Iray Render Settings

Overview

NVIDIA® Iray® is a push-button, physically based rendering technology that generates photorealistic imagery for interactive and batch rendering workflows. Iray is used to create predictive imagery if you grant a renderer more time to cut less corners.

Iray is using the same MDL material description as our RTX renderers but uses some proprietary structures, so please give it a little bit time for startup when you switch to this renderer.

Device Settings

../_images/iray_device-options.png

Setting

Effect

CPU Enabled

Uses the CPU in addition to GPUs to contribute to the rendering.

GPU#

Depending on the number of GPUs listed in this section the user can switch on/off a GPU.

Scheduler Settings

../_images/iray_scheduler-options.png

Setting

Effect

Scheduler Mode

Selects the scheduler mode.
Interactive Mode updates the Viewport more frequently to enhance interactivity.
Final Frame Mode updates are less frequently to decrease render time for large animations.

Samples Limit

Sets the number of iterations to generate the final image.
The more iterations are chosen - the less noise will remain.
A value of -1 indicates that the rendering goes on forever until a scene operation triggers a restart of the rendering.

Quality Limit Enabled

Only available in “Final Frame” mode. The system tries to figure out when the quality is good enough and no
artifacts are visible anymore. This can lead to varying render times, depending on the complexity of the scene for a single frame and especially
for animation rendering.

Quality Limit

The value for the Quality that one wants to achieve.

Samples per Frame

Instead of displaying every iteration (sample) immediately Iray calculates additional iterations and then displays the result.
This enhances the quality at the cost of longer render times.

Render Settings

../_images/iray_render-options.png

Setting

Effect

Canvas

Selects the output buffer aka AOV (Arbitrary output variables). Some of them use Light path expressions and if they do, light path expression (LPE) is displayed and can be edited.
Iray renders these buffers in parallel:
Beauty: The final rendering you normally want to see
Diffuse: An LPE that displays the diffuse contribution
Specular: An LPE that displays the specular contribution
Glossy: An LPE that displays the glossy contribution
Emission: An LPE that displays emission values
Custom LPE: Employ your own LPEs. Learn More
Alpha: The alpha channel of the rendered scene
Irradience: Displays the light intensity

Denoiser

Adds the AI based Denoiser to the postprocessing pipeline, producing noise-free images faster.

Caustic Sampler

Adds a more precise way to calculate light effects in refractions and reflections.
Use to increase quality in translucent materials or complex material and lighting conditions.

Light Visible in Primary Rays

Adds the visibility of lights other than emissive geometry. Options are:
Per-Light Enable: Defined in each light respectively.
Force Enable: Enabled for all lights regardless of light settings.
Force Disable: Disabled for all lights regardless of light settings.

Spectral Rendering

Spectral rendering is unique to Iray. It can be used to evaluate materials under defined and different light conditions to make informed decisions about the final appearance.

../_images/iray_spectral-rendering-options.png

Setting

Effect

Spectral Rendering

Switches on spectral rendering
Only use if pipeline is based on spectral input or when using thin-film/dispersion materials, but in general also does not cost much if the scene is reasonably complex.
Spectral definition will be required for light sources and materials to yield quality results.
When enabled, additional settings (below) will become available.

Conversion Color Space

For the conversion of color data to spectra, the rendering core needs to know the
color space the data is defined in. Supported color spaces are:
CIE XYZ (xyz)
Rec.709/linear sRGB (rec709)
Rec.2020 (rec2020)
ACES2065-1 (aces)
ACEScg (acescg)
Note: This option also comes into play when spectral data is used without spectral rendering enabled.
In these cases, it defines the conversion of spectra to colors to be used for rendering.

Conversion Intent

If color data is used in spectral rendering it needs to be converted to spectral data.
This conversion is ambiguous in the sense that for a given color there typically are infinitely many
spectra that yield that color (metamers). Fundamentally, the conversion in Iray Photoreal is driven
by the goal of yielding smooth spectra with some flexibility to steer the details for reflection colors.
Natural: Smoothness is preferred over reflectivity. As input colors approach the edge of the gamut,
the intensity of the resulting spectrum necessarily decreases. Consequently, highly reflective saturated
colors may render darker when spectral rendering is enabled.
Faithful: Sacrifice some smoothness to yield greater compatibility with color rendering
Note: This option only has an effect if “Conversion Color Space” is “rec709”.
For other spaces, the behavior is similar to “natural”.

Color Matching

By default the photometric rendering mode uses the CIE 1931 2 degree standard observer as color matching
functions. Setting this option to cie1964, the color matching functions can be changed to the CIE 1964
10 degree standard observer.

Matte Ground Plane Settings

../_images/iray_matte-ground-plane-options.png

Setting

Effect

Enable

Switches on the Matte ground plane that allows for adding an invisible shadow catcher plane and/or reflection plane. If switched on the parameters (below) are exposed.

Reflectivity

Enter a value from 0 to 1 into the RGB field to control how reflective the plane is.

Glossiness

Controls the glossiness/roughness of the ground plane.

Shadow Intensity

Move the slider or enter a value to control the intensity of the shadow being cast on the fake ground plane.

Position

Let you enter the position of the “fake” ground plane.

Rotation Axis

Grants rotational control of the “fake” ground plane.

Environmental Rotation

Drives the orientation of the environment.

Advanced

../_images/iray_advanced-options.png

Setting

Effect

Enable

Limits the number of light path bounces.
The default is 23, but this value can be lowered to speed up rendering performance at the price of correctness of the scene.

Firefly Filter

Compensates very bright pixels (fireflies) that appear often in path-traced renders. Disable if going for physically correct rendering and enable the caustic sampler instead.

Instancing

Configures the use of the RTX BVH acceleration structures.
off: Increases render speed at the price of memory and slower preprocessing/interactive performance (very scene dependent though).
on: Better interactivity when moving objects and memory saving with instanced objects
auto: Let the system automatically choose the “best” setting.

Environment Resolution

Environment dome baking resolution/quality.

Smooth Shadow Terminator

Reduces facets/artifacts present in coarsely tessellated geometry

Max value for “Samples per frame”

Drives the max value for the setting in the Sampler Settings. We limited this to avoid a non responsive system.

Texture compression

Allows compression to save system memory. Higher compression saves more memory at the cost of quality. Medium quality is recommended for most scenes.