--- title: "Global Illumination" canonical: "https://documentation.chaos.com/space/VRHINO/116130551/Global%20Illumination" format: markdown --- 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](https://docs-chaos.atlassian.net/wiki/spaces/VRHINO/pages/116131512) – The default engine for Primary Rays. It can be used for Secondary Rays as well. - [DEPRECATED][Irradiance Map Settings](https://docs-chaos.atlassian.net/wiki/spaces/VRHINO/pages/116130465) – This option is deprecated. An alternate engine for Primary Rays only. - [Light Cache Settings](https://docs-chaos.atlassian.net/wiki/spaces/VRHINO/pages/116132100) – The default engine for Secondary Rays. It can be used for Primary Rays as well. > ℹ️ V-Ray GPU always works with Brute Force as Primary rays engine. > ℹ️ The settings in some of the rollouts are organized in *Basic* and *Advanced* mode. You can switch the mode from the toggle button (> Macro (inline-media-image) > ℹ️ > ℹ️ ) located next to the rollout title or globally from the [Configuration](https://docs-chaos.atlassian.net/wiki/spaces/VRHINO/pages/116130562) rollout. ## **UI Path** --- ||V-Ray Asset Editor||** **>**  Settings** > **Global Illumination** ## **Global Illumination** --- ## **Light Cache/Brute Force** --- ## **Caustics** --- V-Ray supports the rendering of caustics effects by using one of the following techniques: photon mapping or progressive. The new **Progressive **caustics solver uses advanced sampling techniques, and is able to trace as many photons as required without suffering the memory constraints of traditional Photon Mapping techniques. It is loosely based on two papers: one on [Progressive Photon Mapping from Knaus and Zwicker](http://www.cs.jhu.edu/~misha/ReadingSeminar/Papers/Knaus11.pdf), and another on [Metropolis-guided caustics tracing from Šik and Krivánek](https://cgg.mff.cuni.cz/~jaroslav/papers/2019-corona-caustics/2019-sik-corona-caustics-paper.pdf). The other method, **Photon Mapping**, is a two-pass technique. The first pass consists of shooting light particles (photons) from the light sources in the scene, tracing them as they bounce around the scene, and recording the places where the photons hit the object surfaces. The second pass is the final rendering, which is when the caustics are calculated by using density estimation techniques on the photon hits stored during the first pass. > ℹ️ When using Interactive rendering, only Progressive Caustics are supported! If Photon Map method is selected, V-Ray silently falls back to Progressive method. > Macro (anchor) --- ### **Example: Progressive Caustics - Caustic Subdivs** (Caustic Subdivs parameter of the Lights' Caustic Photon option) Multiplier = 20; Search Distance = 100 --- ### **Photon Map Caustics** --- > Macro (anchor) --- ### **Example: Photon Map Caustics - Caustic Subdivs** **(Caustic Subdivs parameter of the Lights' Caustic Photon option)** Multiplier = 20; Search Distance Units = World; Search Distance = 0.5; Max Photons = 5000; Max Density = 0 --- ## **GI Caustics**  --- ## **Ambient Occlusion** --- --- > Macro (anchor) ### **Example: Ambient Occlusion** ** ** Note: the scene in this example is from Evermotion. ( [http://www.evermotion.org/](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. ## **Notes** --- - Since 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. ### Progressive Caustics Advantages - they require nearly no setup; - each cast photon is more useful than those in traditional Photon Mapping; - the number of photons castable is only limited by time, not memory; - they can resolve tiny caustic details, compared to the scene size; - they can resolve caustic details also when a camera is very zoomed in on them; - statistics about the photon tracing can be found in the VFB2 stats panel; ### Progressive Caustics Limitations - they require the progressive image sampler; - the image sampler often requires Min. subdivs values much higher than 1; - it's non-deterministic, meaning that there could be somewhat unpredictable render times, and also tiny differences in the visual results when rendering the same frame twice; - currently doesn't work with distributed rendering; - currently not supported by the GPU engine; - Depending on the scene, the performance might not scale linearly with the number of threads/cores, resulting in inefficient CPU utilization.