RTX Texture Filtering in Reference Path Tracing

The StandardLit reference path tracer integrates NVIDIA RTX Texture Filtering (RTXTF) from Shaders/ThirdParty/RTXTF. The vendored source is taken from the RTXTF library supplied in E:\RTXTF\libraries\RTXTF-Library; its NVIDIA license is retained beside the shader headers.

Scope

• RTXTF is enabled by default for opaque StandardLit surface texture reads in ReferencedPathtracingDXR.
• Alpha-tested, transparent, and virtual-textured materials retain their visibility-safe sampling path. RTXTF's upstream documentation identifies alpha maps and off-screen visibility buffers as problematic stochastic uses.
• Ray-cone LOD selection remains owned by the reference path tracer. RTXTF stochastically selects the texel and fractional mip sample at that explicit LOD.
• Collaborative magnification is disabled in closest-hit shaders because a ray wave does not guarantee coherent screen-space lanes.

Settings

Use the VividRP/Path Tracing/Reference Path Tracing volume component:

• Enable RTXTF toggles stochastic texture filtering.
• RTXTF Filter selects Linear, Cubic, or Gaussian reconstruction.
• RTXTF Gaussian Sigma controls the Gaussian footprint in texels.

Linear converges to the existing hardware-filtered result and is the default. Cubic and Gaussian create a noisier per-frame signal and need temporal accumulation or ray reconstruction to resolve. Changing any RTXTF setting is part of the integrator signature and therefore invalidates old accumulation.