Let’s assume you have a scene ready, and that you want to render it with the Radiosity Rendering. The first thing to grasp when doing Radiosity is that no Lamps are necessary, but some meshes with an Emit material property greater than zero are required, since these will be the light sources. Emit is found on the Shaders panel in the bottom right (Material sub-context). Typically, a value of 0.5 or less gives a soft radiance.
Renderlayers are used to separate your composite image into layers. Use RenderLayers for a specific reason - such as creating depth of field, relighting isolated elements within the image via a normal pass, adding a colorcast to specific portions of the image, etc. The keyword here is isolation. Renderlayers allow you to dissect, effect and or correct individual elements or groups within your composition before outputting your final render. This saves you from endlessly re-rendering your scene just to find out whether a correction is going to work or not.
We know that around the world, our users have PC's of widely varying power. Rendering is the process in CG that can chew up CPU and disk space like no tomorrow. Especially in corporate environments, it is easy to fill up terabyte servers by uploading ten hour-long DV tapes and doing some editing. So, there are lots of options try to shoehorn a big job into a small PC by providing you with multiple sets of options that chunk up the work as best we can, while still preserving image integrity.
This page discusses the main options found on the Render panel, and subsequent pages give you more.
Blender produces all the information needed to render a scene. While it has its own internal rendering engine, you can export or link to external renderers for image computaiton.
This panel provides many options for rendering, increasing and optimizing your render and output speed, and the location for displaying and saving your render output. The options on this panel control where and how the results of a render are handled.