The calculate normals command serves to automatically calculate normals of an active object. The normal is a vector perpendicular to the object face surface. Is is used to calculate face lighting. The normal represents a direction in which must be located a light source for the face to be maximal lighted.

 

As a command parameter a maximal angle is entered that normals of different faces may hold in the contact vertex to be applied surface smoothing. The default angle value is equal to 0.5, i.e. 30 degrees approximately. Surface between faces with lower angle will be smoothed, i.e. ligting between faces will change smoothly. For faces with greater angle an unsmoothed normal will be used, a sharp edge will be observable between faces. By setting an angle to zero all smoothing will be switched off, a sharp edge will be observable between all faces. By setting to pi all face edges will be smoothed.