RTX - Real-Time mode#
Omniverse RTX Renderer provides the RTX - Real-Time ray tracing mode which allows rendering more geometry than traditional rasterization methods as well as physically based materials at a high fidelity, in real-time.
In RTX - Real-Time mode, the renderer performs a series of separate passes that compute the different lighting contributions (for example: ray-traced ambient occlusion, direct lighting with ray-traced shadows, ray-traced indirect diffuse global illumination, ray-traced reflections, ray-traced translucency and subsurface scattering). Each pass is separately denoised, and the results are composited.
This mode is slightly less accurate than RTX – Interactive (Path Tracing) mode, due to using various shading approximations and optimizations to maintain a high framerate.
Eco Mode#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
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ECO Mode |
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Pauses frame rendering automatically to reduce GPU usage. This can be particularly useful to reduce power consumption on laptops. |
Stop Rendering After This Many Frames Without Changes |
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Frame rendering is paused after this many frames without changes, and will resume when a change occurs. |
NVIDIA DLSS#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Frame Generation |
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DLSS Frame Generation boosts performance by using AI to generate more frames. DLSS analyzes sequential frames and motion data to create additional high-quality frames. This feature requires an Ada Lovelace architecture GPU. |
Super Resolution |
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Choose between two AI-based algorithms to improve image quality.
- DLSS (3): Boosts performance by using AI to output higher resolution frames from a lower resolution input. DLSS samples multiple lower resolution images and uses motion data and feedback from prior frames to reconstruct native quality images.
- NVIDIA DLAA (4): Provides higher image quality with an AI-based anti-aliasing technique. DLAA uses the same Super Resolution technology developed for DLSS, reconstructing a native resolution image to maximize image quality.
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Select between Performance, Balanced, Quality, or Auto modes.
- Auto (3): Selects the best DLSS Mode for the current output resolution.
- Quality (2): Offers higher image quality than balanced mode.
- Balanced (1): Offers both optimized performance and image quality.
- Performance (0): Offers a higher performance boost than balanced mode.
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Direct Lighting#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Direct Lighting |
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Enable direct light contributions from lights. |
Samples per Pixel |
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Higher values increase the direct lighting quality at the cost of performance. |
Max Ray Intensity |
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Clamps the brightness of a sample, which helps reduce fireflies, but may result in some loss of energy. |
Mesh-Light Sampling |
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Enables direct illumination sampling of geometry with emissive materials. |
Shadows |
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When disabled, lights will not cast shadows. |
Indirect Diffuse Lighting#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Indirect Diffuse GI |
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Enables Diffused Global Illumination. |
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Higher values result in smoother looking GI. |
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More bounces allow more potential GI contribution in occluded areas. |
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Controls the intensity of the GI contribution evenly across the occluded area. |
Ambient Occlusion |
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Enables ambient occlusion. |
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The radius around the intersection point which the ambient occlusion affects. |
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Minimum number of samples per frame for ambient occlusion sampling. |
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Maximum number of samples per frame for ambient occlusion sampling. |
Ambient Light Color |
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Color of the global environment lighting. |
Ambient Light Intensity |
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Brightness of the global environment lighting. |
Reflections#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Reflections |
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Enables reflections. |
Samples per Pixel |
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Higher values increase the reflections quality at the cost of performance. |
Max Ray Intensity |
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Clamps the brightness of a sample, which helps reduce fireflies, but may result in some loss of energy. |
Max Bounces |
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Number of bounces for reflection rays. |
Roughness Cache Threshold |
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Roughness threshold for approximated reflections. Higher values result in better quality, at the cost of performance. |
Translucency#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Translucency |
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Enables translucency for specular transmissive surfaces such as glass. |
Max Refraction Bounces |
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Number of bounces for refraction rays. |
Reflection Seen Through Refraction |
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When enabled, reflection seen through refraction is rendered. When disabled, reflection is limited to first bounce only. More accurate, but worse performance. |
Fractional Cutout Opacity |
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Enables fractional cutout opacity values resulting in a translucency-like effect similar to alpha-blending. |
Depth Correction for DOF |
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Improves DoF for translucent refractive objects, but can result in worse performance. |
Motion Vector Correction |
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Enables motion vectors for translucent refractive objects, which can improve temporal rendering such as denoising, but can result in worse performance. |
World Epsilon Threshold |
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Threshold below which image-based reprojection is used to compute refractions. Lower values result in higher quality at the cost performance. |
Roughness Sampling |
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Enables sampling roughness, such as for simulating frosted glass, but can result in worse performance. |
Max Ray Intensity |
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Clamps the brightness of a sample, which helps reduce fireflies, but may result in some loss of energy. |
Invisible Light Behind Translucency in Reflections |
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If true, hide light reflection if it is behind translucent geometry. Subject to the roughness thresholds of the light visibility settings. |
Subsurface Scattering#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Subsurface Scattering |
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Enables subsurface scattering. |
Max Sample Per Frame |
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Max samples per frame. |
Firefly Filtering |
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Enables firefly filtering for the subsurface scattering. |
Denoise Irradiance Output |
