RTX Accurate (Iray) Settings

Overview

NVIDIA RTX Accurate (IRay) is the Omniverse integration of the NVIDIA Iray® SDK . It is a push-button, physically based rendering technology that generates photorealistic imagery for interactive and batch rendering workflows. RTX Accurate (IRay) is used to create predictive imagery if you grant a renderer more time to cut less corners.

NVIDIA RTX Accurate (IRay) uses the same MDL material description as our other RTX renderers but delivers the most physically accurate results for light simulation.

Device Settings

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

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

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 Irradiance: 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.

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

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

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.