Troubleshooting direct, indirect, and environment noise

Fix issues causing speckled noise in lit scenes.

Cause

Example: All sample counts are set to 8 (left). All sample counts are set to 2048 (right).

The Progressive Lightmapper is a Monte Carlo path tracer. Insufficient ray counts lead to noisy lightmaps, and increasing the number of rays the lightmapper spawns from each lightmap texel helps to reduce the noise in the lightmaps.

Resolution

To fix the issue of too much noise, you can increase the sample size from direct, indirect, and environment sources to reduce lightmap noise, and use denoiser and filters. Note that when increasing samples, this will increase bake times in a linear fashion.

Note: To make easier to debug issues, got to the Lighting window, and set the Filtering property to None.

Increase direct samples

Direct samples control the number of rays, which the lightmapper shoots towards light sources.

Example: Scene lit only by direct light. Direct samples are set to 8 (left). Direct samples are set to 2048 (right).

Use this method of increasing direct samples if:

• Objects lit by area lights produce noisy soft shadows.
• Baked lights with a modified Baked Shadow Angle value are producing noisy results.

Increase indirect samples

Indirect samples control the number of paths, which the lightmapper shoots towards the GI contributors in the scene.

Example: Scene lit only by the indirect bounce light. Indirect samples are set to 8 (left). Indirect samples are set to 2048 (right).

Once these paths intersect geometry, texels spawn rays towards:

• Environment, which makes it an indirect environment sample.
• A light source, which makes it an indirect lighting sample.

Paths can bounce off surfaces. Some ways Unity can end a path are:

• Once it reaches the Max Bounces value.
• If it doesn’t intersect any geometry.
• By the Russian roulette algorithm.

Use this method of increasing indirect Samples if:

• Indirectly lit areas are noisy.
• Objects using emissive materials produce a lot of noise.

Increase environment samples

Environment samples control the number of rays, which the lightmapper shoots towards the sky/environment.

Example: Scene lit only by environment lighting. Environment samples are set to 8 (left). Environment samples are set to 2048 (right).

Use this method of increasing environment samples if:

• Baked environment/HDRI produces noisy results.

Note: that you would need to disable all lights in the scene to verify this.

Use denoising and filtering

Unity can apply a post-processing step to remove noise by using filtering or machine learning denoisers.

To enable filtering, navigate to the Lighting window (menu: Window > Rendering > Lighting) and select the Filtering property, and select from three options:

• None - Disables filtering and denoising.
• Auto - Attempts to select the best filtering and denoising option based on current system configuration.
• Advanced - Allows users to fine-tune filtering and denoising properties.

Available filters:

• Gaussian - Applies a bilateral filter (blur) to the lightmap. This smoothens noise at the expense of visual fidelity. Increase radius parameters to increase filtering strength. High values can lead to leaking artifacts.
• A-Trous - Edge-aware filter which attempts to remove noise, while maintaining edge definition. Works well with high sample counts and in conjunction with denoising. Doesn’t work well with noisy HDR lightmaps.

Available machine learning denoisers:

• Open Image Denoise (OIDN) - Machine learning denoiser from Intel. Vendor agnostic. Works on Windows, macOS, and Linux platforms.
• Optix - Machine learning denoiser from Nvidia. Works only with Nvidia GPUs. Supports Windows only.
• RadeonPro - Machine learning denoiser from AMD. Vendor agnostic. Works on Windows and Linux.

Experiment with different denoiser and filtering combinations to achieve the best results for your project.