This is a master control for enabling global illumination.
The Global Illumination (GI) system lets you use two separate algorithms to calculate indirect lighting.
For example, you can calculate multiple light bounces with a fast algorithm like Path Tracer, and still calculate the final bounce with Final Gather to get a fast, high quality global illumination render. Both subsystems have individual control of Intensity and Saturation to boost the effects if necessary.
You can also set None for both Primary GI and Secondary GI. For Secondary GI, use None when you don’t need deeper indirect light or if you have a Primary GI that cannot use Secondary GI. Use None for primary global illumination when baking advanced passes that perform their own gather (such as Radiosity Normal Map when not using radiance cache, and the Lua pass). When these passes perform their own gather, only the Secondary GI is sampled, making any primary global illumination useless.
Select from the following algorithms:
This is a brute force GI method that calculates GI by sending rays in a hemisphere around the shading points. No caching is used so a new calculation is done for each shading point. An importance sampling method is used for secondary bounces, so a high number of bounces can be used without exploding the render time. The Monte Carlo method is unbiased and can be used for reference images when used as Primary GI. It can also be used as Secondary GI together with Final Gather to produce a multi-bounce high quality result without light leakage.
The Path Tracer algorithm calculates indirect lighting by tracing a (high) number of rays from the camera into the scene. These rays are bounced and traced further into the scene, depending on the properties of the surfaces they hit. Surfaces with a high diffuse reflectance will have a higher probability to continue the ray paths, hence giving more color bleeding to other surfaces. The path is only terminated when the probability for absorption is high enough.
Illumination from the ray bounces are stored at selected points in the scene, resulting in a set of cache points. A parameter, Cache Point Spacing, is used to set the distance between the cached points. A smaller distance will generate more cache points, and enable better capturing of details, but also higher memory usage and longer rendering time.
Once the pre-render pass completes, the path tracer cache holds an approximation of the indirect light. The quality of the solution depends on the number of paths used and the density of the cache. If the path tracer solution is used as Secondary GI, with Final Gather or Radiance Cache as Primary GI, the settings can be set quite low and still produce good quality.
The cache points can be saved to a map file and reused for successive renderings. Note that the file option Reuse and Refine will load the map from file and then refine the solution by adding the paths from a new pre-render pass to the cache. This improves the solution with each successive each rendering.
Master control for enabling caustics, using caustics photon mapping.
Scales the intensity of the first GI bounce.
Scales the saturation of the first GI bounce.
Scales the intensity of secondary GI bounces.
Scales the saturation of secondary GI bounces.
Scales the intensity of the caustics photon map.
Scales the saturation of the caustics photon map.
A gain for boosting the diffuse material components when used by GI. Can be used to adjust the amount of indirect diffuse lighting. For example, a scene with very dark textures will not get much indirect lighting, but when boosting all diffuse components the indirect effects are increased.
Scales the specular material components when used by GI. Can be used to adjust the amount of indirect lighting from specular effects.
Scales the emissive material components when used by GI. Can be used to adjust the amount of indirect lighting from emissive materials.
Controls whether to clamp materials to preserve physical correctness when used by global illumination. Select from the following options:
Disables material clamping.
Clamp each R, G and B component separately.
Clamp the intensity (HSV Value).
Selects what caching method to use for final gathering. Select from the following options:
Disables caching and performs a new final gathering for every shading point. Gives very accurate results but long render times. Use (for example) for reference images.
(Default.) Caches the irradiance at selected points in the scene and uses interpolation in between the points.
Caches radiance SH functions at selected points in the scene and uses interpolation in between the points. The radiance cache is useful in some advanced baking passes (such as Radiosity Normal Maps), when directional indirect lighting is needed.
Sets the maximum number of rays to use for each final gather sample point. A higher number gives higher quality, but longer rendering time.
Sets the number of indirect light bounces calculated by final gather. A value higher than 1 will produce more global illumination effects, but note that it can be quite slow since the number of rays will increase exponentially with the depth. It’s often better to use a fast method for secondary GI. If a secondary GI is used the number of set final gather bounces will be calculated first, before the secondary GI is called. In most cases, set to 1 when using a secondary GI.
Controls how sensitive the final gather should be for contrast differences between the points during precalculation. If the contrast difference is above this threshold for neighbouring points, more points will be created in that area. This tells the algorithm to place points where they are really needed, e.g. at shadow boundaries or in areas where the indirect light changes quickly. Hence this threshold controls the number of points created in the scene adaptively. Note that if a low number of final gather rays are used, the points will have high variance and hence a high contrast difference, so in that case you might need to increase the contrast threshold to prevent points from clumping together.
