Lesson of 20 July 2009 (morning)

Skeleton of a Simple vector/matrix library for 3d vector and 3x3 matrix (C style)

File lib3d.h

 1/*
 2  File: lib3d.h
 3  Simple vector/matrix library for 3d vector and 3x3 matrix.
 4*/
 5
 6/* first trick, avoid double inclusion using conditional compilation */
 7
 8/* check if LIB3D_H is defined, if NOT the lines up to #endif are expanded */
 9#ifndef LIB3D_H
10#define LIB3D_H // define an empty macro, only to define the symbol LIB3D_H
11
12#include <stdio.h>
13
14#ifdef __cplusplus
15extern "C" {
16#endif
17
18  /* valueType is the "real number" type */
19  typedef double valueType ;
20
21  /* A vector is a struct with 3 field, x y z */
22  /*
23  struct _point3d {
24    valueType x ;
25    valueType y ;
26    valueType z ;
27  } ;
28  
29  typedef struct _point3d point3d ;
30  */
31  typedef struct {
32    valueType x ;
33    valueType y ;
34    valueType z ;
35  } point3d ;
36
37  /* matrix 3 by 3 type */
38  typedef valueType matrix3d[3][3] ;
39
40  /* prototype for addition of two vectors */
41  void l3d_print( FILE * fd, point3d const * v ) ;
42
43  void l3d_scal_by_vec( valueType, point3d const * v, point3d * pRes );
44  
45  /* prototype for addition of two vectors */
46  void l3d_add( point3d const * v1, 
47                point3d const * v2,
48                point3d       * pRes ) ;
49
50  /* prototype for subtraction of two vectors */
51  void l3d_sub( point3d const * v1, 
52                point3d const * v2,
53                point3d       * pRes ) ;
54
55  /* prototype for vector product of two vectors */
56  void l3d_vec_product( point3d const * v1, 
57                        point3d const * v2,
58                        point3d       * pRes ) ;
59
60  /* prototype for dot product of two vectors */
61  valueType l3d_dot_product( point3d const * v1, 
62                             point3d const * v2 ) ;
63
64  /* initialize a matrix */
65  void l3d_zero_matrix( matrix3d m ) ;
66  void l3d_id_matrix( matrix3d m ) ;
67  void l3d_ones_matrix( matrix3d m ) ;
68  
69  void l3d_addm( matrix3d const m1, 
70                 matrix3d const m2,
71                 matrix3d       res ) ;
72
73  /* prototype for subtraction of two vectors */
74  void l3d_subm( matrix3d const m1, 
75                 matrix3d const m2,
76                 matrix3d       res ) ;
77
78  void l3d_mv( matrix3d m, 
79               point3d  const * v,
80               point3d        * pRes ) ;
81
82  void l3d_mm( matrix3d const m1, 
83               matrix3d const m2,
84               matrix3d       res ) ;
85
86#ifdef __cplusplus
87}
88#endif
89
90#endif /* close LIB3D_H */

