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root/Development/ray/src/common/mat4.c

Comparing ray/src/common/mat4.c (file contents):
Revision 2.1 by greg, Tue Nov 12 16:54:53 1991 UTC vs.
Revision 2.2 by greg, Thu Jun 23 10:22:20 1994 UTC

#	Line 59 | Line 59 | register MAT4  m4;
59		p3a[1] += m4[3][1];
60		p3a[2] += m4[3][2];
61		}
62	–
63	–
64	–	/*
65	–	* invmat - computes the inverse of mat into inverse.  Returns 1
66	–	* if there exists an inverse, 0 otherwise.  It uses Gaussian Elimination
67	–	* method with partial pivoting.
68	–	*/
69	–
70	–	invmat(inverse,mat)
71	–	MAT4  mat, inverse;
72	–	{
73	–	#define SWAP(a,b,t) (t=a,a=b,b=t)
74	–	#define ABS(x) (x>=0?x:-(x))
75	–
76	–	register int i,j,k;
77	–	register double temp;
78	–
79	–	copymat4(m4tmp, mat);
80	–	setident4(inverse);
81	–
82	–	for(i = 0; i < 4; i++) {
83	–	/* Look for row with largest pivot and swap rows */
84	–	temp = 0; j = -1;
85	–	for(k = i; k < 4; k++)
86	–	if(ABS(m4tmp[k][i]) > temp) {
87	–	temp = ABS(m4tmp[k][i]);
88	–	j = k;
89	–	}
90	–	if(j == -1)     /* No replacing row -> no inverse */
91	–	return(0);
92	–	if (j != i)
93	–	for(k = 0; k < 4; k++) {
94	–	SWAP(m4tmp[i][k],m4tmp[j][k],temp);
95	–	SWAP(inverse[i][k],inverse[j][k],temp);
96	–	}
97	–
98	–	temp = m4tmp[i][i];
99	–	for(k = 0; k < 4; k++) {
100	–	m4tmp[i][k] /= temp;
101	–	inverse[i][k] /= temp;
102	–	}
103	–	for(j = 0; j < 4; j++) {
104	–	if(j != i) {
105	–	temp = m4tmp[j][i];
106	–	for(k = 0; k < 4; k++) {
107	–	m4tmp[j][k] -= m4tmp[i][k]*temp;
108	–	inverse[j][k] -= inverse[i][k]*temp;
109	–	}
110	–	}
111	–	}
112	–	}
113	–	return(1);
114	–
115	–	#undef ABS
116	–	#undef SWAP
117	–	}

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