Real-Time Path Tracing#
Real-Time Path Tracing (RTPT) is the default render mode. It renders global illumination, reflections and shadows, using cached lighting to reduce the work per frame.
Select RealTimePathTracing on the RenderProduct. See Render Modes
for equivalent USDA and Python authoring examples.
See Outputs for this mode’s outputs, including SelectionState for
custom selection drawing with SPG.
DLSS Frame Generation#
DLSS Frame Generation inserts interpolated color frames between simulated frames for smoother presentation.
Settings#
Sampling and Caching#
USD declaration |
Description |
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Enables caching path-tracing results for improved performance at the cost of some accuracy. |
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Enables the many-light sampling algorithm, which can improve performance in scenes with many lights. |
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Enables direct illumination sampling of geometry with emissive materials. See Mesh Lights. |
Ray Bounces and Shading#
omni:rtx:rtpt:maxBounces#
Maximum number of ray bounces for any ray type. Higher values give more accurate global illumination, but worse performance.
uint | Default: 3
omni:rtx:rtpt:extraSpecularAndTransmissiveBounces#
Additional number of specular and transmission ray bounces beyond maxBounces. Affects reflections and refractions through transparent materials like glass.
uint | Default: 0Other Ray Bounce and Shading Settings#
USD declaration |
Description |
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Maximum number of ray bounces for subsurface scattering (SSS). |
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If enabled, fractional cutout opacity values are treated as a measure of surface ‘presence’, resulting in a translucency effect similar to alpha-blending. |
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Roughness threshold above which a surface is considered rough and rendered with performance-favoring approximations. |
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Enables motion vectors for translucent (refractive) objects, which can improve temporal rendering such as denoising but can reduce performance. |
Material Transmission Override#
Real-Time Path Tracing analyzes materials to identify surfaces that light can pass through, using known parameter names and their values to refine the classification. For example, RTPT can trace an extra ray past a glass surface to collect depth, normals, and material data from the object behind it. This lets screen-space subsurface scattering operate on that object instead of the glass. The classification also affects opaque-only XR depth and translucent-pixel compositing; it does not change the material’s transmission shader.
Parameter matching works for built-in materials with recognized parameters, but
custom MDL and MaterialX materials may use parameters the renderer does not
recognize. In those cases, use omni:rtx:enableTransmission to override the
automatic translucency classification.
Author the custom boolean attribute on the bound Material prim, not on its Shader child, geometry, or RenderProduct.
To clear the material’s translucency flag, add this declaration inside the existing Material prim:
custom bool omni:rtx:enableTransmission = false
For specular translucency, the override applies only when the material is already
classified as translucent and no recognized transmission-driving parameter is found. Recognized parameters
take precedence, including enable_specular_transmission, transmission_factor,
registered specular-transmission parameters, and transmission_color_texture
when transmission_color is zero. For those materials, change the shader’s
transmission inputs instead.
Leave the attribute unauthored to use the material-derived classification. Setting
it to true retains existing translucency; it cannot make a non-translucent
material transmissive.
Setting the attribute to true also clears a diffuse-transmissive material’s
diffuse-transmission flag when the material has no enable_diffuse_transmission
parameter. Leave the attribute unauthored to preserve that automatic classification.
Note
This changes material classification, not the shader’s transmission behavior.
It does not disable transmission in Path Tracing (PT). Setting it to false
also does not disable diffuse transmission or cutout opacity.
Firefly Filter#
USD declaration |
Description |
|---|---|
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Enables the firefly filter. |
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Clamps the maximum ray intensity for glossy bounces. Can help prevent fireflies, but can result in energy loss. Automatically scaled with exposure. |
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Clamps the maximum ray intensity for diffuse bounces. Can help prevent fireflies, but can result in energy loss. Automatically scaled with exposure. |
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Clamps the maximum ray intensity for emissive contribution after primary bounce. Can help prevent fireflies, but can result in energy loss. Automatically scaled with exposure. |
Gaussian Splatting#
See Gaussian Splats for ParticleField authoring and runnable examples.
USD declaration |
Description |
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When enabled, Gaussian hit depth is opacity-weighted across up to |
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When enabled, Gaussian SH0 albedo is opacity-weighted across up to |
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Total hit budget for Gaussian depth/albedo accumulation. Values up to 48 use a single pass over the closest N hits. Values above 48 enable a multi-batch traversal that continues until the budget is reached, the 95% opacity threshold is hit, or no more candidates are found. Set to -1 for unlimited accumulation (stops only on opacity threshold or no remaining intersections). Set to 0 to disable accumulation entirely (depth/albedo accumulation settings are ignored). |
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When enabled, RTPT deterministically composites Gaussians in supported ParticleFields for primary camera rays instead of using stochastic transparency. This requires inline Gaussian tracing. Pipeline fallback, secondary rays, spectral materials, and shadows remain stochastic. At most three overlapping ParticleFields are composited. |