Nvidia offers ray tracing like software filters for non-RT games

In a fast-paced game, players won’t be able to tell the difference.

In their January 2022 driver update, Nvidia added an option to allow end users to add ray tracing-like quality to their games through the Nvidia game filters option and Screen Space Ray Traced Global Illumination (SSRTGI). SSRTGI, screen-space ambient occlusion, and dynamic depth of field filters allow users to make games look more cinematic and photorealistic.

Nvidia used Pascal Gilcher’s (aka Marty McFly) popular ReShade software to add the filters into Nvidia’s GeForce Experience application launcher for the PC. The ray tracing Reshade filter had been one of Gilcher’s most popular releases, and Nvidia made it accessible to its gaming community. Users can add ray tracing-like quality to supported titles without waiting for the game developer to add it.

SSRTGI isn’t the same as traditional ray tracing, which looks for intersections in the triangles. SSRTGI renders in the pixel buffer and uses a ray marching technique. It still gives a realistic look by evaluating the distance from the light source and looking (for) objects that are a barrier to light.

Ray marching takes a different approach to the ray–object intersection problem. Ray marching does not calculate an intersection analytically. Instead, it marches a point along the ray until it finds a point that intersects an object.

Most ray tracing experts define triangle-based intersection as ray tracing. Therefore, if the image enhancement is done in the pixel shader stage, it is not ray tracing. So by that definition, ray marching is not a ray tracing solution. It is an approximation resulting in false lighting, just as scan-line or raster imaging is false lighting. The word false should not be seen as a criticism; it is merely a definition or a differentiation.

In addition to the ray marching process, Nvidia added other depth-based filters to GeForce Experience Freestyle.

SSAO (Screen Space Ambient Occlusion) emphasizes the appearance of shadows near the intersections of 3D objects, especially within dimly lit/indoor environments.

Dynamic DOF (Depth of Field) applies bokeh-style blur based on the proximity of objects within the scene, giving a game a more cinematic look and feel.

What do we think?

Since the SSRTGI is ray marching and RM does its work in the pixel shader, SSRTGI does not use any RTX RT engines. Theoretically, SSRTGI could work on any GPU. Therefore, we can probably expect to see an AMD version soon.