Computer Programs
NESC9602 CIRCLE SPLINE.
last modified: 28-JUL-1988 | catalog | categories | new | search |

# NESC9602 CIRCLE SPLINE.

#### CIRCLE-SPLINE, 2-D, 3-D Spline Curve Fitting

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1. NAME OR DESIGNATION OF PROGRAM:  CIRCLE SPLINE.
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2. COMPUTERS
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Program name Package id Status Status date
CIRCLE-SPLINE NESC9602/01 Tested 28-JUL-1988

Machines used:

Package ID Orig. computer Test computer
NESC9602/01 DEC VAX 11/780 DEC VAX 11/780
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3. DESCRIPTION OF PROGRAM OR FUNCTION

CIRCLE SPLINE is a library of routines used to generate splines in both two and three dimensions.  To use it, two subroutines, PTSMAK and PTSPAR must be called into a  main program to either generate or input the data that are to be interpolated by the CIRCLE SPLINE routine. Because of the multi- dimensional generation, the x-, y-, and z-coordinates must always be available. If a two-dimensional spline is desired, the third coordinate should be set to zero and run through the subroutine.
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4. METHOD OF SOLUTION

CIRCLE SPLINE generates a spline by constructing and connecting a series of circular arcs. Subroutine PTSMAK takes the coordinates of three successive data points, calculates the parametric location of the center of a circle of radius r, and places an arc through the three data points. Once the  first arc has been generated, PTSMAK moves by increments along the curve to the next data point. For N data points, N-2 arcs are produced. Two arcs pass between each pair of data points, with the exception of the two end pairs. CIRCLE SPLINE blends successive pairs of arcs to fit a single curve between data points. This blending process is performed by linearly weighing the effect each arc has in the interval between the respective data points. The user controls the number of subpoints that are between data points and available for the blending process.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The CIRCLE SPLINE blending process develops errors if too many subpoints are used, and persistent errors occur in cases of extreme variation of curvature (as in a cigar-shaped ellipse).
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6. TYPICAL RUNNING TIME:
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7. UNUSUAL FEATURES OF THE PROGRAM

Because of the circular configuration in which it fits data, CIRCLE SPLINE is well-suited to machining processes.
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8. RELATED AND AUXILIARY PROGRAMS

CIRCLE SPLINE uses the Los Alamos Common Graphics System CGS (PSR-0243) for plotting. CIRCLE SPLINE, which can be used effectively in both two and three dimensions, compares favorably with the Wilson-Fowler spline software - SPLPKG,  WFCMPR, WFAPPX (NESC 9736) - which can be used effectively only in two dimensions.
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9. STATUS
Package ID Status date Status
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10. REFERENCES:
NESC9602/01, included references:
- R.M. Dolin and D.L. Jaeger :
Examination of the Circle Spline Routine
LA-10521-MS UC-32 (November 1985)
- R.M. Dolin and W.R. Oakes :
A Comparison Between the Wilson-Fowler Spline and the Circle
Spline Routines
LA-10522-MS UC-32 (November 1985)
CIRCLE SPLINE Tape Directory and Implementation Information
NESC Note 87-42 (February 19, 1987)
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11. MACHINE REQUIREMENTS

At NEA-DB a Tektronix 4014 graphics display and a laser printer LN03 were used to test the program.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC9602/01 FORTRAN-77
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  VMS 4.4.
NESC9602/01
The program was tested at NEA-DB using the proprietary  graphics package DISSPLA of ISSCO.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHORS

R.M. Dolin
Analysis and Testing Group
Los Alamos National Laboratory
LOS ALAMOS, New Mexico. U. S. A.
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16. MATERIAL AVAILABLE
NESC9602/01
File name File description Records
NESC9602_01.001 INFORMATION FILE 72
NESC9602_01.002 SOURCE PROGRAM 490
NESC9602_01.003 VAX COMMAND PROCEDURE 10
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17. CATEGORIES
• P. General Mathematical and Computing System Routines

Keywords: data, interpolation, numerical solution, spline functions, three-dimensional, two-dimensional.