RTX Interactive (Path Tracing) Settings

RTX Interactive specific render settings.

Anti-Aliasing

Setting	Effect
Anti-Aliasing Sample Pattern	Sampling pattern used for the purposes of Anti-Aliasing. Select between Box, Triangle, Gaussian and Uniform
Anti-Aliasing Radius	Radius, in pixels, of the sampling footprint to use when generating samples with the selected antialiasing sample pattern

Firefly Filtering

Setting	Effect
Firefly Filtering	Enables logic to reduce the occurrence of “firefly” artifacts
Max Ray Intensity Glossy	The maximum light intensity (in radiance units) that can be contributed along any one ray for glossy events (when the firefly filter is enabled)
Max Ray Intensity Diffuse	The maximum light intensity (in radiance units) that can be contributed along any one ray for diffuse events (when the firefly filter is enabled)

Path-Tracing

Setting	Effect
Max Bounces	Maximum number of bounces in a path
Max Specular and Transmission Bounces	Maximum number of bounces for specular and transmission events
Max SSS Volume Scattering Bounces	Maximum number of bounces for subsurface scattering within a volume
Max Fog Scattering Bounces	Maximum number of bounces for volume scattering within a fog volume
Max Heterogeneous Volume Scattering Bounces	Maximum number of bounces for heterogeneous volumes
Samples per Pixel per Frame (1 to 32)	Total number of samples used for each rendered pixel in one frame update
Total Samples per Pixel (0 = inf)	Maximum number of samples to accumulate per pixel. When this sample count is reached the rendering stops and the same image is displayed until a scene or setting change is detected, causing the rendering process to restart. Set to 0 to remove this limit.
Enable Fractional Cutout Opacity	If enabled, fractional cutout opacity values are treated as a measure of surface ‘presence’, resulting in a translucency effect similar to alpha-blending. Path-traced mode uses stochastic sampling based on these values to determine whether a surface hit is valid or should be skipped.
Reset Accumulation on Time Change	If enabled, the Path-Tracer accumulation is restarted every time the MDL animation time changes. Settings this to false is useful to prevent accumulation reset at every frame when the ‘animation time’ is changing every frames using wallclock time (which can be the case when we an animation is not being played, and wallclock time is used instead of animation time)

Note

While using a higher number of bounces increases accuracy of the final image, it can quickly reduce performance while achieving diminishing returns in terms of image quality.

Sampling & Caching

Setting	Effect
Enable Caching	Enables a technique that caches path tracing results for improved performance at the cost of some correctness.
Enable Many-Light Sampling	Enables a technique that improves the sampling quality (and therefore rendering convergence) in scenes with many light primitives

Denoising

Setting	Effect
Denoising	Enable to apply the OptiX Denoiser to the radiance image generated by the renderer. The OptiX denoiser results in an order of magnitude reduction in rendering times for a target image quality.
Optix Denoiser Blend Factor	A blend factor indicating how much to blend the denoised image with the original non-denoised image. A value of 0 shows only the denoised image, while a value of 1.0 shows the image with no denoising applied.

Path-Traced Fog

Setting	Effect
Path-Traced Fog	Enables Path-Traced fog using volume absorption and scattering simulation with a Henyey-Greenstein phase function The number of bounces is controlled by Max Fog Scattering Bounces
Density	The density of the fog medium
Height	The maximum height of the fog volume
Falloff	Exponential fall-off of the fog
Color	The color of the fog medium
Asymmetry (g)	The asymmetry of the Henyey-Greenstein phase function (“g” parameter)
Use +Z Axis for Height	If set the volume height is considered along the positive Z. Otherwise use the positive Y axis

Heterogeneous Volumes

This feature enables path-traced volume rendering of both VDB files (internally converted to NanoVDB, a faster and more compact GPU-friendly volume representation) and procedural MDL based volumes. VDB files can either contain a SDF (signed distance field/level set) or density volume. Currently, the VDB volume material can only be applied to a cube mesh, while procedural volume materials can be applied to any kind of mesh (cube, sphere, torus, etc). Volumes can also overlap with other volumes. The maximum number of overlaps between the volumes is currently limited to four.

How to create a VDB volume object

• Create a cube mesh

• In the cube’s Property tab, check isVolume

• Assign VDBTestMaterial.mdl to the cube

• In the Property tab of the VDBTestMaterial, assign a VDB file to the volume_density_texture

How to create a procedural volume object

• Create a cube mesh

• In the cube’s Property tab, check isVolume

• Assign either perlinNoise.mdl or worleyNoise.mdl to the cube

Setting	Effect
Heterogeneous Volumes	The number of bounces is controlled by Max Heterogeneous Volume Scattering Bounces (under the Path-Tracing section in Path-Traced Mode Settings). • When set to 1: perform single scattering. Fast, suitable for lowly scattering volumes like fog. • When set to a value greater than 1: perform multi-scattering. Slower, suitable for highly scattering volumes like clouds. Important: Make sure to increase the number of bounces to avoid darkening artifacts.
Transmittance Method	Choose between Biased Ray Marching, Ratio Tracking or Brute-Force Ray Marching. Biased ray marching is the ideal option in all cases.
Max Collision Count	Maximum delta tracking iterations. Increase to more than 32 for highly scattering volumes like clouds. Important: if set too low, parts of the volume will disappear.
Max Light Collision Count	Maximum ratio tracking iterations. Increase to more than 32 for highly scattering volumes like clouds. Important: if set too low, parts of the volume will disappear.
Max Density	Upper bound of the density of the volume (called Global Majorant in volume rendering). Important: if set too low, the volume will appear overly transparent.
Fast VDB	Accelerates volume rendering of VDB files by 3-6x at the same accuracy. This setting does not work with MDL based volumes.

Multi-GPU

Setting	Effect
Multi-GPU	Enables the use of multiple GPUs in path-traced mode (when these are available and enabled at startup) Multi-GPU must be enabled at startup by passing adding –/renderer/multiGpu/enabled=true to the command line
GPU 0 Weight	The amount of total Path-Tracing work (between 0 and 1) to be performed by the first GPU in a Multi-GPU configuration. A value of 1 means the first GPU will perform the same amount of work assigned to any other GPU.
Compress Radiance	Enables lossy compression of per-pixel output radiance values
Compress Albedo	Enables lossy compression of per-pixel output albedo values (needed by OptiX denoiser)
Compress Normals	Enables lossy compression of per-pixel output normal values (needed by OptiX denoiser)