Revise README for project details and benchmarks

Updated project description and added performance benchmarks.

README.md

@@ -1,2 +1,30 @@
-# multithreaded-raytracer
-A CPU-based ray tracer written and implemented following Peter Shirley’s Ray Tracing in One Weekend series, but extended with multithreaded rendering.
+# Multithreaded Ray Tracer
+
+## Ray Tracing in One Weekend
+
+This project is an implementation of Peter Shirley’s  
+[*Ray Tracing in One Weekend*](https://raytracing.github.io/books/RayTracingInOneWeekend.html),  
+the first book in the Ray Tracing trilogy series, written in C++.
+
+In addition to single threaded implementation, I've added multithreading to keep the render time reasonable.
+
+---
+
+### Final Render (500 Samples Per Pixel, 1200×675)
+
+![Final Render](final_Renders/final_render.png)
+
+---
+
+## Performance Benchmark
+
+My CPU is Intel Core i9-13900H with 8E and 6P cores (20 logical threads). The above image was rendered in about 5m 20s with all of the logical threads saturated and CPU utilization at ~95% with a base clock of 2.8GHz. The image consists of 500 samples per pixel, 50 Max recursion depth at 1200 x 675 resolution. The original PPM image was converted to PNG format using ImageMagick.
+
+
+### Render Time
+
+| Mode              | Render Time |
+|-------------------|------------|
+| Single-threaded   | 2 hours 59 minutes |
+| Multithreaded     | 5 minutes 20 seconds |
+