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Kernels

There are four major rendering kernels in OctaneRender™: Direct Lighting, Path Tracing, PMC and Deep Channel.

Direct Lighting

Direct Lighting is used for faster preview rendering. Direct Lighting is not unbiased but is useful when creating quick animations or renders.

• Maximum Samples: This sets the maximum number of samples per pixel before the ren­dering process stops. The higher the number of samples per pixel, the cleaner the render. For quick animations and scenes with predomi­nantly direct lighting, a low amount of samples (500-1000) may suf­fice. In scenes with lots of indi­rect lighting and mesh lights, a few thousand samples may be required to obtain a clean render.
• GI Mode: There are five different Global Illumination modes in the Direct Lighting Kernel:
• None: Only direct lighting from the sun or area lights is included. Shadowed areas receive no contribution and will be black.
• Ambient: Use a simple ambient colour from the environment above.
• Sample Environment: Use a simple ambient colour from the environment/horizon. Together with ambient and none, these modes are all very fast, as no Monte Carlo sampling is required. These give a very unrealistic, classic z-buffer/whitted raytracing style look, but are very fast, and very handy for interactive tuning of complex scenes or on slow hardware.
• Ambient Occlusion: Standard ambient occlusion. This mode can often provide re­alistic images but offers no color bleeding.
• DiffuseAmount of diffusion, or the reflection of light photons at different angles from an uneven or granular surface. Used for dull, non-reflecting materials or mesh emitters.: Indirect diffuse, with a configuration to set the number of in­direct diffuse bounces to include. This gives a GI quality that is in between Ambient Occlusion and pathtracing, without caustics and a decent realistic quality (better than AO), but much faster than pathtracing/PMC. It is very good for quick finals and animations. It is similar in some ways to ‘bruteforce’ indirect GI in other engines.
• Diffuse Depth: Gives the maximum number of diffuse reflections if GI Mode is set to Diffuse (4)
• 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 can be refracted before dying. Higher numbers mean higher render times but more color bleeding and more details in transparent materials. Low numbers can 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 can be reflected before dying. Higher numbers mean higher render time. Low numbers under “4” can introduce artifacts, or turn some reflections into pure black. You should setup this setting based on the complexity of the scene you are working on, and especially based on how many reflective parallel surfaces you have.
• AO Distance: The distance of the ambient occlusion in units. Always check if the amount is right related to your model scale. For example you don’t need an amount of “3” units if your object is a small toy. But if your model is a house or something large, you can increase the value. The more you increase the value the darker your render will be.
• Ray Epsilon is the distance to offset new rays so they don’t intersect with the originating geometry. If the scale of your scene is too large, precision artifacts in the form of concentric circles may appear. In that case, increasing the ray epsilon can make these artifacts disappear.
• Filter Size: This sets the pixel size for fil­tering the render. This can im­prove aliasing artifacts in the render. Noise can also be re­duced this way, but if the filter is set too high, the image can become blurry.
• Alpha Shadows: This setting allows any object with transparency (specular materials, materials with opacity settings and alpha channels) to cast a proper shadow instead of behaving as a solid object.
• Alpha ChannelA greyscale image used to determine which areas of a texture map are opaque and which areas are transparent.: This option removes the background and renders it as transparant (zero alpha). This can be useful if the user wants to composite the render over another image and does not want the background to be present.
• Path Term Power: this is the path termination strategy. The default setting should be good in most cases. If some dark patches stay too noisy too long, you can lower the value, which will slow down rendering, but cause Octane to spend more time on those areas.
• Coherent Ratio: This feature increases the render speed, but causes some “flickering” during the first samples/pixel and should be mainly used for the final rendering and if only if you plan to render 500 samples/pixel or more. This feature is always disabled in the IPRProvides artists a quick preview of the image prior to the final render, and efficiently allows for adjusting some elements in the scene such as lights, shaders and textures interactively. An IPR image contains shading and lighting data including some for visibility, in addition to the software render. window. The percent parameter allows you to blend between non-coherent rendering (0%) and “super-coherent” rendering (100%). Please be aware that for values above 0.4 you will usually need a few thousand samples per pixel to get rid of visible artifacts and values above 0.5 hardly ever make any sense.
• Static Noise: When enabled, the noise is static, i.e. doesn’t change between frames.

