# gleLathe.3gle man page

gleLathe — Sweep using a Z-axis shear to create an arbitrary contour along a helical path.

## Syntax

```
void gleLathe (int ncp,
gleDouble contour[][2],
gleDouble cont_normal[][2],
gleDouble up[3],
gleDouble startRadius, /* spiral starts in x-y plane */
gleDouble drdTheta, /* change in radius per revolution */
gleDouble startZ, /* starting z value */
gleDouble dzdTheta, /* change in Z per revolution */
gleDouble startXform[2][3], /* starting contour affine xform */
gleDouble dXformdTheta[2][3], /* tangent change xform per revoln */
gleDouble startTheta, /* start angle in x-y plane */
gleDouble sweepTheta); /* degrees to spiral around */
```

## Arguments

*ncp*- number of contour points
*contour*- 2D contour
*cont_normal*- 2D contour normals
*up*- up vector for contour
*startRadius*- spiral starts in x-y plane
*drdTheta*- change in radius per revolution
*startZ*- starting z value
*dzdTheta*- change in Z per revolution
*startXform*- starting contour affine transformation
*dXformdTheta*- tangent change xform per revolution
*startTheta*- start angle in x-y plane
*sweepTheta*- degrees to spiral around

## Description

Sweep an arbitrary contour along a helical path. The sweep will be performed as a shear along the z-axis, so that the orientation of the contour is displaced, rather than translated, as the contour is swept.

The axis of the helix lies along the modeling coordinate z-axis.

An affine transform can be applied as the contour is swept. For most ordinary usage, the affines should be given as NULL.

## See Also

gleSpiral

## Author

Linas Vepstas (linas@linas.org)