Houdini 13.0 Nodes

interface version 2

Assigns attribute values based on a geometric shape.

This SOP generates per-component (point, primitive, vertex) geometry attribute values, using a 3D shape as a mask (either a built-in primitive, or a secondary geometry).

Generally it is used to create weight maps for other operators, such as deformers.

  • A scalar weight map (generated by Attrib Shape qL) used with a Weighted Transform qL SOP to pull at a certain geometry area. Attrib Shape is mostly used to generate scalar weight maps.

Parameters

Group

Name and class of a geometry component group to process.

Attribute

...

Class

Component class for the attribute (point, primitive, vertex, etc.)

Attribute

Name and type of the attribute.

Value (In, Out)

Attribute values for the inside and outside of the shape.

Switch Values

In is out and out is in. If on.

Falloff Exponent

An exponent value to be applied to the offset band (see below).

Composite

How to apply the values if the attribute already exists. (Replace, Add, Multply, Minimum, Maximum, Alpha Blend).

Source Attrib

Source attribute for composition. (Same as the output by default.)

Weight

Blend between original input and resulting attribute values.

Visualize

Display the results as a color gradient on the geometry. (Note that this shows only the current shape and ignores any source attribute values or composite operations.)

Note

This option generates an actual color (Cd) attribute on the geometry, apart from the actual output attribute. This is for visualization purposes only, don’t rely on it in any way (recommended to disable it if not needed any more).

Shape

Shape mask parameters.

Sphere, cylinder (superellipsoids), and box are provided as primitives (implemented as math equations).

The shape can also be regular geometry (it’s converted to an SDF volume so it should be “watertight” – i.e. closed shell(s)), or simply an SDF volume.

All shapes have an “offset band” – a soft falloff range from the In to the Out value.

Shape

The shape type.

Sphere

Sphere primitive (a superquad, actually). Has a single radius and offset band.

Cylinder

Cylinder primitive (with a superellipse profile). Has a single radius and two offsets (for radius and height). An infinite-height option is also provided.

Box

Regular box primitive. Has size and offset values for all three main axes.

Geometry, SDF Volume

Geometry or SDF volume, from the 2nd input.

Convert To

Volume type to convert geometry to.

(Use VDB. Regular might be a bit more tolerant of non-watertight shapes, but it’s way less efficient.)

Voxel Size

Voxel size for the resulting volume. (Note that the default value is intentionally large to avoid hanging accidents when connecting large geometry.)

Iso Value, Offset

SDF field values (surface threshold and “offset band”, or falloff).

Dither

Generate a grainy on-off pattern in the falloff areas instead of a smooth gradient.

Transform

Transformation of the mask shape. (Provides the full qLib-standard placement options.)

Examples

  • Visualizing the internal VDB-SDF volume generated for a custom shape (with red dots indicating voxel density).

  • A sphere shape with falloff and various ditherings (none, soft, sharp).

  • Generating per-primitive color attributes (Cd) using three Attrib Shape qL SOPs (blue box, orange sphere and green cylinder). Additive compositing is used; the cylinder has "infinite height" enabled.

To Do

  • Guide doesn’t show shape exponents

  • Z Exponent parameter doesn’t work right now (sphere mode)

  • uselocalvar/localvar doesn’t work

  • exponents/radii (sphere/cylinder) don’t work together properly (there’s difference between output and guide)

  • The 3d-space coords should be specifyable with an attribute (i.e. P by default, but could be rest, uv (!), etc) – however any attribute should work with any target class (point, prim, etc)

  • remove “Debug” switch after things work

  • “Unspecified” data type doesn’t work (and probably never will be...)

  • Add an “Over”-like Composite mode (Alpha Blend is a quick workaround right now)

  • ...

Release Notes

interface version 2 –

2014-10-06

  • Minor UI changes (a bit more compact layouts)

2014-06-23

  • Added “Alpha Blend” compositing mode (uses the In/Out values' alpha to blend with existing attrib values)

2014-03-28

  • Added some parameters to the viewport toolbox.

2014-03-25

  • Added Dithering mode

  • Added visualize color ramp presets (experimental, might not work)

2014-03-02

  • Fixed negative size offset issue with box primitive

  • Minor UI tweaks

2014-02-12

  • Minor UI tweaks

  • Descriptive parm

2014-02-11

  • Lots of issues ironed out

  • Guide geometry fixes and improvements

2014-02-09

First version.