The Direct Light kernel is used for faster preview rendering. Direct Lighting is not unbiased and will not yield photorealistic results, but because of its speed, it is ideal for rendering animations or stills, depending on the project's demands. This Kernel has a series of sub-rollouts of attributes (figure 1).
Figure 1: The Direct Light settings in the Attribute Editor window
Max. Samples - Sets the maximum number of samples per pixel before the rendering process stops. Higher values result in cleaner renders.
GI Mode - There are three possible settings:
SpecularAmount of specular reflection, or the mirror-like reflection of light photons at the same angle. Used for transparent materials such as glass and water. Depth - Controls the number of times a ray refracts before dying. Higher numbers mean higher render times, but more color bleeding and more details in transparent materials. Low numbers introduce artifacts or turn some refractions into pure black.
GlossyThe measure of how well light is reflected from a surface in the specular direction, the amount and way in which the light is spread around the specular direction, and the change in specular reflection as the specular angle changes. Used for shiny materials such as plastics or metals. Depth - Controls the number of times a ray reflects before dying. Higher numbers mean higher render times. Values lower than 4 can introduce artifacts, or turn some reflections into pure black.
Diffuse Depth - Gives the maximum number of diffuse reflections if GI Mode is set to Diffuse.
Max Overlapping Volumes - Determines how much space to allocate for overlapping volumes. Ray marching is faster with low values but it can cause artifacts where many volumes intersect.
Ray Epsilon - The distance between the geometry and the light ray when calculating ray intersections for lighting and shadowing. Larger values push rays away from the geometry surface. Lower values are more accurate, but cause artifacts on large or distant objects. Ray Epsilon is similar to ray tracing bias in other rendering engines. Adjust Ray Epsilon to reduce artifacts in large-scale scenes.
Filter Size - Sets the filter size in terms of pixels. This improves aliasing artifacts in the render. However, if the filter is set too high, the image can become blurry.
AO Distance - The distance of the ambient occlusion shadowing spread in units. This setting provides realistic results, depending on the scale of the objects in the scene. Small values are more appropriate for small objects like toys, and larger values are more appropriate for something like a house.
AO Ambient Texture - Specifies an Ambient Occlusion texture, which is used for the AO calculation instead of the environment. If AO Ambient Texture is disabled, the environment is used instead. This gets rid of the blue tint on white walls caused by the blue sky (e.g., in Octane Sun Sky).
Alpha Shadows - This enables direct light through Opacity maps. If disabled, ray tracing is faster, but it renders incorrect shadows for alpha-mapped geometry or Specular materials with fake shadows enabled. Alpha Shadows allows any object with transparency (Specular materials, materials with Opacity settings, and Alpha Channels) to cast a shadow instead of behaving as a solid object.
Nested Dielectrics - If disabled, the surface IORs are not tracked and surface priorities are ignored.
Irradiance Mode - This renders the first surface as a white Diffuse material. Irradiance Mode is similar to Clay Mode, but it applies to just the first bounce. It disables the Bump channel and makes samples that are blocked by back faces transparent.
Max Subdivision Level - The maximum subdivision level that should be applied on the geometry in the scene. A value of 0 disables subdivision.
Alpha ChannelA greyscale image used to determine which areas of a texture map are opaque and which areas are transparent. - Removes background images or colors created by the SunSky environment node from the rendered image while not affecting any lighting cast by the environment. This is useful if the you want to composite the render over another image without the background being present. Objects appearing in the RGB channels have a bleeding edge, which appear as noise artifacts, but these edges are not included in the Alpha Channel itself.
Keep Environment - Used in conjunction with the Alpha Channel setting. It makes the background visible in the rendered image while also keeping the Alpha Channel.
Light linking provides a way to include and exclude illumination contributions of light sources on objects in a scene. The light IDs are set in Emitter nodes under the Emission rollout for the Diffuse MaterialThe representation of the surface or volume properties of an object., and this light ID corresponds to the Light IDs found here in the KernelSettings. Octane has eight Light IDs, and you can also choose whether to enable the sun and environment separately.
