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This operator transfers attributes (such as normal direction) from some referenced geometry to the input particles.
Vertex attributes are changed to point attributes for the particles if necessary. All vertices referencing a particular point are considered a single sample and the value of the first one is used as the sample value.
You can choose which attributes are transferred with patterns in the Points and Vertices parameters on the Attributes tab.
This operator can use two different methods for controlling when and how attributes are transferred, controlled in the Conditions tab.
Parameters
Activation
Turns this node on and off. The node is only active if this value is greater than 0. This is useful to control the effect of this node with an expression.
Note that this is activation of the node as a whole. You can’t use this parameter to deactivate the node for certain particles.
Source Group
Only affect a group of points (created with, for example, a Group POP or Collision POP) out of all the points in the input.
Geometry Source
Specifies the SOP to use.
Use Parameter Values
Use the SOP specified in the SOP parameter below.
Use First Context Geometry
Use the SOP connected to the POP network’s first input.
Use Second Context Geometry
Use the SOP connected to the POP network’s second input.
Use Third Context Geometry
Use the SOP connected to the POP network’s third input.
Use Fourth Context Geometry
Use the SOP connected to the POP network’s fourth input.
SOP
Path to the SOP (when Geometry source is set to Use Parameter Values).
Ignore Transform Object
Particles normally use the object space of the SOP being cooked. Turn this parameter on to not transform into the space of the cooking SOP.
SOP Group
Subset of the referenced geometry to use. Either a group pattern or a named group (created by a Group SOP) can be used.
SOP Group Type
How to interpret the SOP Group parameter
Primitives
Interpret the string as a primitive group.
Points
Interpret the string as a point group.
Attributes
Choose which attributes are transferred with patterns in the Points and Vertices parameters.

To transfer all available attributes, leave the field blank or set it to a single asterisk (
*
). 
To exclude attributes, prefix an attribute name with the caret character (
^
). 
If the first attribute is preceded by a caret (
^
), all attributes are assumed to be transferred except where explicitly excluded. Otherwise, no attributes are assumed except where explicitly included.
Points
List of names/patterns of point attributes to transfer. Turn off the checkbox to avoid transferring any point attributes.
Vertices
List of names/patterns of vertex attributes to transfer. Turn off the checkbox to avoid transferring any vertex attributes.
Conditions
This tab lets you choose between two methods (Weighted average and Smoothed particle sampling) to control when and how attributes are transferred.
This tab displays different parameters depending on which method you choose.
Weighted average
Destination attributes are interpolated from the source attributes using a weighted proximity technique. Attribute calculations use the distance between the destination point and the candidate source points.
Smoothed particle sampling
This mode is based on the SPH (Smoothed Particle Hydrodynamics) model. This is a specialized model of attribute transfer useful in certain technical situations.
Each attribute is sampled using the formula:
A(r) = Sum(over all j) (m\[j] * A\[j]/p\[j] * Wh(rr\[j])
…where r is a position in space, Wh is a
normalized smoothing kernel over a radius h, and
mj
, Aj
, pj
, rj
are the mass,
attribute value, density, and position of sample j.
You might want to use the SPH model when you need to sample some physical quantity (say, temperature) at an arbitrary location in a space (generally a gas, liquid, or solid volume) and you have a discrete sampling of that quantity.
You would not use it when doing things such as grabbing colors from geometry, but you might want to use it if, for example, you are estimating a force vector within a wind tunnel at an arbitrary point given some spatial sampling of the force field.
Weighted average
Kernel Function
Interpolating metaball kernel . The kernels are parameterized by distance and typically give more weight to samples that are closer.
Kernel Radius
Radial extent of the kernel function. Specifies the dropoff radius for the kernel function. As the kernel radius parameter approaches zero, the filter resembles nearest neighbor interpolation. As the kernel radius parameter increases, the filter approaches uniform weighting.
Max Sample Count
Number of closest samples to interpolate from. specifies the maximum number of samples to interpolate from. A maximum sample count of 1 gives nearest neighbor interpolation.
Distance Threshold
Radial extent of the filter domain where the final attributes are determined from the source selection only. Specifies the maximum distance source points must be to be considered. Turning off this option indicates that no points/vertices will be excluded based on distance.
Initialize Attributes to Zero
Zero attributes when there are no samples. Attributes will be set to zero if no samples are found, otherwise, the attribute will maintain the previous value.
