Visible to ...

You can selectively disable an object's visibility for the various types of rays in the renderer. By default, objects are visible to all types of rays. Camera - Camera (AA) rays (i.e., primary or view rays). Shadow - shadow rays fired in the direct lighting calculations. Specular - specular_reflection rays. Transmission - transmission rays. Diffuse - indirect_diffuse rays (i.e. global illumination or GI rays). Specular - indirect_specular rays (i.e. specular reflection rays).

To set the visibility, add up the values of the rays you want to "see" the object.

For example, if an object is visible to the camera (primary visibility), and to transmission (both diffuse and specular), then that’s visibility 13 (1 + 4 + 8).


Ray typeDecimal Value
Camera (Primary Visibility)1
Shadow (Casts Shadows)2
Diffuse transmission4
Specular transmission8
Volume16
Diffuse reflection32
Specular reflection64
SSS (subsurface)128

Camera Rays

Determines whether the object is visible to camera rays.

The tank in this example is invisible to camera rays but visible to all other types of rays, including shadow rays

Shadow Rays  

Determines whether the object is visible to camera rays.

The tank in this example is invisible to camera rays but visible to all other types of rays, including shadow rays

Diffuse Transmission Rays

Object is visible in diffuse transmission and subsurface scattering. 

Specular Transmission

Object is visible in sharp and glossy specular transmission (refraction).

Diffuse Reflection

Affects indirect diffuse rays (i.e., global illumination, hemi, or GI rays).

Specular Reflection

You can selectively disable an object's visibility for the various types of rays in the renderer. By default, objects are visible to all types of rays. Specular Reflection visibility affects indirect specular rays (i.e., specular reflection rays).

Volume Scattering

Object is visible in indirect volume rays.

Receive Shadows

Determines whether or not the object picks up shadows from other objects.

Self Shadows

Determines whether or not the object casts shadows on itself.


Opaque

As of Arnold 5.3, this flag is set automatically by changing the opacity or transmission on a material.

Determines whether the object is considered opaque (transparent). By default, Arnold built-in shaders set the opaque flag automatically, based on whether or not the shader settings would require disabling the opaque flag on the object to render correctly. For example, it's no longer necessary to manually disable the opaque flag to get transparent shadows for a glass shader.


Exceptions are curves and points when min_pixel_width is in use, and OSL shaders.  



More information about Transmission and Opacity can be found here.

Matte

When enabled, this turns an object or group into a holdout matte. It affects primary rays only. The matte color is always black, and the opacity of the object is preserved. Shaders will not run on the object anymore and it will output all-black (including the alpha), except if the opaque parameter is off, in which case shaders will be run just to compute the opacity. Note that even AOVs output by its shaders in this case will be black.

The Matte attribute does not matte out the AOV contributions of built-in AOVs such as P, N, and raycount.

There is also the option to create a matte with a Matte shader.

Trace Sets

Use this field to tag objects to belong to one or many trace sets. Trace Sets require a custom shader or the Trace Set shader to be used.

This string label defines the set of objects to be traced or avoided. Objects are labeled using the Arnold shape attributes.

  • When a trace set is exclusive, rays are traced against all geometry except the tagged nodes.
  • When a trace set is inclusive, rays are traced against tagged nodes, but also against nodes that are not tagged at all.
  • An empty trace set name means that the shape belongs to all sets. So to remove objects from, say reflections, one must assign a dummy set name.
  • The trace set name must be set before the ray is fired. For example, for "direct" reflections, the trace_set node must be connected to the "camera" rays in addition to the "reflection" one.

SSS Sets

It is possible to tag multiple objects as belonging to the same SSS 'set' so that illumination will blur across object boundaries. A common use case might be blurring between teeth and gum geometry. It is enabled by adding the constant STRING userdata sss_setname to the same value on the objects in the set.

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