A denoiser is a filter on a noisy estimate, not a substitute for a correct PBR material. Used well, it cuts render time on interiors with GI. Used early, it melts brushed metal, wood pores, and thin reflections into plastic. This guide is about when to click denoise and when to spend samples on the maps you already have.
What denoisers see versus what PBR stores
PBR detail lives in high-frequency roughness and normals. Monte Carlo noise also lives in high frequency, especially on glossy indirect. The denoiser cannot always tell a scratch from a firefly. Intel Open Image Denoise (OIDN) uses albedo and normal guides to protect texture. OptiX is fast on NVIDIA GPUs and can over-smooth glossy surfaces if sample count is tiny. Both assume your albedo is lighting-free. If albedo contains baked spec, the guide is a lie.
Refresh the map set in the PBR textures complete guide before you blame the denoiser for a dirty color map.
A sample budget that makes denoising safe
For stills in Cycles, a practical floor is: enough samples that the noisier of diffuse-indirect and glossy-indirect is “grain, not confetti.” Then denoise. If you can still see individual fireflies on a chrome sphere, raise samples or clamp, then denoise. Product shots of metal often need more glossy samples than a matte wood interior.
- Interiors with GI: denoise after 256–1024 samples depending on light size.
- Hero chrome or wet floor: double glossy samples; denoise lightly or only on diffuse.
- Clay or fabric: denoise earlier; roughness already hides spec noise.
Resolution of the texture is unrelated to sample count. A 4K wood does not need more samples than 2K; it needs correct filtering. See the resolution guide.
Guides, passes, and what to turn off
Enable albedo and normal passes for OIDN. Use the shader’s true albedo, not a beauty crop. Do not feed a denoiser a beauty that already has bloom and glare; denoise beauty or combined lighting, then add optical effects. In Blender, prefer denoising the combined pass or per-pass (diffuse, glossy) if metal edges smear.
Turn off denoising on alpha-thin hair and on screens that must stay sharp. Do not denoise a normal AOV you plan to use later. Light the scene with a stable HDRI so the denoiser is not chasing a moving sun in lookdev; see HDRI and PBR lighting.
Animation versus stills
Per-frame OptiX on a camera move will crawl on tiled floors. That crawl is the filter locking onto different noise each frame. Fixes: temporal denoising (engine or comp), more samples, or a slightly higher roughness on huge tiled floors so the highlight is less like a laser. Do not animate denoiser strength.
For stills destined for print, compare a cropped 100% of wood pores with and without denoise. If pores vanish, you filtered the material. Keep the noisier version or raise samples.
Practical workflow with CC0 maps
- Lookdev materials under IBL without denoise so you see true roughness.
- Lock maps from the Locker3d catalog (free CC0; you may blur a roughness copy if a scan is too noisy). License: CC0 can and cannot.
- Enable denoise only for final stills or for viewport iteration, not for both with different settings you forget to match.
- If the denoiser invents “watercolor” blotches on walls, albedo is too noisy or too dark; fix the texture, not the filter.
More render-process notes are on the blog. Denoising should shorten a correct render, not hide an under-sampled or mis-authored PBR stack.
Frequently asked questions
Should I denoise every PBR still?
Denoise when noise is in indirect lighting or high-frequency spec, and you are already at a reasonable sample count. Do not denoise a 16-sample hero product shot and expect brushed metal to survive. Raise samples first on metals and glass.
Why does denoising smear my normal-map detail?
Denoisers average neighborhoods. Fine normal and roughness variation looks like noise. Use albedo/normal/roughness AOVs as guides (OIDN) or keep a higher sample cap on glossy passes. Lowering normal intensity to “help the denoiser” destroys the material.
Is GPU denoising safe for animation?
Per-frame denoisers flicker on moving highlights. Use temporal denoising or a higher sample count for animation. Still frames can use OptiX or OIDN more aggressively.