--- ray/src/common/mat4.c	1989/02/02 10:34:35	1.1
+++ ray/src/common/mat4.c	1991/11/12 16:54:53	2.1
@@ -1,4 +1,4 @@
-/* Copyright (c) 1986 Regents of the University of California */
+/* Copyright (c) 1990 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -10,28 +10,16 @@ static char SCCSid[] = "$SunId$ LBL";
  *     10/19/85
  */
 
+#include  "mat4.h"
 
-static double  m4tmp[4][4];		/* for efficiency */
+MAT4  m4ident = MAT4IDENT;
 
-#define  copymat4(m4a,m4b)	bcopy((char *)m4b,(char *)m4a,sizeof(m4tmp))
+static MAT4  m4tmp;		/* for efficiency */
 
 
-setident4(m4)
-double  m4[4][4];
-{
-	static double  ident[4][4] = {
-		1.,0.,0.,0.,
-		0.,1.,0.,0.,
-		0.,0.,1.,0.,
-		0.,0.,0.,1.,
-	};
-	copymat4(m4, ident);
-}
-
-
 multmat4(m4a, m4b, m4c)		/* multiply m4b X m4c and put into m4a */
-double  m4a[4][4];
-register double  m4b[4][4], m4c[4][4];
+MAT4  m4a;
+register MAT4  m4b, m4c;
 {
 	register int  i, j;
 	
@@ -47,17 +35,14 @@ register double  m4b[4][4], m4c[4][4];
 
 
 multv3(v3a, v3b, m4)	/* transform vector v3b by m4 and put into v3a */
-double  v3a[3];
-register double  v3b[3];
-register double  m4[4][4];
+FVECT  v3a;
+register FVECT  v3b;
+register MAT4  m4;
 {
-	register int  i;
+	m4tmp[0][0] = v3b[0]*m4[0][0] + v3b[1]*m4[1][0] + v3b[2]*m4[2][0];
+	m4tmp[0][1] = v3b[0]*m4[0][1] + v3b[1]*m4[1][1] + v3b[2]*m4[2][1];
+	m4tmp[0][2] = v3b[0]*m4[0][2] + v3b[1]*m4[1][2] + v3b[2]*m4[2][2];
 	
-	for (i = 0; i < 3; i++)
-		m4tmp[0][i] = v3b[0]*m4[0][i] +
-			      v3b[1]*m4[1][i] +
-			      v3b[2]*m4[2][i];
-	
 	v3a[0] = m4tmp[0][0];
 	v3a[1] = m4tmp[0][1];
 	v3a[2] = m4tmp[0][2];
@@ -65,9 +50,9 @@ register double  m4[4][4];
 
 
 multp3(p3a, p3b, m4)		/* transform p3b by m4 and put into p3a */
-register double  p3a[3];
-double  p3b[3];
-register double  m4[4][4];
+register FVECT  p3a;
+FVECT  p3b;
+register MAT4  m4;
 {
 	multv3(p3a, p3b, m4);	/* transform as vector */
 	p3a[0] += m4[3][0];	/* translate */
@@ -76,38 +61,39 @@ register double  m4[4][4];
 }
 
 
-#ifdef  INVMAT
 /*
  * invmat - computes the inverse of mat into inverse.  Returns 1
- * if there exists an inverse, 0 otherwise.  It uses Gause Elimination
- * method.
+ * if there exists an inverse, 0 otherwise.  It uses Gaussian Elimination
+ * method with partial pivoting.
  */
 
 invmat(inverse,mat)
-double mat[4][4],inverse[4][4];
+MAT4  mat, inverse;
 {
 #define SWAP(a,b,t) (t=a,a=b,b=t)
+#define ABS(x) (x>=0?x:-(x))
 
 	register int i,j,k;
 	register double temp;
 
-	setident4(inverse);
 	copymat4(m4tmp, mat);
+	setident4(inverse);
 
 	for(i = 0; i < 4; i++) {
-		if(m4tmp[i][i] == 0) {    /* Pivot is zero */
-			/* Look for a raw with pivot != 0 and swap raws */
-			for(j = i + 1; j < 4; j++)
-				if(m4tmp[j][i] != 0) {
-					for( k = 0; k < 4; k++) {
-						SWAP(m4tmp[i][k],m4tmp[j][k],temp);
-						SWAP(inverse[i][k],inverse[j][k],temp);
-						}
-					break;
-					}
-			if(j == 4)	/* No replacing raw -> no inverse */
-				return(0);
-			}
+		/* Look for row with largest pivot and swap rows */
+		temp = 0; j = -1;
+		for(k = i; k < 4; k++)
+			if(ABS(m4tmp[k][i]) > temp) {
+				temp = ABS(m4tmp[k][i]);
+				j = k;
+				}
+		if(j == -1)	/* No replacing row -> no inverse */
+			return(0);
+		if (j != i)
+			for(k = 0; k < 4; k++) {
+				SWAP(m4tmp[i][k],m4tmp[j][k],temp);
+				SWAP(inverse[i][k],inverse[j][k],temp);
+				}
 
 		temp = m4tmp[i][i];
 		for(k = 0; k < 4; k++) {
@@ -125,5 +111,7 @@ double mat[4][4],inverse[4][4];
 			}
 		}
 	return(1);
+
+#undef ABS
+#undef SWAP
 }
-#endif