sur_approx - Geometric procedure

Creates a surface


Description

The function approximates a given surface (for instance a Consurf surface) to a new surface type (for instance to a bicubic surface or to facettes).

Syntax

sur_approx(id, ref, s_type, method, extra1, extra2:attributes);

REF	id;
REF	ref;
STRING	s_type;
INT	method;
FLOAT	extra1;
FLOAT	extra2;

Principal parameters

id	- Local identity
ref	- Surface that shall be approximated
s_type	- Output surface type
	CUB_SUR Bicubic surface
	FAC_SUR Facettes (B-planes)
	RAT_SUR Not yet implemented ....
	LFT_SUR Not yet implemented ....
	BOX_SUR Bounding box (six FAC_PAT's) for the surface
	BOX_PAT Patch bounding boxes
	NURB_SUR 4:th order B-spline surface
method	- Approximation method
	Eq. 1:   Number of patches is defined by extra1 and extra2
	Eq. 2:   The function calculates the necessary number of patches for the
	tolerances extra1 and extra2
	Eq. 3:   Number of patches is defined by extra1 and offset by extra2
	(only implemented for the FAC_SUR approximation)
	Eq. 11: As method= 1 but with double facettes
	Eq. 12: As method= 2 but with double facettes
	Eq. 13: As method= 3 but with double
extra1	- Number of facettes in U direction, in U and V direction or coordinate tolerance

Optional parameters

extra2

- Number of facettes in V direction, offset distance or surface normal tolerance

Attributes

PEN	- Pen or colour number
LEVEL	- Level number
BLANK	- Visible (0) or invisible (1)
SFONT	- Solid boundary and dashed midcurves (0)
SDASHL	- Dashlength

Example

sur_approx(#3, #2, "CUB_SUR", 1, 5);

Creates a new bicubic surface #3, with five new patches in the U direction and in the V direction, i.e. there will be 25 new patches for each patch in the original surface #2. There are no checks of tolerances for this case.