|On this page|
The Noise CHOP makes an irregular wave that never repeats, with values
approximately in the range
+1. It appears to have a period like
the Wave CHOP, but it is not exact. It generates both smooth curves and
noise that is random each sample. It uses the same math as the Noise
Optionally, an input can be connected. It is assumed that the input contains 1 to 3 channels representing X, Y and Z coordinates of points in space, and are used to sample anywhere in 3D noise space. One index in the input produces one sample in the output.
*Optional input: XYZ sample points*
Normally the noise is sampled along the X-axis in an XYZ noise space. You can sample anywhere in XYZ.
The noise function used to generate noise.
Produces high quality, continuous noise.
Produces lower quality noise than Sparse, but quicker.
Sparse noise with the ability to control the frequency step of the harmonics.
Produces "Brownian" motion, similar to insect flight.
Every sample is random and unrelated to any other sample. Also know as "white noise" in audio.
Any number, integer or non-integer. Each number generates completely different noise patterns, but with similar characteristics.
The approximate separation between peaks of a noise cycle, expressed in Units.
The number of higher frequency components to layer on top of the base frequency.
The factor by which the frequency of the harmonics are increased.
The amount of the effect of the higher frequency harmonics.
Pushes the noise values toward
-1 (raising the
noise to the this power).
Num of Integrals
The number of times to integrate Brownian noise, which affects its smoothness.
The noise’s amplitude.
Ensures that all noise curves fall between
Allows the noise curve to start and/or end at selected values. The average value may also be constrained.
The value noise curves should start at.
THe value noise curves should end at.
The mean value noise curves should have.
The names of the channels to be created.
Indicates how much of the channel to cook.
Use Full Animation Range
All of the current global animation range.
Use Current Frame
Only the sample at the current frame.
Specify the range using the Start/End parameters.
The start of the channels.
The end of the channels.
The sample rate of the channels.
The left extend conditions of the channels.
The right extend conditions of the channels.
The default value for extend conditions.
Some of these parameters may not be available on all CHOP nodes.
To determine which channels get affected, some CHOPs have a scope string. Patterns can be used in the scope, for example
* (match all), and
? (match single character).
The following are examples of possible channel name matching options:
Matches a single channel name.
chan3 tx ty tz
Matches four channel names, separated by spaces.
Matches each channel that starts with
Matches each channel that has
foot in it.
? matches a single character.
t? matches two-character channels starting with t.
Matches number ranges giving
[xyz]matches three characters, giving channels
Sample Rate Match
The Sample Rate Match Options handle cases where multiple input CHOPs’ sample rates are different.
Resample At First Input’s Rate
Use rate of first input to resample others.
Resample At Maximum Rate
Resample to highest sample rate.
Resample At Minimum Rate
Resample to the lowest sample rate.
Error if Rates Differ
Does not accept conflicting sample rates.
The units for which time parameters are specified.
For example, you can specify the amount of time a lag should last for in seconds (default), frames (at the Houdini FPS), or samples (in the CHOP’s sample rate).
When you change the Units parameter, it does not convert the existing parameters to the new units.
Time Slicing is a feature which boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel does need to be evaluated every frame, then cooking the entire range of the channel is unnecessary. It is more efficient to calculate only the fraction of the channel that is needed. This fraction is known as a Time Slice.
Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.
The Export prefix is prepended to CHOP channel names to determine where to export to.
For example, if the CHOP channel was named
geo1:tx, and the prefix was
/obj, the channel would be exported to
You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as
Every CHOP has this option. Each CHOP gets a default color assigned for display in the Graph port, but you can override the color in the Common page under Graph Color. There are 36 RGB color combinations in the Palette.
Graph Color Step
When the graph displays the animation curves and a CHOP has two or more channels, this defines the difference in color from one channel to the next, giving a rainbow spectrum of colors.
The current index.
The current channel (0 to NC-1).
The total number of channels.
The start and end indices of the noise curve.