Smoothed particle sampling
SPH Kernel Function
Normalized smoothing function. Specifies the normalized smoothing kernel to use.
SPH Kernel Radius
The extent over which the samples are smoothed. Samples outside this radius do not contribute. specifies the maximum distance over which the kernel acts. The actual radius h used above is computed based on this value for each kernel.
Coefficient Attribute
An attribute that is used as a coefficient of the term
for a sample in the sum. Specifies the name of the point
attribute on the sample geometry to use as the
m[j]/p[j]
factor in the SPH formula.
Locals
Standard POP local variables
AGE
The seconds a particle in the template has been alive.
AX AY AZ
Acceleration of the particle.
BBX BBY BBZ
The point’s relative position in the bounding box.
DEAD
Point is dead.
ITER
Processing iteration number.
JUSTHIT
A collision for this particle was detected (for example, by the Collision POP) during the processing of this timestep (that is, this iteration of the particle simulation). This variable is cleared at the beginning of each timestep. Note that the collision POP actually detects any collisions which would have occurred the during the previous frame.
LIFE
Percent of total life used (from 0 to 1).
LIFESPAN
Expected lifetime of particle.
MAPU MAPV MAPW
Point or vertex texture coordinates.
NPT
Total number of points.
NGRP
Total number of points in source group.
NX NY NZ
Normal vector.
PT
The point number of the currently processed point. The PT
is not constant like ID
; it changes based on the number of points.
RESTX RESTY RESTZ
The rest position.
SLIDING
The sliding state of the particle.
SPRINGK
Elasticity of a point.
STOPPED
Point is stopped.
STUCK
1 if particle is stuck to a collision object.
TENSION
Spring tension.
TIMEINC
Time increment.
TX TY TZ
Point position.
U V
Surface UV values.
VX VY VZ
Velocity direction.
WEIGHT
Point spline weight.
Added by Collision POP/Limit POP
DIST
Distance from particle to last collision.
HCR HCG HCB
Diffuse color at the collision point on the surface the particle collided with.
HITID
ID for last collision. You can control how this attribute is set in the Collision or Limit POP to help distinguish types of collisions.
HITTIME
The time at which the last collision occurred.
HMAPU HMAPV
The texture map UV coordinates for the surface location where the last collision occurred.
HNX HNY HNZ
The normal at the surface location where the last collision occurred.
HTX HTY HTZ
World space position of the last collision.
HU HV
The UV coordinates for the surface location where the last collision occurred.
NUMHIT
Number of times the particle has collided.
Added by Color POP
CA
Point or vertex alpha value.
CR CG CB
Diffuse point or vertex color.
Added by Property POP
ATTRACT
Attractor point.
CHARGE
Charge of the particle.
CLING
Point is clinging to geometry.
DRAG
Point drag.
FOLLOW
Leader to follow.
MASS
Point mass.
PSCALE
Particle Scale.
SCALEX SCALEY SCALEZ
Nonuniform scale.
Added by Proximity POP
NEAREST
Either the point number or id of the particle nearest to this one.
NEARESTDIST
The distance to the nearest particle.
NUMPROXIMITY
The number of particles within a specified proximity to this particle.
Added by Rotation POP
ROTA
Rotation angle.
ROTX ROTY ROTZ
Rotation axis.
Added by Source POP
GEN
Generation.
ID
ID number, which always remains constant.
ORIGIN
Original Source point was birthed from.
PARENT
Parent’s ID Number.
Added by Speed Limit POP
SPEEDMAX
Maximum speed.
SPEEDMIN
Minimum speed.
Added by Sprite POP
SROT
Sprite rotation around view axis (in degrees).
STEXU STEXV
Texture coordinate of sprite’s lowerleft corner.
STEXW STEXH
Size of sprite in texture space.
SX SY
Sprite scale.
Controlled by Suppress Rule POP
SUPPPOS
Suppress default position rule.
SUPPVEL
Suppress default velocity rule.
SUPPUP
Suppress default upvector rule.
SUPPAGE
Suppress default aging rule.
SUPPROT
1 if particle is suppressing its default rotation rule.
SUPPANGVEL
1 if particle is suppressing its default angular velocity rule.
Added by Up Vector POP
PVX PVY PVZ
Previous velocity.
UPX UPY UPZ
Up vector.
Added by Location, Source, Softbody, Split POPs
SPEED
Absolute speed of particle.
See also 