Free camera movement. Somewhat.

I don't know, goniometry is hard.

src/utils.hpp

@@ -2,6 +2,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <cmath>
 #include <fstream>
 #include <iterator>
 #include <string>
@@ -121,4 +122,9 @@ namespace fmri
         }
     }
 
+    template<class T>
+    constexpr inline T deg2rad(T val) {
+        return val / 180 * M_PI;
+    }
+
 }