In its turn, Photon map algorithm acts more rough. This way, the calculations are performed only the areas of the scene, which are directly visible from the current camera angle. That is, we can assume that the rays are emitted from the camera itself and then exams how much of other rays from direct or indirect light sources re reach this point. In the Irradiance map, creation of global illumination begins with a vector from the camera, which is fly into scene until intersects geometry, and then verifies how much of light is fall in that intersection point on 3d object surface. The principle of photon mapping is relatively easier to understand compared to how the Irradiation map works. In general, such map is similar to a map, which obtained by Irradiance map algorithm. The each point stores information about the brightness and color of the indirect illumination. After that, being formed a so-called photon map, that is three-dimensional map of photon’s contact points with surfaces. It is an outdated rendering engine, the basic concept of which is that the light source bombards all scene objects by portions of energy called photons. As you may have guessed, we will also take a detailed look at all the important Light cache settings in the illustrated examples and surely will learn about its optimal settings. Both solutions, of course, are designed to simulate diffuse reflection of light in 3D scenes.
![vray settings for realistic rendering vray settings for realistic rendering](https://wiki.mcneel.com/_media/rhino/architecture/vray/vray-rhino-overview.png)
![vray settings for realistic rendering vray settings for realistic rendering](https://img1.cgtrader.com/items/899190/0af8f550ce/large/sketchup-vray-3-4-full-scene-render-setting-lighting-and-hdri-3d-model-low-poly-skp.jpg)
Here we will look at a theoretically interesting but outdated and rough Photon map, as well as progressive and relevant today Light cache. In this tutorial, we continue or, better said, complete our familiarization with the various GI engine's of V-Ray renderer. Introduction Conservative Photon Map Progressive Light Cache Light Cache Calculation Parameters Light Cache Reconstruction Parameters Conclusion & Comments Introduction