Caminhos de luz

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Render ‣ Light Paths

Ray Types

Ray types can be divided into four categories:

  1. Camera: the ray comes straight from the camera.

  2. Reflection: the ray is generated by a reflection off a surface.

  3. Transmission: the ray is generated by a transmission through a surface.

  4. Shadow: the ray is used for (transparent) shadows.

Reflection and transmission rays can further have these properties:

  • Diffuse: the ray is generated by a diffuse reflection or transmission (translucency).

  • Glossy: the ray is generated by a glossy specular reflection or transmission.

  • Singular: the ray is generated by a perfectly sharp reflection or transmission.

The Light Path node can be used to find out the type of ray the shading is being computed for.

../../../_images/render_cycles_introduction_rays.svg

Veja também

The object ray visibility settings.

Bounce Control

O número máximo de rebatimentos de luz pode ser controlado manualmente. Enquanto idealmente isso deve ser infinito, na prática um número menor de rebatimentos pode ser suficiente, ou algumas interações de luz podem ser deixadas de fora intencionalmente para convergência mais rápida. O número de rebatimentos de reflexões difusas, reflexões de polimento e transmissão também pode ser controlados individualmente.

Light paths are terminated probabilistically when specifying a minimum number of light bounces lower than the maximum. In that case, paths longer than minimum will be randomly stopped when they are expected to contribute less light to the image. This will still converge to the same image, but renders faster while possibly being noisier.

Transparência

The transparent BSDF shader is given special treatment. When a ray passes through it, light passes straight on, as if there was no geometry there. The ray type does not change when passing through a transparent BSDF.

Alpha pass output is also different for the transparent BSDF. Other transmission BSDFs are considered opaque, because they change the light direction. As such they cannot be used for alpha-over compositing, while this is possible with the transparent BSDF.

Note that, while semantically the ray passes through as if no geometry was hit, rendering performance is affected as each transparency step requires executing the shader and tracing a ray.

Settings

Max Bounces

Total

Maximum number of light bounces. For best quality, this should be set to the maximum. However, in practice, it may be good to set it to lower values for faster rendering. A value of 0 bounces results in direct lighting only.

Diffuse

Maximum number of diffuse bounces.

Glossy

Maximum number of glossy bounces.

Transparência

Maximum number of transparency bounces.

O número máximo de rebatimentos transparentes é controlado separadamente de outros rebatimentos. Também é possível usar terminação probabilística de rebatimentos transparentes, o que pode ajudar na renderização de muitas camadas de transparência.

Transmission

Maximum number of transmission bounces.

Volume

Maximum number of volume scattering bounces.

Clamp

Clamp Direct

This option limits the maximum intensity a sample from rays which have not yet bounced can contribute to a pixel. It reduces noise at the cost of accuracy. Setting this option to 0.0 disables clamping altogether. Lower have a greater affect (dimmer samples) on the resulting image than higher values.

Nota

This option provides a way to limit Fireflies. However, note that as you clamp out such values, other bright lights/reflections will be dimmed as well.

Care must be taken when using this setting to find a balance between mitigating fireflies and losing intentionally bright parts. It is often useful to clamp indirect bounces separately, as they tend to cause more fireflies than direct bounces. See the Clamp Indirect setting.

Clamp Indirect

The same as Clamp Direct, but for rays which have bounced multiple times.

Caustics

A common source of noise is Caustics.

Veja também

See Reducing Noise for examples of the clamp settings in use.

Filter Glossy

When using a value higher than 0.0, this will blur glossy reflections after blurry bounces, to reduce noise at the cost of accuracy. 1.0 is a good starting value to tweak.

Some light paths have a low probability of being found while contributing much light to the pixel. As a result these light paths will be found in some pixels and not in others, causing Fireflies. An example of such a difficult path might be a small light that is causing a small specular highlight on a sharp glossy material, which is observed through a rough glossy material. In fact in such a case there practically occurs a caustic.

With path tracing it is difficult to find the specular highlight, but if you increase the roughness on the material, the highlight gets bigger and softer, and so easier to find. Often this blurring will hardly be noticeable, because it is blurred by the material anyway, but there are also cases where this will lead to a loss of detail in lighting.

Caustics
Reflective

While in principle path tracing supports rendering of caustics with a sufficient number of samples, in practice it may be inefficient to the point that there is just too much noise. This option can be unchecked, to disable reflective caustics.

Refractive

The same as above, but for refractive caustics.