Houdini 21.0 Nodes Copernicus nodes

Curvature Copernicus node

Computes the curvature of a layer.

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Since 21.0

This node computes the curvature of the input layer. The node interprets the input layer as a height field (mono) or a normal vector field derived from a height field (RGB).

You can use this node for edge detection, similar to the Derivative COP. The node also helps detect and separate convex and concave regions.

Parameters

Signature

The layer type that the source accepts.

See Signatures for more information.

Method

The method used to calculate the layer’s curvature.

Finite Difference

Compute the difference between the current pixel value and its neighboring values. This uses classic definitions of curvature based on derivative values. This method is more stable than Angle Deficit for smooth inputs, such as a parameterization of hemisphere.

Angle Deficit

Treat each pixel as a vertex in a polygonal height field. This calculates the sum of the angles formed at each pixel by its neighboring vertices. The angle sum equals 2𝜋 in flat regions, but the sum is less in curved areas and results in an angle deficit that’s used to estimate local curvature. This method performs more robustly when the input includes complex or non-uniform variations.

Curvature Type

The curvature type from the input layer to compute.

Gaussian

This curvature is positive in both convex and concave regions. It becomes negative at saddle points, where the surface curves in opposite directions (concave in one direction and convex in the other). Gaussian curvature is useful for distinguishing simple convex and concave shapes from regions with saddle-like geometry.

Mean

This curvature is positive in convex regions and negative in concave regions. Mean curvature is useful for distinguishing convex, concave, and flat regions.

Principal (max)

The maximal principal curvature represents the largest normal curvature at a point. Although it’s not a direct measure of convexity, it often emphasizes geometrically prominent, outward-curving features.

Principal (min)

The minimal principal curvature represents the smallest normal curvature at a point. Although it’s not a direct measure of concavity, it often emphasizes geometrically recessed, inward-curving features.

Output Type

The values from the layer’s computed Curvature Type to output.

Curvature

Outputs the entire computed curvature.

Convexity

Outputs the convex regions based on the selected curvature.

Concavity

Outputs the concave regions based on the selected curvature.

Pre-process

Normal Type

When a normal vector field is generated by the Height to Normal COP, its type must be set to match that node.

See Normals for more information.

Signed

Output signed normals, compatible with geometry attributes.

Offset

Output offset normals, compatible with normal maps.

Scale

Adjusts the scale of the input’s pixel values.

Read Pixels outside Image

Adds contributions from pixels outside of the image to compute curvature at the image boundaries. This depends on the border type, which determines what pixels to read as outside of the image. If the boundary uses wrapping, the result is correct. If the boundary is constant, turn this parameter off to produce correct values near the edges.

Kernel Size

The scale of the neighborhood that the node considers for curvature computation at each pixel. A larger neighborhood often yields smoother curvature results.

Post-process

Scale

Adjusts the scale of the output’s pixel values.

Normalize

Normalizes the output result, which makes the output values stay in the 0 to 1 range. Since minor variations between neighboring pixels can result in unexpectedly high curvature values, this improves visualization by revealing the full curvature structure.

Minimum

The minimum value to clamp the curvature value to.

Maximum

The maximum value to clamp the curvature value to.

Inputs

source

The mono layer that represents a height field or the RGB layer that represents a normal field.

Outputs

curvature

The layer that stores the curvature values.

See also

Copernicus nodes