3ds Max: Reduce Arnold Noise Without Long Render Times

Arnold noise arises because too few rays per pixel are traced.

Arnold is a path tracer: it shoots a number of random rays into the scene per pixel to calculate light. If there are too few, the result differs per pixel, and you see noise – the grainy specks in shadows, reflections, and indirect light. More rays give a cleaner image but a longer render time. The goal is not simply more samples, but to distribute samples intelligently and remove any remaining noise with a denoiser.

You set this up via Render Setup (shortcut F10), Arnold Renderer tab, rollout Sampling and Ray Depth. That’s where the controls are that govern the quantity and distribution of rays. Before you crank up samples everywhere, it’s worth knowing what type of noise you’re fighting, because each type has its own setting.

Noise appears in different forms, each with a different cause:

• Overall grain across the entire image: Camera (AA) too low.
• Noise in soft shadows: too few light samples on an area light.
• Noise in reflections: too few specular samples.
• Noise in indirect light on matte surfaces: too few diffuse samples.
• Scattered bright spots (fireflies): no clamping.

Recognise the type, and you’ll know instantly which control to adjust, avoiding doubling the render time by raising the wrong setting.

Camera (AA) samples is the main control that multiplies all other samples.

The Camera (AA) samples determine how many rays per pixel the camera fires. The number of rays per pixel is the square of this value: at Camera (AA) 5, that’s 25 rays. Importantly, this value acts as a multiplier for all other samples, including light samples. If you increase Camera (AA), total render time rises quickly, but almost all types of noise disappear at once.

Practical guidelines for production work:

• Camera (AA) between 3 and 6 for most scenes.
• Higher values (6 to 10) only for stubborn noise in complex lighting.
• First lower Camera (AA) and raise specific samples (diffuse, specular) if only one type of noise remains; that’s more efficient than increasing everything.

Because Camera (AA) multiplies everything, it’s the most expensive control. Use it to eliminate general noise, and the individual sample settings to target a specific problem.

Do the maths to understand the impact. A diffuse sample of 2 means 2 squared, so 4 rays, but these are further multiplied by the Camera (AA) squared. With Camera (AA) 4 and diffuse 2, that’s 16 × 4 = 64 diffuse rays per pixel. If you double Camera (AA) to 8, the total load quadruples. That’s why it almost always pays to raise the cheaper, targeted samples first and only then adjust Camera (AA).

Adaptive sampling sends extra rays only to the noisy parts of the image.

With Adaptive Sampling, Arnold analyses during rendering where the image is still noisy and spends extra rays there, while smooth areas can manage with fewer rays. This saves render time because you’re not computing the entire image at the highest level.

Set up adaptive sampling like this:

1. Tick Enable under Adaptive Sampling in the Sampling and Ray Depth rollout.
2. Set Max. Camera (AA) higher than the regular Camera (AA), for example 8 to 20. This is the ceiling Arnold may use in noisy regions.
3. Lower the Adaptive Threshold (noise threshold) for a cleaner render; a lower value (e.g. 0.01 or 0.005) makes Arnold work longer until noise falls below that threshold.

Render Setup (F10) > Arnold Renderer > Sampling and Ray Depth > Adaptive Sampling: Enable
Camera (AA) = 4, Max. Camera (AA) = 12, Adaptive Threshold = 0.01

Adaptive sampling only works if Max. Camera (AA) is larger than the regular Camera (AA), and the Camera (AA) itself is greater than 1. If the threshold is too high, Arnold stops too early and noise remains; too low makes the render unnecessarily long.

Ray Depth determines how many times a ray bounces and how realistic, but also how noisy, the light becomes.

The Ray Depth settings control the number of bounces per ray type: Diffuse, Specular, Transmission and Volume, with an overarching Total limit. More bounces give more realistic indirect light and translucent materials, but cost time and can add noise.

Don’t set the depth higher than needed. Each extra bounce adds calculation that can reintroduce noise. For most scenes, a diffuse depth of 2 or 3 and a specular depth of 2 are sufficient; only glass and liquid scenes ask for a higher transmission depth.

