Houdini 13.0 Nodes

interface version 1

Creates a new attribute by mapping a point attribute to a ramp.

Parameters

Point Group

The group of points the operator affects.

Input Attribute

Name of the attribute that drives the mapping.

This field supports several “pseudo-attributes” (using an “auto:” prefix – e.g. auto:ageNormalized stands for normalized particle age). See below for more details.

Signature, Component

Signature of the output attribute (float, vector, integer), and component for vector attributes (X, Y, Z, length).

Input Min, Max

Minimum and maximum values of the input that fit to the start end end of the ramp.

By pressing the Get button the corresponding (min/max) value will be determined from the actual attribute values, and it will be written into the parameter field.

If a value field is disabled, its value will be determined automatically from the attribute values. (These min/max calculations are redone whenever the input attributes change.)

Input Exponent

An exponent (“gamma”) applied to the input value (after it’s normalized in the [0..1] range).

Wrap

How to apply the ramp to values outside the specified input min/max range.

Streak

For outside-range values, the ramp’s nearest endpoint values will be used.

Repeat

The ramp will be applied to outside-range values, producing a repeating pattern.

Zig-Zag

Same as Repeat, but in an alternating fashion (every 2nd repeat pattern is reversed).

...

Output

Name of the attribute that stores the result of the mapping.

Operation

Type of operation. The original value of the output attribute can be added, multiplied or be replaced with the result.

Color Mode

Color mode of the ramp.

Ramp

The ramp that gets mapped.

Exponent

Exponent of a power operation that allows you to make a gamma correction of the output.

Auto-Attributes

Auto-attributes are not actual geometry attributes, but values generated from existing geometry information – usually something that is trivial. fast to compute, and would be wasteful to store as a separate attribute. *

The following auto-attributes are available –

auto:ageNormalized

Particle age, normalized in the [0..1] range. Requires particle life attribute(s) to be present.

auto:ptnum

Geometry point index. (To have a normalized value, use the expression npoints(opinputpath("..", 1)) in the Input Max field.)

Note

Automatic value range detection doesn’t work for auto-attributes.

* – The classic “CPU vs memory” problem. In this case, experience shows that with massive amounts of geometry (e.g. tens of millions of disk-cached particles) it’s best to compute as much as possible (as opposed to store). Even a single attribute can make quite a difference.

Todo

  • Out-of-range mapping (keep, repeat, output-black (?)).

Release Notes

interface version 1 —

2014-02-11

  • Enhanced attribute selection menu

  • Default composite operation is now “Replace”

  • Other minor UI changes

2013-10-01

  • Added (optional) Output Range correction fields (floats for vector mode as well, i.e. amplitude)

2013-09-15

  • Added presets for Output Exponent

  • Added Wrap parameter

2013-08-14

  • Added more items to the Output attribute presets menu.

2013-05-23

  • Added convenience auto: pseudo-attribute support (e.g. normalized particle age, etc.)

  • Major speedup (can be even ~50%) when not using automatic attribute range detection

2013-04-07

  • Re-created all ramp parameters (they were crashing H12.5 for some reason).

2013-02-18

  • Added 'local variable' field for output attribute

2013-02-12

  • Support for integer input attributes

  • Supports both automatic and manual range detection

2012-08-02

Initial release.