The Irradiance MapВ method can only be selected as the EngineВ for Primary Bounces it is not available for Secondary Bounces. The diagram above shows the way the Irradiance Map is generated. During the actual rendering, V-Ray uses a sophisticated interpolation method to derive an approximation of the irradiance for all surfaces in the scene. If not, the indirect illumination for the current point is computed, and that point is stored in the Irradiance Map. Based on that information, V-Ray decides if the indirect illumination for the current point can be adequately interpolated from the points already in the Irradiance Map, or not. if there are any objects close by, how fast the indirect illumination is varying etc). From those already computed points, V-Ray can extract various information (i.e. When an object is hit during a GI pass, V-Ray looks into the Irradiance Map to see if there are any points similar in position and orientation to the current one. The Irradiance Map is in fact a collection of points in 3D space (a point cloud) along with the computed indirect illumination at those points. The idea is to start with a low resolution (say a quarter of the resolution of the final image) and work up to the final image resolution. This is done by rendering the image several times (each rendering is called a pass ) with the rendering resolution being doubled with each pass. The Irradiance Map is therefore built adaptively.

where objects are close to each other, or in places with sharp GI shadows), and less accurately in large, uniformly lit areas. Since not all parts of the scene have the same detail in indirect illumination, it makes sense to compute GI more accurately in the important parts (e.g. In V-Ray, the term irradiance map refers to a method of efficiently computing the diffuse surface irradiance for objects in the scene. In more simple terms, one can think of the diffuse surface irradiance as being the visible color of a surface, if we assume that its material is purely white and diffuse. The second restriction is that for diffuse surface irradiance (the total amount of light arriving at a given surface point) we can disregard the direction from which the light comes.

This is a natural restriction since we are usually interested in the illumination of objects in the scene, and objects are usually defined by their surfaces. The first is the restriction of looking only at surface irradiance, which is the irradiance arriving at points which lie on the surface of objects in the scene. However, there are two useful restrictions that can be made when using irradiance for rendering. In general, irradiance is different at every point, and can represent a large amount of information. The Irradiance Map GI method creates a map of this lighting.В Irradiance Map Settings can be accessed in the Renderer node > Renderer tab > Global Illumination tab. I've mostly found Vray to be incredibly intuitive, unfortunately this is the first time I've come across an area in it that is mental ray-esque in its lack of clear docs or workflow.Irradiance is a function defined for any point in the 3D space, representing the light arriving at a point and all the directions from which the light arrives. Map sequences seem to load without a frame extension, or at least that's how it appears inside Vray's render settings. Not clear what the naming convention should be when entering the map name when you are saving out a sequence. This is all further confused by the fact that reloaded maps cannot be opened in the irradiance map viewer (I get a wrong file type or wrong filename message, even though there is only file format that this feature appears to offer, i.e. Which mode will both render a frame sequence and write out reuseable irradiance maps? I also tried outputting a sequence of maps while also rendering, using the 'Single Frame' mode, but this appears to overwrite the same file over. On one machine I used the 'Animation (Prepass)' mode to output a sequence of maps, but when I reload these maps and change the mode to 'Animation (Rendering)' and render, It seemed intuitive enough at first, but I'm finding I'm not getting expected results. Can anyone give me some pointers on which mode I should use to bake out Vray irradiance maps for an animation?

Irradiance map vray settings