sur_splarr - Geometric procedure

Creates a surface


Description

Creates a bicubic surface (patch type CUB_PAT) from points and tangents. Input data is given in 2-dimensional arrays.

The points are splined with the cur_spline() function. As an option tangents can be defined but unlike cur_spline() only the tangent directions are used and not the lengths of the tangents.

The created surface is continous in position and slope.


Syntax

sur_splarr(id, method, npu, npv, poi, utan, vtan, twist:attributes);

REF	id;
STRING	method;
INT	npu;
INT	npv;
VECTOR	poi( , );
VECTOR	utan( , );
VECTOR	vtan( , );
VECTOR	twist( , );

Principal parameters

id	- Local identity
method	- Defines the algorithm for the calculation of tangent lengths and twist vectors
	Eq. ZEROTWIST_1: All twist vectors will be zero
	Eq. ADINI_1: Twist vectors will be calculated with Adinis method
npu	- Number of points in the U direction
npv	- Number of points in the V direction
poi	- Array with points

Optional parameters

utan	- Array with normalized tangents in the U direction
vtan	- Array with normalized tangents in the V direction
twist	- Array with twist vectors

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

VECTOR poi(10,10);

sur_splarr(#3, "ZEROTWIST_1", 6, 4, poi);

Creates a new surface #3 defined by points in array poi. The number of CUB_PAT patches in the output surface will be 5 in U direction and 3 in V direction.

The order of the points in the array poi should be:

U= 0.0, V= 3.0                                                                                           U=5.0, V= 3.0

poi(1,4)	poi(2,4)	poi(3,4)	poi(4,4)	poi(5,4)	poi(6,4)
poi(1,3)	poi(2,3)	poi(3,3)	poi(4,3)	poi(5,3)	poi(6,3)
poi(1,2)	poi(2,2)	poi(3,2)	poi(4,2)	poi(5,2)	poi(6,2)
poi(1,1)	poi(2,1)	poi(3,1)	poi(4,1)	poi(5,1)	poi(6,1)

U= 0.0, V=0.0                                                                                            U= 5.0, V= 0.0