Sets the number of final gather points to interpolate between. A higher value will give a smoother result, but can also smooth out details. If light leaks through walls as this value increases, checking the sample visibility can solve the problem. See Check Sample Visibility below.
Turn this on to visualize the final gather prepass. Using Preview Calculation Pass enables a quick preview of the final image lighting, reducing lighting setup time.
Sets the minimum number of points that should be used when estimating final gather in the precalculation pass. The impact is that a higher value will create more points all over the scene. The default value 15 rarely needs to be adjusted.
Controls how sensitive the final gather should be for differences in the points normals. A lower value will give more points in areas of high curvature.
Controls how the irradiance gradient is used in the interpolation. Each point stores its irradiance gradient which can be used to improve the interpolation. However in some situations using the gradient can result in white ”halos” and other artifacts. This threshold can be used to reduce those artifacts.
The max distance a ray can be traced before it’s considered to be a “miss”. This can improve performance in very large scenes. If the value is set to 0.0 the entire scene is used. The distance is measured in Maya units.
When on, final gather also caches lighting from light sources. This increases performance since fewer direct light calculations are needed. It gives an approximate result, and hence can affect the quality of the lighting. For instance indirect light bounces from specular highlights might be lost. However this caching is only done for depths higher than 1, so the quality of direct light and shadows in the light map will not be reduced.
Turn this on to clamp the sampled values to [0, 1]. This will reduce low frequency noise when Final Gather is used together with other Global Illumination algorithms.
Turn this on to reduce light leakage through walls. When points are collected to interpolate between, some of them can be located on the other side of geometry. As a result light will bleed through the geometry. So to prevent this Turtle can reject points that are not visible.
This setting can be used to reduce light leakage through walls when using final gather as primary GI and photon mapping or path tracing as secondary GI. Leakage, which can happen when e.g. the path tracer filters in values on the other side of a wall, is reduced by using final gather as a secondary GI fallback when sampling close to walls or corners. When this is enabled a final gather depth of 3 will be used automatically, but the higher depths will only be used close to walls or corners. Note that this is only useable when photon mapping or path tracing is used as secondary GI.
Controls how far away from walls the final gather will be called again, instead of the secondary GI. If 0.0 is used a value will be calculated by Turtle depending on the secondary GI used. The calculated value is printed in the output window. If you still get leakage you can adjust this by manually typing in a higher value.
Controls usage of final gather map files. By saving the solution to a file, it can be reused for successive renderings. The file will be placed under turtle/fgMaps in the current project directory. Note that if lights or geometry are moved, recalculation is necessary.
Disables file usage.
Creates a new map file, overwriting any existing file.
Loads the map from a previously created file.
Loads the map from a file, but also writes back any new samples created during rendering.
Same as Reuse and append, but only the FG pre-pass is rendered. This can be used to generate an FG Map file for an animation sequence. First render the animation in this mode, creating the map file, then switch to Reuse before final rendering of the animation. Note that the animation frame step can be set higher than 1 during the precalculation to save time. For example, rendering every other frame, or even as sparse as every 10th frame.
Sets the name of the cache map file. The map file is saved in turtle/ptMaps in the current project directory.
If enabled the cache points saved to file are displayed in the viewport after the rendering.
Enables the older final gather method. With this method points are placed according to the geometry in the scene. More samples are placed near walls and corners of the geometry. The contrast difference of the samples are not considered.
Controls the sample point density. Higher accuracy generates more points and a better result at the expense of longer rendering time.
Applies a filter that reduces noise in the final gather solution. This is much faster than increasing accuracy or sending more rays. 1.0 is the default value. Values below 1.0 gives a sharper and noisier look. Values above 1.0 gives a smoother look with less details preserved.
When enabled more points are created in corners of the geometry, which can reduce artifacts. However don’t enable this unless you need to, because it increases render time.
Controls a scaling of Final Gather with Ambient Occlusion which can be used to boost shadowing and get more contrast in your lighting. The value controls how much Ambient Occlusion to blend into the Final Gather solution.
Max distance for occlusion. Beyond this distance a ray is considered to be unoccluded. Can be used to avoid full occlusion for closed scenes.
