This page provides information on the Global Illumination settings in the Asset Editor.
Overview
Global illumination refers to lighting in a scene/environment that comes from light bouncing around and off objects (or the environment itself). Global Illumination (or GI) refers to the computation of this effect through computer graphics.
V-Ray implements several approaches (called engines) for computing indirect illumination with different trade-offs between quality and speed. Additional rollouts become available depending on the engine(s) specified for Primary and Secondary Rays:
- Brute Force Settings – The default engine for Primary Rays. It can be used for Secondary Rays as well.
- Irradiance Map Settings – An alternate engine for Primary Rays only.
- Light Cache Settings – The default engine for Secondary Rays. It can be used for Primary Rays as well.
V-Ray GPU always works with Brute Force as Primary rays engine.
The settings in some of the rollouts are organized in Basic and Advanced mode. You can switch the mode from the toggle button () located next to the rollout title or globally from the Configuration rollout.
UI Path
||V-Ray Asset Editor|| > Settings > Global Illumination
Global Illumination
Enabled – Turns indirect illumination on and off.
Primary Rays – Specifies the GI method to use for primary diffuse bounces.
Irradiance map – Causes V-Ray to use an irradiance map for primary diffuse bounces. See the Irradiance Map Settings section for more information.
Brute force – Specifies direct computation for primary diffuse bounces. See the Brute Force Settings section for more information.
Light cache – Specifies the light cache for primary diffuse bounces. See the Light Cache Settings section for more information.
Secondary Rays – Specifies the GI method to use for secondary diffuse bounces.
None – No secondary bounces are computed. Use this option to produce skylit images without indirect color bleeding.
Brute force – Specifies direct computation for secondary diffuse bounces. See the Brute Force Settings section for more information.
Light cache – Specifies the light cache for secondary diffuse bounces. See the Light Cache Settings section for more information.
Light Cache/Brute Force
The second rollout of the Global Illumination settings allows adjustment of the Secondary GI engine - either Brute Force or Light Cache. For more information on each, please refer to their respective page.
Light Cache as Secondary GI engine
Brute Force as Secondary GI engine
GI Caustics
Reflective Caustics – Allows indirect light to be reflected from specular objects like mirrors, etc. Note that this is not the same as Photon Mapped Caustics, which represent direct light being reflected by reflective surfaces.
Refractive Caustics – Allows indirect lighting to pass through a transparent objects like glass, etc. Note that this is not the same as Photon Mapped Caustics, which represent direct light going through transparent objects. You need refractive GI caustics to get skylight through windows, for example.
For accurate caustic calculations, disable the material refraction parameter Affect Shadows. Simultaneous usage of both Caustics and Affects Shadows can be used for artistic purposes but it will not produce a physically correct result.
Ambient Occlusion
These controls allow an ambient occlusion term to be added the global illumination solution.
Enabled – Turns ambient occlusion on or off.
Radius – Determines the amount of area (in Scene units) where the ambient occlusion effect is produced.
Occlusion Amount – Multiplies the amount of ambient occlusion. A value of 0.0 produces no ambient occlusion.
Example: Ambient Occlusion
Note: the scene in this example is from Evermotion. ( http://www.evermotion.org/)
This example demonstrates the effect of the global ambient occlusion options.
The first image to the right is rendered with the Light cache for both primary and secondary bounces, Fixed Filter type for the light cache, and Store direct light off. The second image in the center is rendered with the same light cache settings, but with global ambient occlusion enabled. The third image to the right is rendered without ambient occlusion, with Brute force GI engine for primary bounces, and the Light cache as a secondary engine with Nearest Filter type. The render times include the time for calculating the light cache. Note how ambient occlusion can produce a feeling of a more detailed image, even though the result is not entirely correct.
Ambient occlusion is off - lighting is good, but there is a lack of detail
Ambient occlusion is on - details are much more defined
Brute force GI, no ambient occlusion - details are fine, but render times is longer.
Photon Mapped Caustics
Photon Mapped Caustics – Enables or disables rendering of caustics.
Multiplier – Controls the strength of the caustics. This parameter is global and applies to all light sources that generate caustics. If different multipliers for the different light sources are desired, then use the local light settings. note that this multiplier is cumulative with the multipliers in the local light settings.
Search Distance – When V-Ray renders the caustics effect at a given surface point, it searches for a number of photons on that surface in the area surrounding the shaded point (search area). The search area in fact is a circle with center the original photon and its radius is equal to the Search distance value. Smaller values produce sharper, but perhaps more noisy caustics; larger values produce smoother, but blurrier caustics.
Max Photons – Specifies the maximum number of photons that is considered when rendering the caustics effect on a surface. Smaller values cause fewer photons to be used and the caustics are sharper but noisier. Larger values produce smoother but blurrier caustics. The special value of 0 means that V-Ray uses all the photons that it can find inside the search area.
Max Density – Limits the resolution (and thus the memory) of the caustics photon map. Whenever V-Ray needs to store a new photon in the caustics photon map, it first checks if there are any other photons within a distance specified by Max density. If there is already a suitable photon in the map, V-Ray just adds the energy of the new photon to the one in the map. Otherwise, V-Ray stores the new photon in the photon map. Using this options allows you to shoot many photons (and thus get smoother results) while keeping the size of the caustics photon map manageable.
Disk Caching rollout is available only in advanced mode of the Global Illumination rollout.
Mode – Controls the mode of the irradiance map:
New map – When enabled, a new photon map is generated. It overwrites any previous photon map left over from previous rendering.
From file – When enabled, V-Ray does not compute the photon map but loads it from a file. Press the Browse button on the right to specify the file name.
Keep File – When enabled V-Ray keeps the photon map in memory after the scene rendering has finished. When disabled, the map is deleted and the memory it took is freed. Enabling this option can be especially useful if you want to compute the photon map for a particular scene only once and then re-use it for further rendering.
Auto-Save File – When enabled, V-Ray automatically saves the caustics photon map to the provided file when rendering is completed. Specifies the file location where the caustics photon map is saved after rendering.
Caustics are not supported in VR Camera and Stereo Camera modes.
Photon mapped caustics are not available in V-Ray GPU.
Notes
- In V-Ray Next Update 1.1 some of the render elements are rendered differently than before. The Lighting render element now contains all direct diffuse illumination and the GI element contains all indirect diffuse illumination. Similarly, all direct reflections of lights now go to the Specular element and all indirect reflections go to the Reflection element.