In [_Ray Tracing in One Weekend_](/works/OL43888192W), you built a simple brute force path tracer. In this installment we’ll add textures, volumes (like fog), rectangles, instances, lights, and support for lots of objects using a BVH. When done, you’ll have a “real” ray tracer. A heuristic in ray tracing that many people—including me—believe, is that most optimizations complicate the code without delivering much speedup. What I will do in this mini-book is go with the simplest approach in each design decision I make. See our Further Reading wiki page for additional project related resources. However, I strongly encourage you to do no premature optimization; if it doesn’t show up high in the execution time profile, it doesn’t need optimization until all the features are supported! The two hardest parts of this book are the BVH and the Perlin textures. This is why the title suggests you take a week rather than a weekend for this endeavor. But you can save those for last if you want a weekend project. Order is not very important for the concepts presented in this book, and without BVH and Perlin texture you will still get a Cornell Box!