Can be used to adjust the contrast for ambient occlusion. Increase this value to make bright surfaces brighter and dark surfaces darker.
A scaling of the occlusion values. Can be used to increase or decrease the shadowing effect.
When on, a single Ambient Occlusion pass will be rendered, to visualize the AO effect. All other render passes are ignored. This can be useful while tuning your AO settings.
The start distance in world units.
The end distance in world units.
Controls the rate by which lighting falls off by distance. The exponent controls the shape of the function that goes from full intensity (at Attenuation Start) to zero intensity (at Attenuation Stop).
Sets the number of paths that are traced for each sample element (pixel, texel or vertex). For preview renderings, you can use a low value like 0.5 or 0.1, which means that half of the pixels or 1/10 of the pixels will generate a path. For production renderings you can use values above 1.0 if needed to get good quality.
Sets the average number of bounces in the Path Tracer solution. The maximum depth is 40. A lower Depth will result in a faster but noisier solution, but the overall intensities will be the same. How far light actually bounces is much dependent on your materials, brighter materials lets light spread further than dark materials.
Sets the maximum distance between the points in the path tracer cache. If set to 0.0 a value will be calculated automatically based on the size of the scene. The automatic value will be printed out during rendering, which is a good starting value if the point spacing needs to be adjusted.
Selects the filter to use when querying the cache during rendering. None will return the closest cache point (unfiltered).
Sets the size of the filter as a multiplier of the Cache Point Spacing value. For example, a value of 3.0 uses a filter that is three times larger then the cache point spacing. If this value is below 1.0 there is no guarantee that any cache point is found. If no cache point is found the Default Color will be returned instead for that query.
Prefilters the cache points before the final pass starts. This can increase the performance using the final render pass and is especially useful when Check Sample Visibility is enabled, or the filter kernel is large.
If enabled the pre-render pass is visible in the render view.
When on, final gather also caches lighting from light sources. This increases performance since fewer direct light calculations are needed. It gives an approximate result, and hence can affect the quality of the lighting. For instance indirect light bounces from specular highlights might be lost. However this caching is only done for depths higher than 1, so the quality of direct light and shadows in the light map will not be reduced.
Turn this on to reduce light leakage through walls. When points are collected to interpolate between, some of them can be located on the other side of geometry. As a result light will bleed through the geometry. So to prevent this Turtle can reject points that are not visible.
The Path Tracer needs to clamp the Maya materials so that they act in a physically accurate way. The Conservative Energy Limit parameter lets you set how tight the clamp is, where 1.0 would mean that a material is allowed to be exactly on the border of being non-physical. The default is 0.95, which means that the material is at most 5% below the critical limit.
Sets the color to be returned if no valid cache point is found during a cache query. If no points are found, the Filter Size needs to be increased. By setting the color to bright red or green, for example, you can easily see if a larger Filter Size is needed.
Selects how the cache points are saved or loaded from file. Overwrite will create a new map file. Reuse will load the cache points from the map file and skip the pre-render pass. Reuse and Refine will load the cache points from file but refine the solution by running the pre-render pass again.
Sets the name of the cache map file. The map file is saved in turtle/ptMaps in the current project directory.
If enabled the cache points saved to file will be displayed in Maya’s model view after the rendering.
Sets the number of rays to use for each calculation. A higher number gives higher quality, but longer rendering time.
Sets the average number of indirect light bounces calculated by Monte Carlo. A lower number means a noisier but faster solution, although the overall intensities will be the same.
The maximum distance a ray can be traced before it’s considered to be a “miss”. This can improve performance in very large scenes. If the value is set to 0.0 the entire scene will be used. The distance is measured in Maya units.
Sets the number of photons to use when calculating global illumination effects. A higher number gives higher quality but takes a longer time to calculate.
Sets the maximum search radius to use when searching for photons during lighting calculations for global illumination effects. If the Photon Radius is set to r, photons within a sphere of radius r around the sample point will be used to calculate the light. If the Photon Radius is set to 0.0 a value will be calculated automatically based on the size of the scene. The automatic value will be printed out during rendering, which is a good starting value if the point spacing needs to be adjusted.
When enabled, lighting from light sources is cached.
Sets the maximum number of bounces a global photon can take before it is absorbed.
When set to Specified the user can specify a minimum number of bounces a global photon must take before it is stored in the photon map. This can be used to alter the default global photon behavior, which is to store all photons when final gather is used and store all secondary photons when final gather is not used.