Path Tracing

Path Tracing is best used for realistic results (together with PMC). The render times are higher than Direct Light­ing but the results can be photorealistic. It can have some difficulties with small light sources and proper caustics (for which pmc is better suited).

• Maximum Samples: This sets the maximum number of samples per pixel before the rendering process stops. The higher the number of samples per pixel, the cleaner the render. There is no rule as to how many samples per pixel are required for a good render.
• Maximum Diffuse and Glossy Depth: The maximum number of times a ray can bounce/re­flect/refract in a surface. Higher amounts mean also higher render time but more realistic results. For outdoor renders a good setting is around 4 maxdepth. For light­ing interior with natural light (the sun and the sky) you will need higher settings such as 8 or higher to allow enough light to bounce around in the scene. While high values are possible, in reality rays will not usually go beyond 16 ray depth.
• Ray Epsilon: The ray epsilon is the distance to offset new rays so they don’t intersect with the originating geometry. If the scale of your scene is too large, pre­cision artifacts in the form of concentric circles may appear. In that case, increasing the ray epsilon can make these artifacts disappear.
• Maximum Samples: This sets the maximum number of samples per pixel before the ren­dering process stops. The higher the number of samples per pixel, the cleaner the render. There is no rule as to how many samples per pixel are required for a good render.
• Filter Size: This sets the pixel size for filter for the render. This can improve alias­ing artifacts in the render. If the filter is set too high, the image can become blurry.
• Alpha Shadows: This setting allows any object with transparency (specular materials, materials with opacity settings and alpha channels) to cast a proper shadow instead of behaving as a solid object.
• Alpha Channel: This option removes the background and renders it as transparant (zero alpha). This can be useful if the user wants to composite the render over another image and does not want the background to be present.
• Caustic Blur: This is used to approximate caustics on rough surfaces and increase or decrease the sharpness of caustic noise. A zero value provides the sharpest caustics and increasing this value increases the blur­ing effect to make caustics appear softer.
• GI Clamp: It clamps the contribution for each path to the specified value. By reducing the “GI clamp” value, you can reduce the amount of fireflies caused by sparse but very strongly contributing paths. Reducing this value reduces noise by removing energy. On the other hand, “caustic blur” reduces noise by blurring caustics, but conserves energy.
• Path Term Power: this is the path termination strategy. The default setting should be good in most cases. If some dark patches stay too noisy too long, you can lower the value, which will slow down rendering, but cause Octane to spend more time on those areas.
• Coherent Ratio: This feature increases the render speed, but causes some “flickering” during the first samples/pixel and should be mainly used for the final rendering and if only if you plan to render 500 samples/pixel or more. This feature is always disabled in the IPR window. The percent parameter allows you to blend between non-coherent rendering (0%) and “super-coherent” rendering (100%). Please be aware that for values above 0.4 you will usually need a few thousand samples per pixel to get rid of visible artifacts and values above 0.5 hardly ever make any sense.
• Static Noise: When enabled, the noise is static, i.e. doesn’t change between frames.

PMC

PMC is a custom mutating unbiased kernel written for GPUs. It allows for com­plex caustics and lighting to be resolved.

