Attribute Transfer particle node
Transfers point or vertex attributes from reference geometry onto particles.
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.
Using Attribute Transfer
Set up the attributes on your geometry.
Click the
Attribute Transfer button on the Drive Particles tab.Click
the 
particle system you want to be affected and press Enter to confirm your selection.Click
the object you want the particles to affect and press Enter to confirm your selection.Set SOP in the parameter editor to the node you want to transfer attributes from.
On the Attributes tab in the parameter editor, list the attributes you want to transfer. If the field is left blank , all of the node’s attributes will be transferred.
On the Conditions tab in the parameter editor, set the Distance Threshold to specify how close the particles must be to the object before the attributes are transferred.
Parameters
Activation | Turns this node on and off. The operator is only active if this value is greater than 0. This is useful to control the effect of this node with an expression. | ||||||||||
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.
| ||||||||||
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
|
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 carat character (
^).If the first attribute is preceded by a carat (
^), 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® = Sum(over all j) (m[j] A[j]/p[j] Wh(r-r[j]) …where r is a position in space, Wh is a normalized smoothing kernel over a radius h, and m[j], A[j], p[j], r[j] 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 drop-off 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. |
| 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 | Non-uniform 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. |
| 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 lower-left 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 up-vector 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. |
Examples
The following examples are specifically designed to demonstrate this node:
Color
$HFS/mozilla/documents/examples/nodes/pop/attribtransfer/Color.cmd
The following examples use this node:
DrainExample
$HFS/mozilla/documents/examples/nodes/dop/particlefluidemitter/DrainExample.otl
DrainExample
$HFS/mozilla/documents/examples/nodes/dop/particlefluidemitter/DrainExample.otl
PressureExample
$HFS/mozilla/documents/examples/nodes/dop/particlefluidsolver/PressureExample.otl
PressureExample
$HFS/mozilla/documents/examples/nodes/dop/particlefluidsolver/PressureExample.otl
VolumeSource
$HFS/mozilla/documents/examples/nodes/dop/particlefluidemitter/VolumeSource.otl