How to get rid of excessive noise? Corona for Cinema 4D
Subtle high-frequency noise is normal for Corona and other path-tracing renderers, especially at the beginning of the rendering process. But strong noise that won't go away after many passes, or after a long rendering time, may suggest that the rendering engine encountered some problems in your scene setup. Starting from Corona 1.4 you can use the denoising feature to get rid of the noise by smartly blurring it. It is however recommended to make sure that there are no mistakes in the render setup, or the scene itself.
To efficiently get rid of problematic noise, you need to find out where it comes from. Most common causes of persistent noise include:
Wrong material setup:
This is usually manifested by noise visible only in specific parts of the scene (some objects or some materials).
- How to create basic materials?
- Unrealistic material albedo - see: What is Albedo? How to use it?
- Wrong glass type - see: What type of glass should I use?
- Misuse of Corona Light material or self-illumination- see: Should I use Corona Light material or self illumination?
Noise is visible in strongly lit areas, on edges of light spots or shadows, or when light bounces off objects.
- Small window holes. Always use portals in such scenes - see: How to use light portals in Corona Renderer for Cinema 4D?
- Area lights or global illumination - see: How can I tell whether noise comes from direct or indirect light?
- Caustics - you can usually reduce them using max sample intensity parameter - see: MSI or by using Corona Ray Switch material.
- Using many light sources in a scene - try to reduce the number of lights in your scene or use other lighting techniques (for example emitter objects or texture maps).
Misuse of Corona Light material or self-illumination - see: Should I use Corona Light material or self illumination?
Noise is visible in the whole image or in specific areas like direct light or light bouncing off objects.
- Too high max sample intensity value - see: MSI
- Too high or too low values of GI vs. AA Balance or Light Samples Multiplier
Note: you can easily reset all Corona render settings to their default values - see: How to reset settings to their default values?
Fireflies in corners:
Single bright pixels visible in corners of the room or on geometry without thickness.
Noise in camera effects:
Noise is visible in areas affected by depth of field or motion blur effects.
- Depth of field - see: How to enable and control DoF?
- Motion blur - see: How to enable and control motion blur?
Flickering/splotches in animation:
Apart from user errors, there are some physically-correct phenomena that can also cause "noise" effect in real life (for example in photography). This includes:
- Sunlight or other strong light reflected by grass/leaves/small objects, see: I can see bright pixels in grass!
- High-frequency textures, especially as bump maps or displacement
- Moiré pattern
- To clamp sample intensity, and thus reduce noise visible in highlights (fireflies), you can use MSI and highlight clamping.
To determine the cause of noise, it may be sometimes useful to enable material override (see: How to create clay renders? ). If the noise is still visible after applying the diffuse grey material to all objects, it indicates that most probably it is not caused by scene materials.