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Curvature Direction

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Calculate the direction of maximum and minimum mesh curvature. The result is a vector that can be used for further operations such as Attribute Flow or point advection.

Images on this page use a simple point advection available in the examples file.

Types of Curvature Direction

Principled Curvature - Signed

Direction of maximum signed curvature: Across convex areas, along concave areas. Vectors can flip as the property is bi-directional.

  • Max Curvature

    edge_angle

  • Min Curvature

    mean

Principle Curvature - Unsigned

Direction of maximum unsigned curvature: Across both convex and concave areas. Prone to abrupt right angle changes. Vectors can flip as the property is bi-directional.

  • Max Curvature

    max

  • Min Curvature

    min

Change in Normals

Direction of change in neighboring normals. Produces a more swirly field that has a single direction (doesn't suffer from flipping).

  • Max Curvature

    max

  • Min Curvature

    min

Smoothing the Direction

The option to smooth input normals can be used to filter the scale of curvature to measure.

  • Unsmoothed Input Normals

    no_smoothing

  • Smoothed Input Normals

    smoothing

Outputs

  • Curvature Max Dir: Direction of maximum curvature.
  • Curvature Min Dir: Direction of minimum curvature.
  • Color: Direction of min/max curvature depending on debug settings.

Settings

  • Curvature: Type of curvature direction:
    • Principle Signed: Direction of maximum signed curvature: Across convex areas, along concave areas. Vectors can flip as the property is bi-directional.
    • Principle Unsigned: Direction of maximum unsigned curvature: Across both convex and concave areas. Prone to right angle changes. Vectors can flip as the property is bi-directional.
    • Change in Normals: Direction of change in neighboring normals. Produces a more swirly field that is immune from the bidirectional flipping issue.
  • Use Triangulated Mesh: Use a triangulated copy of the mesh to calculate curvature.
  • Smooth Normals: Iterations to smooth normals before calculating curvature direction.

Debug Views

  • Debug Direction:
    • Max: View maximum curvature direction.
    • Min: View minimum curvature direction.
  • Draw Debug Vectors.
  • Length: Length of displayed vectors.
  • Color: Output color attributes. Toggles outputting existing "Color" attribute or curvature direction. Remove output attribute to stop writing a color attribute.
  • Color Values:
    • Remapped 0-1: Remap values to 0-1 to view the full range as color. Areas of direction reversal visible.
    • Unchanged: Use curvature values directly as color. Areas of direction reversal visible.
    • Absolute: Absolute curvature direction. Ignores areas of direction reversal.