Random POP

Summary

The Random POP takes its input and either (1) generates a new attribute containing random values, or (2) sets, adds or multiplies an existing attribute by a random value for each point.

The random values can be applied to point, vertex or primitive attributes.

By default, the random values are uniformly distributed between 0 and 1, but there is a variety of alternate distributions controlled with the Type menu. These include Gaussian (also known as Normal) distribution (where most points are near the center of the range), two values randomly chosen with a fraction probability of each (Two Values), a random Direction vector (within a certain cone angle) which always has length of 1, random float3 vectors within a unit Sphere, and Exponential which is an exponential dropoff above 0 separately in each axis.

The random values can be generated within a specified range (Value A and Value B), and then optionally clamped between two values.

There is an option to generate 2 or more points for every input point to increase the density of points around the source points. (Extra Points per Source Point)

The random values can also be restricted to certain point, vertex or primitive Groups.

Tip: You can get random distributions radially around a point by using the Projection POP by generating random numbers in polar space and converting to Cartesian.

Per-point mapping of parameters - The Random POP has a Map page, which allows every point to get a different value for Amplitude, Offset, Exponent, Period, Value A and B and other parameters. In this mechanism, a separate attribute in the input contains values that override (or add to / multiply by) the parameter value. See Mapping POP Attributes to Parameters.

Parameters - Random Page

Extra Points per Source Point extrapts - Determines how many additional random points are generated per input point.

Type type - ⊞ - Determines the random type.

Constant constant -

Two Values twovalues -

Uniform (Continuous) uniform -

Uniform (Discrete) uniformdiscrete -

Direction direction -

Inside Sphere insidesphere -

Normal (Gaussian) normal -

Exponential exponential -

Log-Normal lognormal -

Cauchy-Lorentz cauchylorentz -

Custom Ramp customramp -

None none -

Gaussian (Normal) gaussian -

CHOP chop - When the distribution type is Custom Ramp, the CHOP to use for the custom ramp.

Random Size randomsize - ⊞ - Number of random components.

1 1 -

2 2 -

3 3 -

4 4 -

Seed seed - Numerical value that initializes the randomization.

Parameter Size parsize - ⊞ - Number of independent configurable parameter values.

1 1 -

2 2 -

3 3 -

4 4 -

Amplitude amp - For certain types of random values, the random values amplitude (a scale on the values output).

Exponent exp - Sets the exponent. The internal value is raised by the power of the exponent

Offset offset - Adds an offset to the resulting value.

Value A valuea - One of two values determining the random numbers that are output.

Value B valueb - One of two values determining the random numbers that are output.

Value B Probability valuebproba - The probability that the numbers will be biased toward value B vs A.

Clamp Value clamp - Whether to clamp the output value between a minimum and a maximum.

Clamp Min minval - Minimum output value.

Clamp Max maxval - Maximum output value.

Cone Direction conedir - ⊞ - When random distribution is direction, specifies the cone direction.

Cone Direction conedirx -

Cone Direction conediry -

Cone Direction conedirz -

Cone Angle coneangle - When random distribution is direction, specifies the cone angle around the cone direction.

Combine Operation combineop - ⊞ - Specify how to combine the output value with the combine attribute value.

Set set -

Add add -

Multiply mult -

Translate along Normal translatealongnormal -

Combine Attribute Scope combineattrscope - Input attribute scope for the combine operation.

Output Attribute Scope outputattrscope - ⊞ - Name of attribute to output (can choose components of attribute), can choose from menu.

P P -

N N -

Color Color -

Color.rgb Color.rgb -

Tex Tex -

PointScale PointScale -

LineWidth LineWidth -

Override Automatic Attribute overrideautoattr - Whether to override the kind of attribute automatically created based on the POP input and parameters. Allows to specify manually the type and number of components of the new attribute.

Attribute Type attrtype - ⊞ - The output attribute's data type, default float.

float float -

double double -

int int -

uint uint -

Color color -

Color (double) dcolor -

Direction dir -

Direction (double) ddir -

Components attrnumcomps - ⊞ - The number of components in the new custom attribute.

1 1 -

2 2 -

3 3 -

4 4 -

Default Value attrdefaultval - ⊞ - Default values of the output attribute components if they cannot be computed.

Default Value attrdefaultval0 - Default value(s) of the attribute.

Default Value attrdefaultval1 - Default value(s) of the attribute.

Default Value attrdefaultval2 - Default value(s) of the attribute.

Default Value attrdefaultval3 - Default value(s) of the attribute.

Attribute Class attrclass - ⊞ - Makes the POP operate on point attributes, vertex attributes or primitive attributes where applicable.

Point point -

Vertex vertex -

Primitive primitive -

Group group - If there are input groups, specifying a group name in this field will cause this POP to act only upon the group specified.

Compute Point Normals computenormals - Whether to compute point normals as a post operation.

Parameters - Map Page

Mapping map - Start of Sequential Parameter Blocks for attribute-to-parameter mapping.

OP map0op - Source OP for parameter mapping. The default of _in0 means the input POP.

Element map0element - The attribute (or component of an attribute) that will be mapped to a parameter per-point.

Parameter map0parm - ⊞ - Parameter on the current POP that will be mapped from the Element (the attribute).

amp (Amplitude) amp -

exp (Exponent) exp -

offset (Offset) offset -

valuea (Value A) valuea -

valueb (Value B) valueb -

valuebproba (Value B Probability) valuebproba -

stepval (Step Value) stepval - The minimum difference between two random values for uniform discrete mode.

minval (Clamp Min) minval -

maxval (Clamp Max) maxval -

conedir (Cone Direction) conedir -

conedirx conedirx -

conediry conediry -

conedirz conedirz -

coneangle (Cone Angle) coneangle -

Combine Operation map0combineop - ⊞ - Combine operation for attribute value with parameter value.

Set set -

Multiply mult -

Add add -

Parameters - Common Page

Bypass bypass - Pass through the first input to the output unchanged.

Free Extra GPU Memory freeextragpumem - Free memory that has accumulated when output memory has grown and shrunk.

Delete Input Attributes delinputattrs - Only output which attributes you specify in this POP - helps isolate attributes into a separate branch.

Operator Inputs

Input 0: -

Info CHOP Channels

Extra Information for the Random POP can be accessed via an Info CHOP.

Common POP Info Channels

Common Operator Info Channels

total_cooks - Number of times the operator has cooked since the process started.

cook_time - Duration of the last cook in milliseconds.

cook_frame - Frame number when this operator was last cooked relative to the component timeline.

cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.

cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.

cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.

cooked_this_frame - 1 if operator was cooked this frame.

warnings - Number of warnings in this operator if any.

errors - Number of errors in this operator if any.

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