tracing in 3D optical systems with a finite set of reflective or partially reflective objects represented by a system of rational linear inequalities is PSPACE-hard. For any dimension equal to or greater than 2, ray tracing with a finite set of parallel and perpendicular reflective surfaces represented by rational linear inequalities is in PSPACE. See also Beam tracing Cone tracing Distributed ray tracing Global illumination Gouraud shading List of ray tracing software Parallel computing Path tracing Phong shading Progressive refinement Shading Specular reflection Tessellation Per-pixel lighting GPUOpen Nvidia GameWorks Metal (API) Vulkan DirectX References External links Interactive Ray Tracing: The replacement of rasterization? The Compleat Angler (1978) Writing a Simple Ray Tracer (scratchapixel) Ray tracing a torus Ray Tracing in One Weekend Book Series Webarchive template wayback links Geometrical optics Virtual reality Global illumination algorithms Computer graphics 3D computer graphics Shading