Updated README file

README.md

@@ -1,2 +1,12 @@
 # Raytracing
 This is a Raytracing made from scratch in C++, using a C++ wrapper of Allegro I did.
+
+
+# How to build :
+Compile using : -std=c++11 -lpthread;allegro;allegro_image;allegro_primitives;allegro_memfile;allegro_ttf;allegro_font
+-Wl,--format=binary -Wl,arial.ttf -Wl,--format=default
+
+The last line is required to include the arial.ttf file __inside__ the executable, at link time. This avoids having to share your program and the font file as two separate files.
+
+The optimisation level -O2 is highly recommended as it's 5 times as performant as lesser ones. Also -O3 and higher causes weird shadows glitches I didn't identify yet.
+