General Properties

The following settings are provided via the Arnold Properties Modifier object modifier for geometry objects.

Visibility

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).

Camera (Primary 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 Reflections

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

Sphere has 'Visible in Diffuse' enabled	Sphere has 'Visible in Diffuse' disabled

Specular Reflections

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).

Enabled	Disabled

Diffuse Transmission

Object is visible in diffuse transmission and subsurface scattering. 

Specular Transmission

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

Volume Scattering

Shadows

Cast Shadows

Enables the computation of shadows cast from the light. 

Enabled (default)	Disabled

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.

Disabled	Enabled

General

Double-Sided

Just like you can disable the visibility for specific ray types, you can also change an object's sidedness depending on the ray type. By default, objects are double-sided for all rays. By unclicking any of these checkboxes, the object will become single-sided, which means that those parts of the object whose normal vector points away from the incoming ray direction will not be rendered.

Invert Normals

Invert normals (so that normals face inwards and not outwards).

Opaque

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.  

Enabled	Disabled

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.

Disabled	Enabled

Standard Surface shader with 50% opacity	Alpha mask showing 50% opacity

Trace Sets

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.