• Maximum Samples: This sets the maximum number of samples per pixel before the ren­dering process stops. The higher the number of samples per pixel, the cleaner the render.
• Maximum Diffuse and Glossy Depth: The maximum number of times a ray can bounce/ reflect/refract in a sur­face. Higher amounts mean also higher render time but more realistic results. For outdoor renders a good setting is around 4 maxdepth. For lighting in­terior with natural light (the sun and the sky) you will need higher settings such as 8 or higher. While high values are possible, in reality rays will not usually go beyond 16 ray depth.
• Ray Epsilon: The ray epsilon is the distance to offset new rays so they don’t in­tersect with the originating geometry. This value should be left as the default.
• Filter Size: This sets the pixel size for filter for the render. This can improve alias­ing artifacts in the render. If the filter is set too high, the image can become blurry.
• Alpha Shadows: If alpha maps are used in the scene, this setting controls whether the shadows will be calculated from the mesh geometry or from the alpha map.
• Alpha Channel: This option removes the background and renders it as transparant (zero alpha). This can be useful if the user wants to composite the render over another image and does not want the background to be present.
• Caustic Blur: This is used to approximate caustics on rough surfaces and increase or decrease the sharpness of caustic noise. A zero value provides the sharpest caustics and increasing this value increases the blur­ing effect to make caustics appear softer.
• GI Clamp: It clamps the contribution for each path to the specified value. By reducing the “GI clamp” value, you can reduce the amount of fireflies caused by sparse but very strongly contributing paths. Reducing this value reduces noise by removing energy. On the other hand, “caustic blur” reduces noise by blurring caustics, but conserves energy.
• Exploration Strength: This specifies how long the kernel investigates good paths before it tries to find a new path. L ow values can create a noisy image while larger values can create a splotchy image.
• Direct Light Importance: The direct light importance makes the kernel focus more on paths with indirect light. For example, imagine sunlight through a window that creates a bright spot on the floor. If the direct light importance is 1, the kernel would sample this area a lot, although it becomes clean very quickly. If the direct light importance is reduced, the kernel reduces its efforts to sample that area and focuses more on more tricky areas that are harded to render.
• Max Rejects: This can control the “bias” of the render. By reducing the value, the result will be more biased, but the render time will be shorter.
• Parallelism (parallelism): This is used to reduce the number of samples that are investigated in parallel to make caustics appear earlier at the expense of some performance.
• Path Term Power: this is the path termination strategy. The default setting should be good in most cases. If some dark patches stay too noisy too long, you can lower the value, which will slow down rendering, but cause Octane to spend more time on those areas.

InfoChannel Kernel

The Info_channel_ker­nel creates false-color images of the scene, containing various types of information about the scene. In scenes where the environment is vis­ible you should enable the alpha channel.

The following settings are available:

• Geometric normals: the vectors perpendicular to the triangle faces of the mesh.
• Shading normals: the interpolated normals used for shading. This does not take into account the bump map of the object. For objects without smoothing this is identical to the geometric normals.
• Position: The position of the first intersection point.
• Z-depth: The distance between the intersection point and the camera, measured parallel to the view vector.
• MaterialThe representation of the surface or volume properties of an object. ID: Every material pin is represented as a separate color.
• Texture Coordinates: shows the UV coordinates for the surface (this is only useful for export script writers).
• Wireframe: Shows the mesh as represented by edges, vertices and surfaces.
• Interpolated Vertex Normals: Similar to shading normals preset but also strictly calculates the shading based on vertex normals provided by actual data in the mesh. This makes flawed.
• Object ID: Every object is represented as a separate color.
• Ambient Occlusion (AO): Render an ambient occlusion pass
• Motion Vectors

For display these values are scaled to get values approximately be­tween 0 and 1. All tone mapping settings except for min_display_ samples and gamma are ignored. Exposure is enabled for Z-depth, and will indicate the value which gets mapped to white. To save these channels you should use untonemapped EXRAlso known as OpenEXR. This image file format was developed by Industrial Light & Magic and provides a High Dynamic Range image capable of storing deep image data on a frame-by-frame basis..

• Maximum Samples: This sets the maximum number of samples per pixel before the ren­dering process stops. The higher the number of samples per pixel, the cleaner the render. There is no rule as to how many samples per pixel are required for a good render.
• Filter Size: This sets the pixel size for filter for the render. This can improve alias­ing artifacts in the render. If the filter is set too high, the image can become blurry.
• Alpha Channel: This option removes the background and renders it as transparant (zero alpha). This can be useful if the user wants to composite the render over another image and does not want the background to be present.
• Maximum Z-DepthA measure of object distances from the camera typically represented as a grayscale image.: Gives the maximum z-depth that can be shown.
• Maximum UV value: Gives the maximum value that can be shown for the texture coordi­nates.
• AO distance: Used to specify distance of Ambient Occlusion.
• Ray Epsilon: The ray epsilon is the distance to offset new rays so they don’t in­tersect with the originating geometry. This value should be left as the default.
• Wireframe Backface Highlighting: Option to highlight backface in wireframe channel.
• Bump and Normal Mapping: Option to show or not show the bump and normal map.
• Distributed Ray Tracing: Enable the motion blur, DOFThe distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Although a lens can precisely focus at only one distance at a time, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions. source: wikipedia (https://en.wikipedia.org/wiki/Depth_of_field) and filtering while rendering the current image channel.
• Motion Max. Speed:
• AO alpha shadows: If enabled, opacity is now taken into account in the AO calculation.
• UV Set: Select the UV map rendered in the UV channel output.

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