Improve Makefile to support build shared library and update the documentation

Author: sdhzhs

Makefile

@@ -2,13 +2,17 @@ vpath %.o obj
 
 # compile macro
 CC = gcc
-CCFLAGS = -W -O3
+CCFLAGS = -W -O3 -fPIC
 LDFLAGS = -O3 -lm
 INCLUDES = -I.
 
 src:=$(sort $(wildcard *.c))
-objects:=$(src:.c=.o)
+mainsrc:=main.c
+libsrc:=$(filter-out $(mainsrc),$(src))
+libobjects:=$(libsrc:.c=.o)
+mainobject:=$(mainsrc:.c=.o)
 exec:=polyop
+libname:=libpolyboolean.so
 bprefix:=bin/
 oprefix:=obj/
 bdir:=bin
@@ -20,14 +24,21 @@ cp:=cp -f
 cd:=cp -r -f
 
 vpath $(exec) bin
+vpath $(libname) bin
 
 # dependence
 %.o: %.c|$(odir)
 	${CC} ${CCFLAGS} ${INCLUDES} -c $< -o $(addprefix $(oprefix),$@)
-$(exec):$(objects)|$(bdir)
-	$(CC) $(addprefix $(oprefix),$(objects)) $(LDFLAGS) -o $(addprefix $(bprefix),$(exec))
+
+$(exec): $(mainobject) $(libname)|$(bdir)
+	$(CC) $(addprefix $(oprefix),$(mainobject)) -L$(bdir) -lpolyboolean -Wl,-rpath,'$$ORIGIN' $(LDFLAGS) -o $(addprefix $(bprefix),$(exec))
+
+$(libname): $(libobjects)|$(bdir)
+	$(CC) -shared $(addprefix $(oprefix),$(libobjects)) $(LDFLAGS) -o $(addprefix $(bprefix),$(libname))
+
 $(odir):
 	-$(md) $(odir)
+
 $(bdir):
 	-$(md) $(bdir)
 

README.md

@@ -5,7 +5,7 @@ The C codes in this repository are extracted and extended from one Computer Aide
 
 Data structure
 
-The data structure for polygons is just array in double precision floating number which represents ordered points set in 3D space.  The order of points set in the first (poly1) and second (poly2) polygon should be identical (both clockwise or both counterclockwise).  Obviously the polygons should be planar (or approximately planar based on geometric tolerance) for valid Boolean operations.  The reason why the polygons are 3D is the application scenarios in CAE is always three dimensional and some approximate cases should be treated.  Because the focus of functions in the codes is on Boolean operations of two polygons, no extra tree-like data structure is introduced to improve the efficiency of geometric calculation, which is commonly used in Boolean operations of polygons (graphs) in large amount.  The application in CAE shows the codes are efficient if the number of points and Boolean operations are not larger than 1M.
+The data structure for polygons is just array in double precision floating number which represents ordered points set in 3D space.  The order of points set in the first (poly1) and second (poly2) polygon should be identical (both clockwise or both counterclockwise if viewing along a certain direction).  Obviously the polygons should be planar (or approximately planar based on geometric tolerance) for valid Boolean operations.  The reason why the polygons are 3D is that the application scenarios in CAE is always three dimensional and some approximate cases should be treated.  Because the focus of functions in the codes is on Boolean operations of two polygons, no extra tree-like data structure is introduced to improve the efficiency of geometric calculation, which is commonly used in Boolean operations of polygons (graphs) in large amount.  The application in CAE shows the codes are efficient if the number of points and Boolean operations are not larger than 1M.
 
 Algorithm