Sets the minimum number of bounces a global photon must take before it can be stored in the photon map.
Selects which algorithm to use when calculating global illumination effects. Standard Photon Mapping is more accurate but Grid Based Photon Mapping is much faster.
Sets the number of grid cells when Grid Based Photon Mapping is used. A higher number gives higher accuracy but longer rendering time. If the scene is very complex, a higher value may be necessary.
When enabled, the irradiance will be precalculated at the photon positions before the rendering starts. This gives a much faster rendering at the cost of lower accuracy. If standard photon mapping is used with final gather, it is recommended to enable this feature.
Controls how often the precalculation is applied in the photon map. If set to 1 precalculation will be done at all photon positions, if set to 2 at half of the positions, if set to 4 at one quarter of the position, etc. Hence a higher value gives faster rendering but less accuracy.
Enables usage of photon map files. By saving the photon map to a file, it can be reused in successive renderings. The file will be placed under turtle/photonMaps in the current project directory. Note that if lights or geometry is moved, recalculation is necessary. Off disables file usage. Overwrite creates a new photon map file, overwriting any existing file. Reuse loads the photon map from a previously created file.
Sets the filename of the global photon map file.
Visualize the stored photons as a point cloud in the viewport. You can change point size and color in the attributes of the generated point cloud.
Number of photons to be emitted into the scene.
Sets the number of photons to use when calculating global illumination effects. A higher number gives higher quality but takes a longer time to calculate.
The preview of the Dynamic Photon Map is only meant to be used to fine tune the intensity of the indirect dynamic light for a baking pass, and will not produce any quality results. In a typical case, you turn off any other lights in the scene, giving you a rough picture of the influence you’ll get from the photon map (e.g. when baking color bleeding to a PTM). The Dynamic Photon Map contains photons from any possible direction; the Preview Light Direction specifies one such direction for evaluation of the map.
Sets the maximum search radius to use when searching for photons during lighting calculations for global illumination effects. If the Photon Radius is set to r, photons within a sphere of radius r around the sample point will be used to calculate the light. If the radius is set to 0.0, an automatic value will be used.
Sets the minimum number of bounces a global photon must take before it can be stored in the photon map.
Number of bands to use for the spherical harmonics function in each grid cell. A higher number of bands will allow for more high frequent illumination data.
Incoming photons are stored on their emit direction. This setting determines the number of buckets (each associated with a direction) that will be used for photon collection. Again, a higher number allow for information of higher frequency.
Sets the number of grid cells when for the Dynamic Photon Map data structure. A higher number gives higher accuracy but longer rendering time. If the scene is very complex, a higher value may be necessary.
Enables usage of photon map files. By saving the photon map to a file, it can be reused in successive renderings. The file will be placed under turtle/photonMaps in the current project directory. Note that if lights or geometry is moved, recalculation is necessary. Off disables file usage. Overwrite creates a new photon map file, overwriting any existing file. Reuse loads the photon map from a previously created file.
Sets the filename of the dynamic photon map file.
Caustics effects are handled with a special photon map in Turtle. You must explicitly emit caustics photons from light sources.
Influences the number of photons to use when calculating caustics effects, a higher number take more photons into account. Default value is 1.0.
Sets the maximum search radius to use when searching for photons during lighting calculations for caustics effects. If the Photon Radius is set to r, photons within a sphere of radius r around the sample point will be used to calculate the light. The radius is given in Maya units.
Sets the maximum number of bounces a caustics photon can take before it is absorbed.
Enables usage of photon map files. By saving the photon map to a file, it can be reused in successive renderings. The file will be placed under turtle/photonMaps in the current project directory. Note that if lights or geometry is moved, recalculation is necessary.
Sets the filename of the caustics photon map file.
Visualize the stored caustic photons as a point cloud in the viewport. You can change point size and color in the attributes of the generated point cloud.
Here you can set which GI solution each ray type should see. This can be used for optimization on ray type. For instance Glossy reflections generally does well with using the photon map directly instead of final gather.
When enabling this, the rendering terminates after the GI prepass is done. This is useful if you want to distribute renderings between different computers. Typically you run through an animation perhaps, each 10th frame, on one computer with ”Reuse and append” file mode for the GI. You can then distribute this GI solution to a cluster of render nodes to avoid flickering GI in the animation. It can also be used to avoid seams between tiles when using many computers to render one frame.