# Warping

Warping indicates that a face is not planar and is applied only to 2D elements with 4 nodes. This quality control criterion is based on a projection plane created by:

1. bisecting the four element edges,

2. creating a point on the plane at the vector average of the corners, where the x-axis extends from the point to the bisector on edge 2.

The plane normal is in the direction of the cross product of the x-axis and the vector from the origin to the bisector of edge 3. Every corner of the quad will then be a distance “h” from the plane. The length of each half edge is measured and the shortest length is assigned “l”. The warp angle is the arcsine of the ratio of the projection height “h” to the half edge length “l”.

To apply the Warping quality criterion to your mesh:

1. Display your mesh in the viewer.

2. Choose Controls > Warp or click button of the toolbar. Your mesh will be displayed in the viewer with its elements colored according to the applied mesh quality control criterion:

See Also a sample TUI Script of a Warping quality control operation.