Noise SOP
Summary
The Noise SOP displaces geometry points using noise patterns. It uses the same math as the Noise CHOP.
Parameters  Noise Page
group
 If there are input groups, specifying a group name in this field will cause this SOP to act only upon the group specified. Accepts patterns, as described in Pattern Matching.
attribute
 ⊞  This menu sets which attribute of the geometry the Noise SOP acts on.
 Point Position
pos
 Noise is applied in the direction of the point normal. If no normal is specified, a normal is computed.
 Point Normals
n
 Noise is applied to each component of the normal independently and then the vector is renormalized.
 Point Diffuse Color
cd
 Noise is applied to each component of the color independently.
 Point Alpha
alpha
 Noise is applied to alpha.
 Point Texture UV
uv
 Noise is applied to each component uv independently.
 Point Texture W
w
 Noise is applied to texture w.
type
 ⊞  The noise function used to generate noise. The functions available are:
 Sparse
sparse
 Produces high quality, continuous noise based on Sparse Convolution.
 Hermite
hermite
 Quicker than Sparse, but produces lower quality noise.
 Harmomic Summation
harmonic
 Sparse noise with the ability to control the frequency step of the harmonics. Takes the longest to compute.
 Brownian
brownian
 Works like a bug in random flight. With Num of Integrals at 2, its acceleration is changed randomly every frame.
 Random
random
 (White Noise) Every sample is random and unrelated to any other sample. It is the same as "white noise" in audio.
 Alligator
alligator
 Cell Noise.
seed
 Any number, integer or noninteger, which starts the random number generator. Each number gives completely different noise patterns, but with similar characteristics.
period
 The approximate separation between peaks of a noise cycle. It is expressed in Units. Increasing the period stretches the noise pattern out.
Period is the opposite of frequency. If the period is 2 seconds, the base frequency is 0.5 cycles per second, or 0.5Hz for short. Hz refers to Hertz, the electrical and audio engineer of the 19th century, not the car guy.
If the Type is set to Random, setting this to zero will produce completely random noise. Otherwise, the period should be greater than zero.
harmon
 The number of higher frequency components to layer on top of the base frequency. The higher this number, the bumpier the noise will be (as long as roughness is not set to zero). 0 Harmonics give the base shape.
Harmonics with a base frequency of 0.1Hz will by default produce harmonics at 0.2Hz, 0.4Hz, 0.8Hz, etc. (up to the number of harmonics specified by the Harmonics parameter).
spread
 The factor by which the frequency of the harmonics are increased. It is normally 2. A spread of 3 and a base frequency of 0.1Hz will produce harmonics at 0.3Hz, 0.9Hz, 2.7Hz, etc.. This parameter is only valid for the Harmonic Summation type.
rough
 Controls the effect of the higher frequency noise. When Roughness is zero, all harmonics above the base frequency have no effect. At one, all harmonics are equal in amplitude to the base frequency. When Roughness is between one and zero, the amplitude of higher harmonics drops off exponentially from the base frequency.
The default roughness is 0.5. This means the amplitude of the first harmonic is 0.5 of the base frequency, the second is 0.25, the third is 0.125. The harmonics are added to the base to give the final shape. The Harmonics parameter and the Roughness parameter must both be nonzero to see the harmonic effects.
exp
 Pushes the noise values toward 0, or +1 and 1. (It raises the value to the power of the exponent.) Exponents greater than one will pull the channel toward zero, and powers less than one will pull peaks towards +1 and 1. It is used to reshape the channels.
numint
 Defines the number of times to integrate (see the Speed CHOP) the Brownian noise. Higher values produce smoother curves with fewer features. Values beyond 4 produce somewhat identical curves. This parameter is only valid for the Random noise type.
amp
 Defines the noise value's amplitude (a scale on the values output).
keepnormals

Parameters  Transform Page
The Translate, Rotate, Scale and Pivot parameters let you sample in a different part of the 3D noise space. Imagine a different noise value for every XYZ point in space. Normally, the Noise SOP samples the noise space from (0,0,0) along the Xaxis in steps of 2/period.
By changing the transform, you are translating, rotating and scaling the line along which the Noise SOPs samples the noise space. A slight Yrotation is like walking in a straight path in the mountains, recording your altitude along the way, then restarting from the same initial location, walking in a slightly different direction. Your altitude starts off being similar but then diverges.
xord
 ⊞  The menu attached to this parameter allows you to specify the order in which the transforms will take place. Changing the Transform order will change where things go much the same way as going a block and turning east gets you to a different place than turning east and then going a block.
 Scale Rotate Translate
srt

 Scale Translate Rotate
str

 Rotate Scale Translate
rst

 Rotate Translate Scale
rts

 Translate Scale Rotate
tsr

 Translate Rotate Scale
trs

rord
 ⊞  The rotational matrix presented when you click on this option allows you to set the transform order for the rotations. As with transform order (above), changing the order in which the rotations take place will alter the final position.
 Rx Ry Rz
xyz

 Rx Rz Ry
xzy

 Ry Rx Rz
yxz

 Ry Rz Rx
yzx

 Rz Rx Ry
zxy

 Rz Ry Rx
zyx

t
 ⊞  Translate the sampling plane through the noise space.
 X
tx

 Y
ty

 Z
tz

r
 ⊞  Rotate the sampling plane in the noise space.
 X
rx

 Y
ry

 Z
rz

s
 ⊞  Scale the sampling plane.
 X
sx

 Y
sy

 Z
sz

p
 ⊞  Control the pivot for the transform of the sampling plane.
 X
px

 Y
py

 Z
pz

Operator Inputs
 Input 0: 
Info CHOP Channels
Extra Information for the Noise SOP can be accessed via an Info CHOP.
Common SOP Info Channels
 num_points  Number of points in this SOP.
 num_prims  Number of primitives in this SOP.
 num_particles  Number of particles in this SOP.
 last_vbo_update_time  Time spent in another thread updating geometry data on the GPU from the SOP's CPU data. As it is part of another thread, this time is not part of the usual frame time.
 last_meta_vbo_update_time  Time spent in another thread updating meta surface geometry data (such as metaballs or nurbs) on the GPU from the SOP's CPU data. As it is part of another thread, this time is not part of the usual frame time.
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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