File lib3d.c

 1/*
 2  File: lib3d.c
 3  Simple vector/matrix library for 3d vector and 3x3 matrix.
 4*/
 5
 6#include "lib3d.h"
 7
 8void
 9l3d_print( FILE * fd, point3d const * v ) {
10  fprintf( fd, "[ %lf %lf %lf]\n", v -> x, v -> y, v -> z ) ; 
11}
12
13void
14l3d_scal_by_vec( valueType s, point3d const * v, point3d * pRes ) {
15  pRes -> x = v -> x * s ;
16  pRes -> y = v -> y * s ;
17  pRes -> z = v -> z * s ;
18}
19
20
21void
22l3d_add( point3d const * v1, 
23         point3d const * v2,
24         point3d       * pRes ) {
25  /*
26  (*pRes) . x = v1 . x + v2 . x ;     
27  (*pRes) . y = v1 . y + v2 . y ;     
28  (*pRes) . z = v1 . z + v2 . z ;     
29  */
30  pRes -> x = v1 -> x + v2 -> x ;     
31  pRes -> y = v1 -> y + v2 -> y ;     
32  pRes -> z = v1 -> z + v2 -> z ;     
33}
34
35void
36l3d_sub( point3d const * v1, 
37         point3d const * v2,
38         point3d       * pRes ) {
39  pRes -> x = v1 -> x - v2 -> x ;
40  pRes -> y = v1 -> y - v2 -> y ;
41  pRes -> z = v1 -> z - v2 -> z ;
42}
43
44void
45l3d_vec_product( point3d const * v1, 
46                 point3d const * v2,
47                 point3d       * pRes ) {
48  pRes -> x = v1 -> y * v2 -> z - v1 -> z * v2 -> y ;
49  pRes -> y = v1 -> z * v2 -> x - v1 -> x * v2 -> z ;
50  pRes -> z = v1 -> x * v2 -> y - v1 -> y * v2 -> x ;
51}
52
53valueType
54l3d_dot_product( point3d const * v1, 
55                 point3d const * v2 ) {
56  return v1 -> x * v2 -> x +
57         v1 -> y * v2 -> y +
58         v1 -> z * v2 -> z ;
59}
60
61void
62l3d_zero_matrix( matrix3d m ) {
63  m[0][0] = m[0][1] = m[0][2] =
64  m[1][0] = m[1][1] = m[1][2] =
65  m[2][0] = m[2][1] = m[2][2] = 0 ;
66}
67
68void
69l3d_id_matrix( matrix3d m ) {
70  m[0][1] = m[0][2] = m[1][0] =
71  m[1][2] = m[2][0] = m[2][1] = 0 ;
72  m[0][0] = m[1][1] = m[2][2] = 1 ;
73}
74
75void
76l3d_ones_matrix( matrix3d m ) {
77  m[0][0] = m[0][1] = m[0][2] =
78  m[1][0] = m[1][1] = m[1][2] =
79  m[2][0] = m[2][1] = m[2][2] = 1 ;
80}
81
82void
83l3d_mv( matrix3d m, 
84        point3d  const * v,
85        point3d        * pRes ) {
86  valueType tmp1 = m[0][0] * v -> x + m[0][1] * v -> y + m[0][2] * v -> z ;
87  valueType tmp2 = m[1][0] * v -> x + m[1][1] * v -> y + m[1][2] * v -> z ; 
88  pRes -> z      = m[2][0] * v -> x + m[2][1] * v -> y + m[2][2] * v -> z ; 
89  pRes -> y      = tmp2 ;
90  pRes -> x      = tmp1 ;
91}

File test.c

 1#include "lib3d.h"
 2#include <stdio.h>
 3
 4int
 5main() {
 6
 7  point3d  v1, v2, v3, vbuff ;
 8  matrix3d M ;
 9
10  v1 . x  = 1 ;
11  v1 . y  = 0 ;
12  v1 . z  = 0 ;
13
14  v2 . x  = 0 ;
15  v2 . y  = 1 ;
16  v2 . z  = 0 ;
17  
18  l3d_ones_matrix( M ) ;
19
20  /* M * (v1 + 3 * v2) */
21  l3d_scal_by_vec( 3, & v2, & vbuff ); /* 3 * v2 --> vbuff */
22  l3d_add( & v1, & vbuff, & vbuff );   /* v1 + vbuff --> vbuff */
23  l3d_mv( M, & vbuff, & vbuff ) ;
24  l3d_print( stdout, & vbuff ) ;
25
26  l3d_vec_product( & v1, & v2, & v3 );
27  
28  l3d_print( stdout, & v3 ) ;
29  
30  /*printf( " v3 . x = %lf\n", v3 . x ) ;
31  printf( " v3 . y = %lf\n", v3 . y ) ;
32  printf( " v3 . z = %lf\n", v3 . z ) ;
33  */
34  return 0 ;
35}