--- ray/src/rt/renderopts.c	2024/04/05 17:52:20	2.25
+++ ray/src/rt/renderopts.c	2025/04/22 17:12:25	2.27
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: renderopts.c,v 2.25 2024/04/05 17:52:20 greg Exp $";
+static const char	RCSid[] = "$Id: renderopts.c,v 2.27 2025/04/22 17:12:25 greg Exp $";
 #endif
 /*
  *  renderopts.c - process common rendering options
@@ -10,6 +10,7 @@ static const char	RCSid[] = "$Id: renderopts.c,v 2.25 
 #include "copyright.h"
 
 #include  "ray.h"
+#include  "func.h"
 #include  "paths.h"
 #include  "pmapopt.h"
 
@@ -75,7 +76,8 @@ match_subfeatures(	/* check if subfeatures are support
 		while (*reqs && (*cp = *reqs++) != ',')
 			cp++;
 		*cp = '\0';
-		n = cp - subfeat;
+		if (!(n = cp - subfeat))
+			continue;	/* empty subfeature */
 		for (cp = mysublist; (cp = strstr(cp, subfeat)) != NULL; cp++)
 			if ((cp[-1] == ',') | (cp[-1] == '=') &&
 					(cp[n] == ',') | (cp[n] == '\n'))
@@ -312,6 +314,20 @@ getrenderopt(		/* get next render option */
 			return(1);
 		}
 		break;
+	case 'f':				/* .cal file */
+		if (av[0][2])
+			break;
+		check(2,"s");
+		loadfunc(av[1]);
+		return(1);
+	case 'e':				/* .cal expression */
+		if (av[0][2])
+			break;
+		check(2,"s");
+		if (!strchr(av[1], '=') && !strchr(av[1], ':'))
+			break;
+		scompile(av[1], NULL, 0);
+		return(1);
 #if MAXCSAMP>3
 	case 'c':				/* spectral sampling */
 		switch (av[0][2]) {