Add viewTransform transformation

source/include/transformation.h

@@ -21,4 +21,6 @@ Matrix rotationZ(double angle);
 
 Matrix shearing(double Xy, double Xx, double Yx, double Yz, double Zx, double Zy);
 
+Matrix viewTransform(Tuple from, Tuple to, Tuple up);
+
 #endif /* DORAYME_TRANSFORMATION_H */

source/transformation.cpp

@@ -81,4 +81,19 @@ Matrix shearing(double Xy, double Xz, double Yx, double Yz, double Zx, double Zy
     ret.set(2, 1, Zy);
 
     return ret;
+}
+
+Matrix viewTransform(Tuple from, Tuple to, Tuple up)
+{
+    Tuple forward = (to - from).normalise();
+    Tuple left = forward.cross(up.normalise());
+    Tuple true_up = left.cross(forward);
+
+    double orientationValues[] = {  left.x,     left.y,     left.z,    0,
+                                    true_up.x,  true_up.y,  true_up.z, 0,
+                                   -forward.x, -forward.y, -forward.z, 0,
+                                    0,          0,          0,         1 };
+    Matrix orientation = Matrix4(orientationValues);
+
+    return orientation * translation(-from.x, -from.y, -from.z);
 }