Houdini 19.0 Nodes Geometry nodes Attribute VOP

Attribute VOP geometry node

Runs a VOP network to modify geometry attributes.

Since 12.5

Double-click this node to build a VOP network inside. (Alternatively, you can specify a SHOP node containing the VOP network, or specify a .vfl file containing the CVEX program.)

Note

The VOP network runs in the CVEX context, not the SOP context. This means SOP specific VOPs and VEX operations are not available. Instead use the From File variants and the provided operator input strings.

This node modifies geometry attributes.

Create Parameter VOPs with the names of attributes to specify inputs. Set a parameter as “exported” to allow writing to/creating the corresponding attribute.

Parameters

Vex Setup

VEX Source

Where to get the program to modify attributes.

Myself

Use a VOP network inside this node.

SHOP

Use SHOP node containing a CVEX VOP network. Specify the node in the SHOP path parameter.

This can also point to any node that contains a CVEX VOP Network.

Note

Referenced nodes parameters will be used.

Script

Use a file containing a CVEX program. Specify the file path in the Script parameter.

SHOP Path

A SHOP node containing a CVEX VOP network, when VEX source is SHOP.

Script

A path to a file containing a CVEX script, when VEX source is Script.

Re-load VEX Functions

When VEX source is Script, reloads any .vex files to account for changes made outside of Houdini.

Compiler

When VEX source is Myself, the command line Houdini uses to compile the VOP network inside this node.

Force Compile

When VEX source is Myself, recompiles the VOP network inside this node.

Evaluation Node Path

VEX functions like ch() usually evaluate with respect to this node. Enter a node path here to override where the path search starts from. This is useful for embedding in a digital asset, where you want searches to start from the asset root.

Export Parameters

When a VEX parameter is exported, the bound attribute will be created if it doesn’t exist. This pattern can be used to override the export option on the VEX shader to avoid writing to or creating certain attributes. The pattern matches the VEX parameter, not the bound attribute. The attribute will still be bound for reading.

Enable Multithreading

There should be no threading issues with VEX. In the unlikely event that there are, this will allow you to determine which node is guilty, and work around it without turning off threading on a global scale.

Data Bindings

VEX Precision

VEX can evaluate at 32-bit or 64-bit precision. 64-bit provides higher accuracy, especially for transforms.

Note

Incoming attributes will preserve their original precision, so using 64-bit VEX on 32-bit positions will convert them to 64-bit, apply the operation, then convert back to 32-bit when writing out.

The auto mode will switch between 32-bit and 64-bit depending on the preferred precision of the incoming geometry. When run in 64-bit precision, any created attributes will be 64-bit. When run in 32-bit any created attributes will be 32-bit. Use Attribute Cast to change the preferred precision.

Group

Only run the VOP network on this group in the input geometry. Leave this blank to modify all the input geometry.

Group Type

What the group is made of.

/nodes/sop/Include_run_over

Autobind by Name

Automatically bind attributes to parameters by name. If for some reason you need CVEX parameters to have different names than the corresponding attributes, turn this off and use the Number of bindings parameter to set up mappings between Attribute name and VEX parameter.

Integer attributes will bind to integer parameters. Float attributes will bind to float, vector, point, matrix, or matrix4 depending on their tuple size. String attributes will bind to strings.

Autobind Groups by Name

Automatically bind any groups to the integer parameter prefixed with group_.

Update Normals If Displaced

If points are being run over, and the P attribute is written to, but the N attribute is not written to, any incoming normals will become out of date. When this option is set, vertex and point normals will be updated when this occurs.

Attribute to Match

The @opinputinputnum_name syntax lets you get the value of an attribute from the corresponding element on another input. If this parameter is blank, the “corresponding” element is the element with the same index (e.g. point number) as the element the node is currently processing. If you specify the name of an attribute, the “corresponding” element is the element that has the same value in the named attribute as the current element. See accessing attributes from other inputs on the VEX snippets page for more information.

For example, if you used id as the “attribute to match”, and you were processing a point with attribute id set to 12, then @opinput1_P would give you the P attribute on the point in the second input that also has id set to 12.

Compute Results In Place

When compiled the Attribute VOP is able to work on the incoming geometry in place without making a copy of it. This can speed up processing as one less copy is made, but requires that the VEX code doesn’t bind for writing any attributes that are read from the first input.

Output Selection Group

The name of a group to use as the output selection. When the highlight flag is enabled for this node, this group will be the output selection used by later modeling tools (if it exists).

See also

Attribute VOP