Updated readme.md

README.md

@@ -1 +1,22 @@
 # cuda-based-raytrace
+
+## How to run
+If necessary clean previous build:
+```bash
+make clean
+```
+
+Then build (currently always debug build):
+```bash
+make all
+```
+
+Run:
+```bash
+./build/main
+```
+
+To open the resulting image you can use (Ubuntu):
+```bash
+xdg-open output.ppm
+```