Here is a list of compile switches, used to customize Radiance code
for specific machines and users:

-DMC		If set, switches from default low-discrepency sequence
		sampling to true (pseudorandom) Monte Carlo.  Use if
		the "brushed" appearance of specular highlights and
		penumbras bothers you.

-DALIGN=(type)	Alignment type, machine-dependent.  Most RISC
		architectures align on 8-word boundaries (double).
		The default alignment type is int.

-DSPEED=(MIPS)	Millions of instructions per second for this
		processor (approximate).  This is used to decide
		certain unimportant timing issues such as how many
		rays to trace before checking input in rview and
		whether or not to optimize the color table in ximage
		on 8-bit displays.

-DWFLUSH=(rays)	Override for number of rays before flush in rview.

-DBSD		Operating system has a strong Berkeley flavor, meaning
		that bcopy() and bzero() are present but maybe memcpy()
		and memset() are not.  (See common/standard.h for other
		things this flag affects.)  Also affects certain system
		calls, such as signal handling and resource tracking.

-DBIGMEM	The system has lots of RAM available, so size hash
		tables and the like accordingly.  Also provides for
		larger overall scene descriptions (33,553,920 primitives
		rather than 32,256).

-DSMLFLT	This setting tells Radiance to use short floats
		(4-bytes) throughout, which saves lots of memory
		but can cause calculation inaccuracies in many
		cases.  Its use has been discontinued for this reason.