GLdoublevalueX, GLdoublevalueY, GLdoublevalueZ)

**eqn not supported**

*tess*- Specifies the tessellation object (created
with
**gluNewTess**). *valueX*- Specifies the first component of the normal.
*valueY*- Specifies the second component of the normal.
*valueZ*- Specifies the third component of the normal.

If the supplied normal is (0.0, 0.0, 0.0) (the initial value), the normal is determined as follows. The direction of the normal, up to its sign, is found by fitting a plane to the vertices, without regard to how the vertices are connected. It is expected that the input data lies approximately in the plane; otherwise, projection perpendicular to one of the three coordinate axes may substantially change the geometry. The sign of the normal is chosen so that the sum of the signed areas of all input contours is nonnegative (where a CCW contour has positive area).

The supplied normal persists until
it is changed by another call to **gluTessNormal**.