Houdini 17.0 Nodes VOP nodes

Ramp Parameter VOP node

Represents a user-editable ramp parameter.

On this page

The Ramp Parameter node represents a ramp user interface. The input specifies an index into the ramp. The value of the ramp at that position is the node’s output.

See the page on ramp parameters for more information on working with ramps.

Parameters

Name

The name of the new parameter, both in the VEX function declaration, the definition of any OP type that uses the VOPNET, and the VOP tile’s output. If a parameter by this name already exists, this operator will reference it and will disable most of of its own fields, such as the Parameter Type and Parameter Label.

The name must not be a reserved keyword.

Prefix

The optional prefix to prepend to the parameter name. The prefix changes the final name of the new parameter, both in the VEX function declaration, the definition of any OP type that uses the VOPNET, and the VOP tile’s output.

Postfix

The optional postfix to append to the parameter name. The postfix changes the final name of the new parameter, both in the VEX function declaration, the definition of any OP type that uses the VOPNET, and the VOP tile’s output.

Label

A human-readable label for this parameter. Appears in the parent node’s parameters and the tooltip when the user hovers over the output on the VOP tile.

Ramp Type

Whether this parameter is a color ramp (vector) or spline (float).

Color Type

The color space to use. This only applies to color ramps.

Default Interpolation

The default method for interpolating between ramp keys, for example "Linear" or "Constant". The user can change the interpolation method in the ramp interface, but this sets the default.

Use This Node to Set Parameter Attributes

When several Parameter VOPs have the same Parameter Name, only one of the nodes is used to control the attributes of the parameter. Houdini decides which node to use for this by searching all the nodes according to the user defined order, then traversing inside subnets. If none of them have this parameter turned on, the first one found is used to set the parameter attributes. If one or more do have this option turned on, the first one with this option is used, even if another node (with this option turned off) is found first.

Show UI Controls By Default

Control whether to show the ramp controls by default on the owner node’s parameter interface.

Help tab

The contents of the text field appear in the help browser when the user clicks the help button for a node of this operator type in the parameter editor.

This help can be HTML, or you can use a simple but powerful wiki format to create documentation that looks like the native Houdini help. See how to write wiki-format help.

Inputs

Position

The index into the ramp. The Ramp Parameter node outputs the value of the ramp at this position.

Outputs

Parameter

The value of the ramp at the position specified by the input to this node.

Examples

The following examples include this node.

DiffuseSmoke Example for Gas Diffuse dynamics node

This example demonstrates how to diffuse the density of a smoke simulation using the Gas Diffuse DOP.

grass

This example simulates grass being pushed down by an RBD object. Fur Objects are used to represent the blades of grass and Wire Objects are used to simulate the motion. When a single Fur Object is used to represent the grass, neighbouring blades of grass will have similar motion. Additional objects with different stiffness values can be used to make the motion less uniform. When "Complex Mode" is enabled, two objects are used to represent the grass. The stiffness of each set of curves can be controlled by adjusting the "Angular Spring Constant" and "Linear Spring Constant" parameters on the corresponding Wire Objects.

Clumping Example for Fur geometry node

The Fur SOP is used to instance hair-like curves.

In this case, the Fur SOP is used to create curves that can be used for clumping. A second Fur SOP is used to illustrate how to create hairs that use the clumping geometry.

FurBall Example for Fur geometry node

This example demonstrates how the Fur SOP builds hair-like curves based on guide curves and skin geometry.

FurPipelineExample Example for Fur geometry node

This example illustrates how custom shaders can be used to define the appearance of fur generated by the Fur SOP.

volumesurface_explicitgrade Example for Volume Surface geometry node

This example shows how to use the Volume Surface SOP to surface an SDF using another volume to specify the triangle sizes.

volumesurface_simple Example for Volume Surface geometry node

This example shows how to use the Volume Surface SOP to surface an SDF using adaptive triangle sizes.

RampParameter Example for Parameter VOP node

This example shows how to control the particle colours using the temperature attributes from a pyro simulation using a Ramp Parameter VOP node.

See also

VOP nodes