Curvature Evaluation
The visual quality of a line can be evaluated using a curvature locator (shown in green below). This can be applied to curves, surface edges, and isoparms, as well as to section lines through a surface.
The Curve Curvature tool is a locator and so it's a temporary visual evaluation tool.
The curvature value is the inverse of the radius at any one point (C=1/R). This calculation is displayed graphically at discreet points along the curve.
- The length of each green curvature line is proportional to the inverse of the radius of the curve at that point. The actual length is user defined and is selected to suit the geometry being evaluated.
- The direction of each curvature line is at 90 degrees (normal) to the curve at each point.
- The red outline is a visual aid to help evaluate the flow of curvature change.
Tools
The following tools can be used to display and evaluate curvature:
- Control Panel > Curvature
- Curve Curvature
- Delete > Locators
- Pick Locator
- Cross-Section Editor
- Information Window (to change locator settings).
Deep dive: Interpreting curvature combs
The curvature comb plots are interpreted by the change in line length as you look along the curve from start to end.
- A constant length of comb indicates a constant radius, for example an arc.
- A changing comb length indicates acceleration or deceleration of the curve shape.
- Inflections are shown by the combs switching sides and optionally by an additional red arrow indicator.
- Breaks in the red boundary curves indicate curvature discrepancies across edit points or between two curves.
Deep dive: Curvature combs and continuity
Curvature comb plots can be used to evaluate the continuity between two adjacent curves or surfaces.
- G0 Position - Curvature plots are at an angle.
- G1 Tangent - Curvature plots are aligned but radius values are different.
- G2 Curvature - Curvature plots are aligned and radius values are the same.
- G3 Curvature - As above, and the curvature plot outlines (red curves) are G1 tangent.
Deep dive: Surface curvature evaluation
Surface curvature is more complex to use and interpret than curve curvature as the direction you choose to measure in affects the feedback.
See Windows > Diagnostic Shade and Evaluation > Curvature for more information. See also: Class A tutorials: 2.8 Surface Curvature Shading Analysis
In the illustration below, the curve curvature and surface curvature (principal max.) are applied to the surfaces:
