--- ray/src/gen/mkillum.c	1991/08/13 14:43:49	1.11
+++ ray/src/gen/mkillum.c	1991/11/08 13:17:44	1.14
@@ -42,6 +42,7 @@ struct illum_args  thisillum = {	/* our illum and defa
 		VOIDID,
 		SAMPDENS,
 		NSAMPS,
+		0.,
 	};
 
 char	matcheck[MAXSTR];	/* current material to include or exclude */
@@ -146,6 +147,7 @@ init()				/* start rtrace and set up buffers */
 					/* set up signal handling */
 	signal(SIGPIPE, quit);
 					/* start rtrace process */
+	errno = 0;
 	maxbytes = open_process(rt.pd, rtargv);
 	if (maxbytes == 0) {
 		eputs(rtargv[0]);
@@ -329,6 +331,16 @@ char	*nm;
 				break;
 			cp++;
 			continue;
+		case 'b':			/* brightness */
+			if (*++cp != '=')
+				break;
+			if (!isfltd(++cp, " \t\n"))
+				break;
+			thisillum.minbrt = atof(cp);
+			if (thisillum.minbrt < 0.)
+				thisillum.minbrt = 0.;
+			cp = sskip(cp);
+			continue;
 		case 'o':			/* output file */
 			if (*++cp != '=')
 				break;
@@ -376,6 +388,7 @@ printopts()			/* print out option default values */
 	printf("c=n\t\t\t\t# color none\n");
 	printf("d=%d\t\t\t\t# density of points\n", thisillum.sampdens);
 	printf("s=%d\t\t\t\t# samples per point\n", thisillum.nsamps);
+	printf("b=%f\t\t\t# minimum average brightness\n", thisillum.minbrt);
 }