# gleLathe.3gle - Man Page

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)