Clamping suppresses fireflies, the bright white noise spots in the image.

Fireflies are isolated, extremely bright pixels caused by a single ray that catches a lot of light, for instance from a tiny, intense highlight. More samples barely eliminate them. The solution is clamping: you cap the maximum brightness a sample may contribute.

• Tick Clamp AA Samples in the sampling rollout.
• Set a Clamp Value (e.g. between 3 and 10). A lower value removes more fireflies but also dulls bright highlights.
• Tick Affect AA Samples so the clamp works on the anti-aliasing samples.

Don’t set the clamp value too low, or you’ll lose legitimate bright accents such as sun reflections. Start around 10 and lower step by step until the fireflies are gone without the image becoming flat.

Increase targeted samples when noise persists in shadows or specific materials.

If, after the general settings, a specific type of noise remains, tackle the source rather than raising Camera (AA) everywhere:

• Noisy soft shadows: increase the Samples of the relevant area light (in the light properties). More light samples smooth out soft shadow edges.
• Noisy reflections: increase the Specular samples in the sampling rollout.
• Noisy indirect light on matte surfaces: increase the Diffuse samples.
• Noisy translucency or SSS: increase the Transmission or SSS samples.

To see which type of noise you have, render separate AOVs (render elements) such as diffuse, specular and SSS. This isolates the culprit so you can raise exactly the right samples. This targeted approach keeps render time low; a lighter, cleaned-up scene helps too, just like keeping a drawing file lean by reducing an AutoCAD file with PURGE.

A denoiser removes the last noise without you having to increase samples further.

The quickest gain often lies not in more samples but in a denoiser: a filter that strips the remaining noise from the image. Arnold for 3ds Max offers three options, each with its own use:

For the Arnold Denoiser (Noice), turn on Output Denoising AOVs on the Denoiser tab of Render Setup; Arnold will automatically generate the required normal, depth and albedo passes and the variance data. You render to EXR and then run the denoiser. Noice doesn’t work on the GPU; use OptiX or OIDN there. OptiX is intended for fast previews in the interactive render, OIDN for a clean post-process on stills.

A denoiser can significantly lower the number of samples needed, so you get a clean final image even with a lower Camera (AA). The official explanation is in the Arnold documentation on removing noise.

Arnold GPU speeds up setup, but be sure of final quality on the CPU.

Arnold can render on the CPU or on the GPU (Arnold GPU). You choose the render type in Render Setup under Render Device. The GPU is much faster in interactive rendering, so you see the effect of your sample and light settings almost instantly. That makes it ideal for building the scene and roughly assessing noise.

There are differences, though. Not every feature is identically supported on the GPU, and the video card’s memory is more limited than system memory. For final frames, therefore, check the result on the CPU, or carefully test whether the GPU produces exactly the same image. A handy workflow: build and tweak with the GPU and the OptiX denoiser for speed, and render the final on the CPU with the Arnold Denoiser for reliability.

Keep the scene itself light, too. Unnecessarily heavy textures, extremely high subdivisions and superfluous objects lengthen every test render. Regularly clean up your scene, similar to keeping a drawing file lean, and you’ll gain time with every iteration.

Work from coarse to fine: first samples, then targeted adjustments, then denoise.

An efficient sequence gives a clean image without unnecessary render time:

1. Turn on Adaptive Sampling and start with a low Camera (AA), for example 3, and a generous Max. Camera (AA).
2. Reduce the Adaptive Threshold until the general noise is acceptable.
3. Keep Ray Depth as low as the scene permits.
4. Enable clamping against fireflies.
5. Render AOVs to isolate remaining noise and increase only the relevant samples.
6. Apply a denoiser for the final clean-up.

Always test at a low resolution or a small render region before you run the full frame. That way you quickly see the effect of each change. If you work with rented render licences or a render farm, keep an eye on the licence type; the overview on the difference between OEM, retail and volume licences explains what that means for rendering on multiple machines.