debian man page for glespiral

gleSpiral(3GLE) 							GLE							   gleSpiral(3GLE)

NAME
       gleSpiral - Sweep an arbitrary contour along a helical path.

SYNTAX
       void gleSpiral (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 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.

       The "startXform[][]" is an affine matrix applied to the contour to deform the contour. Thus, "startXform" of the form

	    |  cos     sin    0   |
	    |  -sin    cos    0   |

       will rotate the contour (in the plane of the contour), while

	    |  1    0	 tx   |
	    |  0    1	 ty   |

       will translate the contour, and

	    |  sx    0	  0   |
	    |  0    sy	  0   |

       scales along the two axes of the contour. In particular, note that

	    |  1    0	 0   |
	    |  0    1	 0   |

       is the identity matrix.

       The  "dXformdTheta[][]"	is  a  differential  affine matrix that is integrated while the contour is extruded.  Note that this affine matrix
       lives in the tangent space, and so it should have the form of a generator.  Thus, dx/dt's of the form

	    |  0     r	  0   |
	    |  -r    0	  0   |

       rotate the the contour as it is extruded (r == 0 implies no rotation, r == 2*PI implies that the contour is rotated once, etc.), while

	    |  0    0	 tx   |
	    |  0    0	 ty   |

       translates the contour, and

	    |  sx    0	  0   |
	    |  0    sy	  0   |

       scales it. In particular, note that

	    |  0    0	 0   |
	    |  0    0	 0   |

       is the identity matrix -- i.e. the derivatives are zero, and therefore the integral is a constant.

SEE ALSO
       gleLathe

AUTHOR
       Linas Vepstas (linas@linas.org)

GLE
									3.0							   gleSpiral(3GLE)