🚀 Building a Ray Tracer in C++: Reflection, Shading, and Optimization
Ray tracing is a powerful rendering technique that simulates how light interacts with objects to produce photorealistic images. In this post, we explain how we built a ray tracer from scratch in C++, including core components like intersection detection, shading, and recursive reflection.
🔍 Overview Our C++ ray tracer supports:
Triangle mesh rendering
Flat and reflective shaders
Texture mapping
Recursive reflections
Background shading
Performance optimizations
We designed the system to be modular, extensible, and relatively efficient.
🎯 1. Ray Generation The process begins by casting a ray from the camera through the center of each pixel on the screen.
For each pixel:
Compute the world-space position of the pixel
Subtract the camera origin to get the ray direction
Normalize the direction and create a Ray
The ray is passed to the main function Cast_Ray, which determines what color should be shown at that pixel.
📌 2. Finding Intersections We call Closest_Intersection(ray) to find which object in the scene the ray hits first.
This function:
Iterates through all objects in the scene
Calls each object’s Intersection() method
Tracks the closest hit where hit.dist >= small_t
If no intersection is found, we fall back to a background_shader if defined.
🎨 3. Shading Logic Once we know the intersection point and surface normal, we compute the color using the associated shader.
Our ray tracer supports different shaders:
Flat Shader – simple lighting based on a normal and a single light
Background Shader – used when no object is hit
Reflective Shader – blends reflection with another shader
Each shader implements a Shade_Surface() function, which returns an RGB color.
🔁 4. Reflections (Recursive Rays) The Reflective_Shader computes a reflection direction based on the incoming ray and surface normal:
Uses the formula reflected = v - 2 * dot(v, normal) * normal
Creates a new reflected ray with a small offset to avoid self-intersection
Calls Cast_Ray again with recursion_depth - 1
The result is a mix of the base color and the reflected color, controlled by a reflectivity factor (clamped between 0 and 1).
🛠️ 5. Optimizations To improve performance and avoid rendering artifacts, we implemented several optimizations:
Early Exit: Rays with recursion_depth <= 0 return black immediately
Offset Rays: A small position offset (+ normal * 0.001) prevents self-shadowing
Modular Shading: Reflective shaders can wrap any other shader
Clean Memory Management: Proper deletion of all objects, shaders, and lights
Further optimizations we plan to explore:
Spatial acceleration (e.g., BVH or uniform grids)
Multi-threaded rendering
Anti-aliasing with supersampling
🧪 Visual Results With this setup, the ray tracer can render complex scenes with textured triangle meshes (like a 3D cow), spheres, reflections, shadows, and realistic lighting. The final images are rendered one pixel at a time, simulating light physics.
🧵 Conclusion Building a ray tracer from scratch in C++ was both a technically demanding and creatively rewarding experience. It strengthened our understanding of:
Geometry and linear algebra
Lighting models
Memory and performance optimization
Software modularity and extensibility
This project serves as a strong foundation for future work in computer graphics, game engines, and physically based rendering.