Image based lighting node attributes

These are descriptions of the attributes in the mental ray IBL (Image Based Lighting) node. See Image-based lighting (sky-like illumination) and also Render infinitely distant (sky-like) illumination and reflection.

Image Based Lighting Attributes

These are the attributes in the Image Based Lighting Attributes section.

Hardware Filter

Sets texture filter quality for shaded view: nearest or linear.

Hardware Exposure

Hardware Exposure controls gamma for hardware display. Gamma is the overall brightness of an image. Changes to gamma not only adjust the brightness, but also adjust ratios of colors in the image.

A value of 1 means that the color is not adjusted. Increase the value to make the mid-range tones brighter. Decrease the value to make them darker.

Hardware Alpha

Sets transparency of IBL shape locator in shaded view. 0 is transparent, 1 is fully opaque.

Color Gain, Color Offset, Invert, Alpha Is Luminance

These attributes are the same as those of Maya's texture node. They apply in similar ways to IBL.

For more information on texture nodes, see Overview of texture nodes in the Shading guide.


Select a UV space for the environment sphere: spherical (latitude-longitude) or angular (HDR Shop).


Select whether to map a file or a procedural texture as the IBL texture. File textures can be previewed interactively. See also Texture.

Image Name

Name of image on disk. Click the browse button to browse to the file.

Use Frame Extension

If turned on, the texture's file name may change on a per-frame basis. This is used to load an image sequence instead of a single file.

Frame Extension

The frame extension.


If Type is set to Procedural, connect a 2D texture shading network to this input.


The default value for this attribute is on, and results in the default IBL behavior.

If you turn this attribute off, IBL switches to Finite mode. In Finite mode, IBL behaves as a finite sphere, where translation and uniform scaling are supported. Photon and light emission behave as point lights, not directional lights, so that IBL can be used for closed environments. To avoid artifacts, ensure that your IBL sphere encloses your entire scene.

  • In Finite mode, IBL may take more time to compute.
  • Toggling between infinite and finite may cause illumination to change (similar to toggling between point and spot lights).

Render Stats

Controls the IBL texture's visibility to certain ray types. This maps to a camera environment shader in mental ray. If all controls are deactivated, then no environment shader is processed. For classical image based lighting, the IBL texture must be visible to final gather rays. and Final Gathering must be on.

Primary Visibility

When on, the surface is visible in the view and renders.

Visible as Environment

When on, the surface is visible to environment rays (direct reflection of the environment). This attribute is off by default, unless you created the IBL node from the mental ray Render Settings window.

Visible in Secondary Reflections

When on, the surface is visible to secondary reflection rays. This attribute is off by default, unless you created the IBL node from the mental ray Render Settings window.

Visible In Refractions

When on, the surface refracts in transparent surfaces.

Visible In Final Gather

When on, the surface is visible to Final Gather rays and is used to illuminate the scene. When off, IBL does not affect final gathering. This attribute is off by default, unless you created the IBL node from the mental ray Render Settings window.

Light Emission

These are the attributes in the Light Emission section.

You can emit light from the IBL environment radially inward toward the origin (of world space). If light emission is turned on, the IBL node acts like true light sources in the scene. The IBL texture is mapped to a mental ray light shader just like a real light source would be.

Emit Light

Turn on, if you want to emit light from the infinitely distant IBL environment.

Quality U, Quality V

The light shader sets up a “control texture” for light emission. Every pixel in that texture virtually represents a directional light. These values specify the control texture's resolution. Higher values offer more precision but are more processor intensive. Loaded IBL textures are downsampled to the filter resolution; procedural textures are sampled at this resolution in pixel units for optimum performance.


Sampling all “directional lights” represented by the control texture is often prohibitively expensive. Therefore the shader has a built-in importance mechanism that attempts to select the primary (key) lights.

The first Samples parameter specifies the number of important lights that must be sampled. The second parameter quasi-randomly selects a certain number of secondary (fill) lights.

Low samples

Low Samples specifies the number of light samples taken from IBL during final gathering. It defaults to 1/8th of the regular samples (that is, 5/2).

Vary Focus

Each “directional light” in the control texture sphere determines its direction. Turning on Vary Focus slightly offsets that direction (randomly) and thus improves quality.

Disable Backlighting

If lights on the backside of surfaces do not contribute to the surfaces' illumination (i.e., there is no translucency in the scene), you should turn this on. It optimizes sampling significantly.

Emit Diffuse, Emit Specular, Use Ray Trace Shadows, Shadow Color, Ray Depth Limit

These parameters are identical to attributes on Maya's standard lights.

Photon Emission

These are the attributes in the Photon Emission section.

Photons can be emitted from the IBL environment sphere. This requires Global Illumination and, or Caustic photons to be turned on in the Render Settings window. The emission direction is chosen randomly for individual photons. Similar to light emission, a photon picks up the color based on its emission direction from the IBL texture (file or procedural), possibly adjusted by color gain and offset. The results of this maps to a mental ray photon emission shader.

Emit Photons

Turn on, if you want to emit photons from the infinitely distant IBL environment.


Determines how many global illumination photons are emitted.

Caustic Photons

Determines how many caustic photons are emitted.


Determines the exponent used for photon emission.

Standard emission

If off, photons will be stored on first hit. This is useful if IBL is to be achieved using global illumination photons alone. In terms of a real-world environment you can think of this switch as photons from the Sun being scattered in the atmosphere before reaching any surface.

Turn this option on, if you are emitting caustic photons, or if you are emitting light in combination with photons.