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Denoise the irradiance output from sampled lighting pass before it’s used. Helps in complex lighting conditions or if there are large area lights which makes irradiance estimation difficult with low sampled lighting sample count. |
Transmission |
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Enables transmission of light through the medium, but requires additional samples and denoising. |
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Transmission sample count per frame. |
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Transmission samples count per BSDF Sample. Samples per pixel per frame = BSDF Sample Count * Samples Per BSDF Sample. |
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Transmission threshold for screen-space fallback. |
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Enables rendering transmission in half-resolution to improve performance at the expense of quality. |
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Enables transmission sample guiding, which may help with complex lighting scenarios. |
Caustics#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
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Caustics |
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Enables simulation of caustics generated for area lights which have the ‘Enable Caustics’ enabled. |
Photon Count Multiplier |
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Factor multiplied by 1024 to compute the total number of photons to generate from each light. |
Photon Max Bounces |
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Maximum number of bounces to compute for each light/photon path. |
Filter Iterations |
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Number of iterations for the denoiser applied to the results of the caustics tracing pass. |
Global Volumetric Effects#
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
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Accumulation Frames |
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Number of frames samples accumulate over temporally. High values reduce noise, but increase lighting update times. |
Depth Slices Count |
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Number of layers in the voxel grid to be allocated. High values result in higher precision at the cost of memory and performance. |
Pixel Density |
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Higher values result in higher fidelity volumetrics at the cost of performance and memory (depending on the # of depth slices). |
Slice Distribution Exponent |
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Controls the number (and relative thickness) of the depth slices. |
Inscatter Blur Sigma |
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Sigma parameter for the Gaussian filter used to spatially blur the voxel grid. 1 = no blur, higher values blur further. |
Inscatter Dithering Scale |
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The scale of the noise dithering. Used to reduce banding from quantization on smooth gradients. |
Spatial Sample Jittering Scale |
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Scales how far light samples within a voxel are spatially jittered: 0 = only from the center, 1 = the entire voxel’s volume. |
Temporal Reprojection Jittering Scale |
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Scales how far to offset temporally reprojected samples within a voxel: 0 = only from the center, 1 = the entire voxel’s volume. Acts like a temporal blur and helps reduce noise under motion. |
Use 32-bit Precision |
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Allocate the voxel grid with 32-bit per channel color instead of 16-bit. This doubles memory usage and reduces performance, generally avoided. |
Flow Sampling |
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Samples density from Flow grid. |
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Min Flow layer to sample, inclusive. |
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Max Flow layer to sample, inclusive. |
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Scale to apply to sampled Flow density. |
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Offset applied after scale. 1.0 allows existing fog to continue working normally. |
Multi-GPU#
Multi-GPU rendering in RTX - Real-Time mode splits the image to render as tiles which are dispatched to the GPUs and then composited into a single image.
The primary GPU performs various tasks, such as: rendering pixels, sample aggregation, denoising, post processing, UI rendering. The default GPU 0 Weight value is usually ideal.
Display Name |
Setting Name |
Value Type |
Default Value |
Description |
|---|---|---|---|---|
Multi-GPU |
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Enables using multiple GPUs. This splits the rendering of the image into a large tile per GPU with a small overlap region between them. |
Automatic Tiling |
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Automatically determines the image-space grid used to distribute rendering to available GPUs. The image rendering is split into a large tile per GPU with a small overlap region between them. Note that by default not necessarily all GPUs are used. The approximate number of tiles is viewport resolution divided by the Minimum Megapixels Per Tile setting, since at low resolution small tiles distributed across too many devices decreases performance due to multi-GPU overheads. Disable automatic tiling to manually specify the number of tiles to be distributed across devices. |
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The minimum number of Megapixels each tile should have after screen-space subdivision. |
Tile Count |
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Number of tiles to split the image into. Usually this should match the number of GPUs, but can be less. |
Tile Overlap (Pixels) |
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Width, in pixels, of the overlap region between any two neighboring tiles. |
GPU 0 Weight |
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This normalized weight can be used to decrease the rendering workload on the primary device for each viewport in relation to the other secondary devices, which can be helpful for load balancing in situations where the primary device also needs to perform additional expensive operations such as denoising and post-processing. |
Multi-Threading |
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Execute per-device render command recording in separate threads. |
Limitations#
Multi-GPU rendering lowers the cost of rendering more pixels and is ideal for high-resolution rendering, particularly for the RTX Interactive (Path Tracing) mode. It will not improve performance for animations, physics, etc.
For efficiency’s sake, in some contexts rendering will switch to single-GPU automatically until conditions warrant multi-GPU rendering, for example when rendering at low resolution.
Multi-GPU rendering is enabled by default if the system has multiple NVIDIA RTX-enabled GPUs of the same model.
Per-GPU memory usage is limited to 48GB.
Multi-GPU is disabled for mixed-GPU configurations. This can be overridden with a setting. Note that the GPU with the lowest memory capacity will limit the amount of memory the other GPUs can leverage.
GPUs which don’t support ray tracing are skipped automatically.
Note
A GPU information table is logged to the omniverse .log file under [gpu.foundation] listing which GPUs are set as Active. Each GPU has a device index assigned and this index can be used with the multi-GPU settings below.
Setting Name |
Value Type |
Default Value |
Description |
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Specifies if multi-GPU is enabled, but multi-GPU is disabled if the NVIDIA RTX-enabled GPUs are not of the same model; setting this to true will enable multi-GPU anyway. |
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Enables only a subset of GPUs, specified by a comma-separated list of device indices. |
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Specifies the maximum number of NVIDIA RTX-enabled GPUs. GPUs which don’t support ray tracing are skipped automatically. |