This page provides information on the V-Ray Curvature Map.
VRayCurvature is a texture that will effectively sample the underlying mesh for curves. A region around each shaded point gets sampled with additional rays (similar to VRayDirt) and all additional normals are averaged to get a smooth normal at the original point. This normal is used to compute the color. The color at each shaded point is a greyscale value: darker values are dents (or holes), lighter values are peaks. The parameters should be adjusted by trail and error since they generally depend on the scale used, hence the defaults might not be appropriate at all in some cases.
Subdivs – Controls the number of samples around each shaded point.
Sample spread – Controls the radius of the sampled region.
Min/Max Output Color – An option to map the output colors to a range other than 0..1.Makes the output texture darker or lighter.
Scale – Adjusts the scale relative to which the curvature is measured.
Threshold – Curvature values below this threshold are ignored and are shown as pure black. This focuses the curvature effect only around the most curved areas of the mesh.