This page gives an overview of the Global Illumination render element and explains how it is used in compositing.
The Global Illumination Render Element is a color image that stores indirect lighting information coming from reflected diffuse light in a scene ( without direct light and reflection contributions) when Indirect Illumination is enabled. This element may be used directly in compositing and adjusted for brightness and color to control the final image easily.
For even more control of indirect illumination without rerendering the scene, the Global Illumination render element may be re-assembled by multiplying the VRayRawGlobalIllumination Render Element by the Diffuse Filter Render Element:
VRayRawGlobalIllumination x VrayDiffuseFilter = VRayGlobalIllumination
Since V-Ray Next Update 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.
Previously this behavior depended on the sampling of the lights and not just on the type of the contribution. Some of the direct contributions that should be in the Lighting and Specular elements were written to the GI and Reflection elements instead. In both cases they compose back to Beauty correctly but the different types of contributions are now split between the elements more consistently.
This change makes the elements more consistent but it's also needed for preventing artifacts in these elements with the adaptive dome light (and possibly in the future with other adaptive lights).
The raw elements are affected only when the corresponding normal and filter elements are available, otherwise they're rendered as before. This is because the raw elements have to be derived internally from the corresponding normal elements in order to work with the consistent elements (f.e. VRayRawGlobalIllumination = VRayGlobalIllumination / DiffuseFilter).
There's an option to enable or disable the new behavior in the Global Switches rollout under the V-Ray tab in the Render Setup window. The consistent elements are automatically enabled when the scene contains an adaptive dome light so they don't have artifacts. They are also enabled by default for new scenes. For V-Ray GPU they are always enabled without an option to disable them.
||Render Setup window|| > Render Elements tab > Add button > VRayGlobalIllumination
This render element is enabled through the Render Elements tab of the Render Setup window in 3ds Max and displays its parameters in a rollout at the bottom of the window:
vrayVFB – Enables the render element inside the V-Ray frame buffer.
deep output – Specifies whether to include this render element in deep images.
color mapping – Applies the color mapping options specified in the Color mapping rollout of the V-Ray tab in the Render Setup window to this render element. This option is enabled by default.
multiplier – Can be used to amplify the element by a number value.
denoise – Specifies whether to denoise this render element
The Global Illumination Render Element is useful for changing the appearance of Indirect lighting after rending in a compositing or image editing software. Below are a couple of examples of its use.
Global Illumination Render Element
Original Beauty Composite
Tinted and Brightened GI