value for the property that is plotted on the graph editor over time. Whether the time is absolute (over the lifetime of the emitter) or relative (over the lifetime of the individual particle) is dependent on the module which utilizes the distribution.
XAxis Curve Point 0
XAxis Curve Point 1
XAxis interpolation curve
YAxis Curve Point 0
YAxis Curve Point 1
YAxis interpolation curve
ZAxis Curve Point 0
ZAxis Curve Point 1
ZAxis interpolation curve
When selected as the type, the following dialog will be provided for editing the value:
As with the FloatConstantCurve type, it is recommended that this distribution type be edited via the curve editor.
NOTE: When the LockedAxes flag is set to something other than EDVLF_None for a ConstantCurve distribution, the CurveEditor will not display the locked axis to avoid confusion. For example, if the flag is set to EDVLF_XY, the curve editor will contain only the X and Z curves.
DistributionFloatConstantCurve Properties 


Item 
Description 

Points 
This is an array property that contains all the points in your curve. You may create points here using the button. However, it will generally be easier and more intuitive to add points in the graph editor. 

Point Properties 

InVal 
This is the location of the point along the graph's horizontal axis, generally calculated as time. 

OutVal 
This is the location of the point along the graph's vertical axis, generally calculated as property value. 

ArriveTangent 
Provides the angle of the incoming tangent for the point. Useful values range from about 150 to 150. 

LeaveTangent 
Provides the angle of the outgoing tangent for the point. Useful values range from about 150 to 150. 

InterpMode 
Allows the user to choose between a variety of interpolation modes for the curve. See the [Curve Editor User Guide](Basics/ToolsAndEditors/CurveEditor) page for more details.

Locked Axes Flag 
Description 

EDVLF_None 
No axis is locked to another. 
EDVLF_XY 
The Yaxis is locked to the Xaxis value. 
EDVLF_XZ 
The Zaxis is locked to the Xaxis value. 
EDVLF_YZ 
The Zaxis is locked to the Yaxis value. 
EDVLF_XYZ 
The YandZaxes are locked to the Xaxis value. 
DistributionVectorUniformCurve
This type is used to supply a range of values for the property that is plotted on the graph editor over time. The final value will be chosen at random from between the Min and Max curves for each axis.
XAxis Min curve
XAxis Max curve
XAxis random interpolated range
YAxis Min curve
YAxis Max curve
YAxis random interpolated range
ZAxis Min curve
ZAxis Max curve
ZAxis random interpolated range
When selected as the type, the following dialog will be provided for editing the value:
DistributionVectorUniformCurve Properties 


Item 
Description 

Points 
This is an array property that contains all the points in your curve. You may create points here using the button. However, it will generally be easier and more intuitive to add points in the graph editor. 

Point Properties 

InVal 
This is the location of the point along the graph's horizontal axis, generally calculated as time. 

OutVal 
This is the location of the point along the graph's vertical axis, generally calculated as property value. In the case of a Vector Uniform Curve, this property will contain an V1 and V2 value representing the Min and Max of the output, respectively. Each of those values will contain values for the X, Y, and Z axes. 

ArriveTangent 
Provides the angle of the incoming tangent for the points for both V1 and V2 (min and max), which each contain values for X, Y, and Z. Useful values range from about 150 to 150. In the case of a Vector Uniform Curve, this property will contain an V1 and V2 value representing the Min and Max of the output, respectively. Each of those values will contain values for the X, Y, and Z axes. 

LeaveTangent 
Provides the angle of the outgoing tangent for the points for both X and Y (min and max). Useful values range from about 150 to 150. In the case of a Vector Uniform Curve, this property will contain an V1 and V2 value representing the Min and Max of the output, respectively. Each of those values will contain values for the X, Y, and Z axes. 

InterpMode 
Allows the user to choose between a variety of interpolation modes for the curve. See the [Curve Editor User Guide](Basics/ToolsAndEditors/CurveEditor) page for more details.


Use Extremes 
Indicates that the values for Min and Max should be used as well, rather than just the values between them. 
Locked Axes Flag 
Description 

EDVLF_None 
No axis is locked to another. 
EDVLF_XY 
The Yaxis is locked to the Xaxis value. 
EDVLF_XZ 
The Zaxis is locked to the Xaxis value. 
EDVLF_YZ 
The Zaxis is locked to the Yaxis value. 
EDVLF_XYZ 
The YandZaxes are locked to the Xaxis value. 
The Mirror Flags allow for mirroring the Min/Max values for each component of the value. The following flags are supported for mirroring:
MirrorFlags 
Description 

EDVMF_Same 
Use the Max value for Min as well. 
EDVMF_Different 
Use each value as set. 
EDVMF_Mirror 
The Min value will be the inverse of the Max (Max * 1). 
As with other curve types, it is recommended that this distribution type be edited via the curve editor.
DistributionVectorParticleParam
This type is the vector equivalent of the FloatParticleParam type discussed above. It allows a value to be manipulated via code, Blueprints, or Matinee.
When selected as the type, the following dialog will be provided for editing the value:
DistributionFloatParticleParameter Properties 


Item 
Description 
Parameter Name 
This is the name by which the parameter will be referenced in code or in Blueprint scripting. 
Min Input 
This is the minimum value that can be passed into the distribution, typically via game code. 
Max Input 
This is the maximum value that can be passed into the distribution, typically via game code. 
Min Output 
This is the minimum value that can be output into Cascade, as mapped from the range of inputs. 
Max Output 
This is the maximum value that can be output into Cascade, as mapped from the range of inputs. 
Param Mode 
This controls how the input values will be used. See the Param Mode Flag table below. 
Constant 
This provides a default value for the system in the absence of any inputs. 
Locked Axes Flag 
Description 

EDVLF_None 
No axis is locked to another. 
EDVLF_XY 
The Yaxis is locked to the Xaxis value. 
EDVLF_XZ 
The Zaxis is locked to the Xaxis value. 
EDVLF_YZ 
The Zaxis is locked to the Yaxis value. 
EDVLF_XYZ 
The YandZaxes are locked to the Xaxis value. 
ParamMode Flag 
Description 

DPM_Normal 
Leave the input value alone. 
DPM_Abs 
Use the absolute value of the input value before remapping. 
DPM_Direct 
Use the input value directly (no remapping). 