--- ray/src/gen/mkillum.c	1991/08/23 12:30:29	1.12
+++ ray/src/gen/mkillum.c	1991/11/08 13:17:44	1.14
@@ -147,6 +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]);
@@ -336,6 +337,8 @@ char	*nm;
 			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 */