ReShade emerged as a generic post-processing injector that allows custom shaders to be applied to any DirectX 9–12 or OpenGL game. Among the most popular custom shader packs are those implementing screen-space ray tracing (SSRT). These shaders approximate ray-traced effects using only the color and depth buffers of the current frame.
float trace_ray(float3 ray_origin, float3 ray_dir, float max_steps, float step_size) float2 uv = ray_origin.xy; float depth = ray_origin.z; for (int i = 0; i < max_steps; i++) uv += ray_dir.xy * step_size; float sampled_depth = tex2D(depthBuffer, uv).r; float ray_depth = ray_origin.z + (i * step_size * ray_dir.z); if (ray_depth >= sampled_depth + epsilon) return sampled_depth; return INF; reshade ray tracing
Author: [Generated for academic purposes] Affiliation: Computer Graphics & Interactive Techniques Laboratory Date: April 14, 2026 Abstract Real-time ray tracing has traditionally been confined to modern graphics APIs (DirectX 12 Ultimate, Vulkan RT) and dedicated hardware (NVIDIA RTX, AMD RDNA 2+). However, a growing community of modders and developers has demonstrated that approximate ray tracing effects can be injected into older or unmodified games using screen-space data. This paper examines ReShade , a generic post-processing injector, and its suite of ray tracing shaders (e.g., qUINT RT , Martys Mods Ray Tracing , RTGI ). We analyze the underlying algorithms—primarily screen-space ray marching, Monte Carlo denoising, and temporal accumulation—and evaluate their performance, visual quality, and limitations compared to native hardware-accelerated ray tracing. Our findings show that while ReShade ray tracing suffers from occlusion artifacts and lacks scene geometry beyond the camera view, it provides a surprisingly effective approximation of global illumination, ambient occlusion, and reflections, especially in static or semi-static scenes. 1. Introduction The introduction of hardware-accelerated ray tracing has revolutionized real-time graphics, offering physically accurate lighting, shadows, and reflections. However, adoption remains limited to titles built on DirectX 12 Ultimate or Vulkan RT, leaving a vast library of older games (DirectX 9–11, OpenGL) without native ray tracing support. ReShade emerged as a generic post-processing injector that