Path Termination Power - Provides a system to tweak samples per second vs. convergence (how fast noise vanishes). Higher values cause the kernels to keep paths shorter and spend less time on dark areas, which means they stay noisy longer, but it increases the samples per second. Lower values cause kernels to trace longer paths on average and spend more time on dark areas. In short, high values increases the render speed, but lead to more noise in dark areas.
Coherent Ratio - Increasing this value increases the render speed, but it introduces low-frequency noise or blotches. Eliminating the blotchy appearance requires a few hundred or even a few thousand samples per pixel, depending on the scene's contents.
Static Noise - Keeps noise patterns static between rendered frames in a sequence. The noise is static as long as the same GPUThe GPU is responsible for displaying graphical elements on a computer display. The GPU plays a key role in the Octane rendering process as the CUDA cores are utilized during the rendering process. architecture is used for rendering. Different architectures produce different numerical errors, which manifest as small differences in the noise pattern.
Parallel Samples - Controls how many samples Octane calculates in parallel. Smaller values require less memory to store the sample's state, but causes slower renders. High values require more memory, but reduce the render time. The change in performance depends on the scene and the GPU architecture.
Max Tile Samples - Controls the number of samples per pixel that Octane renders before storing the result in the render buffer. Higher values mean that results arrive less often in the film buffer.
Minimize Net Traffic - Distributes the same tile to the net render slaves until Octane reaches the maximum number of samples per pixel for that tile, and then it distributes the next tile to slaves. This option doesn't affect work done by local GPUs. A slave can merge all of its results into the same cached tile until the master switches to a different tile.
Enable Adaptive SamplingA method of sampling that determines if areas of a rendering require more sampling than other areas instead of sampling the entire rendering equally. - Enables adaptive sampling.
Noise Threshold - Specifies the smallest relative noise level. When the noise estimate of a pixel is less than this value, sampling switches off for this pixel. Good values are in the range of 0.01 - 0.03. The default is 0.02, which is pretty clean.
Min. Adaptive Samples - Specifies the minimum number of samples to calculate before adaptive sampling kicks in. A pixel's noise estimate has a large initial error. The higher you set the noise threshold, the higher you should also set this parameter to avoid artifacts.
Pixel Grouping - Specifies the number of pixels handled together. When all of the pixels in a group reach the noise level, sampling stops for all of these pixels.
Expected Exposure - This value should be close to the same value as the image's exposure, or 0 (the default value) to ignore these settings. Adaptive sampling uses this parameter to determine what pixels are bright and dark, which depends on the Octane Imager's exposure setting. If the value is not 0, adaptive sampling adjusts the noise estimate of the image's very dark areas. It also increases the Min. Adaptive Samples limit for very dark areas, because very dark areas tend to find irregular paths to light sources, resulting in over-optimistic noise estimates.
Controls the white light spectrum produced by spectral emitters (daylight, environment, black body).This determines the spectrum that will produce white (before white balance) in the final image.
Deep image rendering stores the Z-depth location of an object with samples of a rendered image. It works best in scenarios where traditional compositing techniques fail, such as compositions where masking out overlapping objects is too difficult, or scenes that render images images using depth-of-field or motion blur, or compositing footage in rendered volumes. Instead of having single RGBA values for a pixel, a deep image stores multiple RGBA channel values per pixel together with a front and back Z-depth (Z and ZBack channels, respectively). This combination (R, G, B, A, Z, ZBack) is called a deep sample.
Most major compositing applications now support deep image compositing. The disadvantage of deep image rendering is the large amounts of memory required to render and store deep images. The standard output format is OpenEXR.
Deep ImageRenders frames with multiple depth samples in addition to typical color and opacity channels. - Enables deep pixel image rendering for deep image compositing.
Maximum Depth Samples - When Deep Image Rendering is enabled, this sets the maximum number of depth samples per pixel.
Depth Tolerance - When Deep Image Rendering is enabled, Octane merges the depth samples whose relative depth difference falls below this value.
Toon Shadow Ambient - This is the ambient modifier of Toon Shadowing.