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# iray String Options

The iray renderer introduced in 3ds Max 2012 provides some String Options accessible through the same mental_ray_string_options Core Interface used for the mental ray Strings Options featured for the first time in 3ds Max 2011. They can be used to provide some advanced settings not exposed to the standard iray renderer User Interface. For these options to work, the current renderer must be set to iray first. As with mental ray string options, these settings are temporary and will not be saved and loaded with the scene - you will have to re-enable them via MAXScript in the current session.

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CPU Threads GPU Devices Background Color Environment Lighting Environment Dome |

## CPU Threads

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    mental_ray_string_options.AddOption "iray threads" <Integer>threadsCount

Specifies the number of threads to use when rendering on the CPU.

If set to 0, the CPU will be disabled.

If not set, the default behavior is "use all available cores".

## GPU Devices

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    mental_ray_string_options.AddOption "iray devices" <String>devicesToUse

Specifies the GPU devices to use as a string of zero-based Device IDs delimited by spaces, e.g. "0 2" means use the first and third devices (if available).

When not set, the default behavior is to "use no GPU devices".

Be careful not to set both the "iray threads" to 0 and the "iray devices" to "" as iray will have no devices to run on.

## Background Color

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    mental_ray_string_options.AddOption "iray background color" <Point3>backgroundColor

Specifies the background color as a Point3 value representing RGB as floating point numbers in 0-1 range.

When not set, the default background color is black.

## Environment Lighting

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    mental_ray_string_options.AddOption "environment lighting resolution" <Integer>resolution

Specifies the Environment Lighting Resolution as an Integer.

    mental_ray_string_options.AddOption "environment lighting blur" <Boolean>onOff

Specifies whether to blur the Environment Lighting.

When no set, no blurring will be performed.

## Environment Dome

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iray features functionality to use a fake environment dome instead of the infinite environment provided by the environment shader. As this dome is of finite size, camera movements result in positional changes inside the dome and, therefore, the environment lookup changes. Note that the illumination is still computed from the original infinite environment.

    mental_ray_string_options.AddOption "environment dome mode" <String>mode

Specifies the Environment Dome shape.

Possible values are:

"infinite" - default if not specified, standard infinite environment lookup

"sphere" - sphere shaped dome

"hemisphere" - sphere shaped dome where the lower hemisphere is projected on the plane dividing upper and lower hemisphere

    mental_ray_string_options.AddOption "environment dome position" <Point3>position

Specifies the dome position.

    mental_ray_string_options.AddOption "environment dome radius" <Float>radius

Specifies the dome radius.

    mental_ray_string_options.AddOption "environment dome rotation axis" <Point3>axis

Specifies the dome rotation axis.

When the dome mode is enabled, an additional "shadow catcher" ground plane can be specified. This transparent plane weights the environment lookup behind it using a progressive estimation of the amount of shadow (for direct light) the ground plane point would receive from the objects in the scene. It can then be used to catch shadows of an object, while the ground still is the environment lookup as specified by the dome settings. The ground plane is specifiied with the following options:

    mental_ray_string_options.AddOption "environment dome ground" <Boolean>onOff

Specifies whether to use the Environment Dome Ground (Shadowcatcher).

    mental_ray_string_options.AddOption "environment dome ground position" <Point3>position

Specifies the position of the Environment Dome Ground.

    mental_ray_string_options.AddOption "environment dome ground glossiness" <Float>glossiness

Specifies the glossiness of the Environment Dome Ground.

    mental_ray_string_options.AddOption "environment dome ground reflectivity" <Point3>reflectivity

Specifies the reflectivity of the Environment Dome Ground as a Point3 value. A value of [0,0,0] will turn the reflectivity off, a value of [1,1,1] will make the ground fully reflective for all three color components, a value of [1,0,0] will tint the reflection into Red only and so on.

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#### See Also

- Interface: mental_ray_string_options

- iray_Renderer Renderer Class