Ray Tracing
A rendering technique that traces the path of light rays from the camera through each pixel, simulating reflection, refraction, and shadows with physical accuracy to produce photorealistic images.
Ray tracing traces light rays backward from a virtual camera through each pixel, computing color at intersection points. Since Turner Whitted's 1980 paper on recursive ray tracing, it has been the foundation of photorealistic rendering in film VFX and visualization.
- Primary rays: Cast from camera through each pixel to find the nearest surface intersection, the starting point for lighting calculations
- Shadow rays: Cast from intersections toward light sources. Occluding objects indicate shadow. Soft shadows use multiple rays toward area light samples
- Reflection/refraction: Mirror surfaces trace reflection direction; transparent materials follow Snell's law. Recursion depth controls quality vs. cost
- Path tracing: Monte Carlo sampling traces random directions for physically accurate global illumination. Requires denoisers (Intel OIDN, OptiX) for clean output
NVIDIA RTX GPUs (2018+) with dedicated RT cores enabled real-time ray tracing. Through DXR and Vulkan Ray Tracing, games implement hybrid rendering - rasterization for primary visibility plus ray tracing for reflections, shadows, and GI. Full path tracing remains expensive, making DLSS/FSR upscaling essential companions.