I learned about radiosity sometime around 1996. The first program I used that could light a scene with radiosity was called POVRay. To get it to work you had to set up a whole lot of parameters just right. A few years later I illegally downloaded a copy of Maya. Maya could light a scene with radiosity, (called global illumination). Here again you had to set up a whole lot of parameters just right to get it to work. Besides, I didn’t like downloading software illegally. Then I discovered Blender (free software), but it could not render with radiosity. In 2009 I came across LuxRender. LuxRender will take a scene you’ve created in Blender and render it with beautiful radiosity and physically based materials. It was pretty easy to set up. You just assigned different materials to your objects, create an object which will serve as your light and export your scene using the LuxRender plug-in. Around December 2011, Blender released version 2.61 which included the Cycles render engine. Finally I could render with radiosity without having to export or tweak a lot of settings. Also Cycles allows you to interact with your scene while it renders with global illumination. Every time you make a change it immediately updates the lighting. Like LuxRender, Cycles starts with a very rough approximation of the finally result. As it continues to process the scene the quality gets better and better. For some scenes you may have to let Cycles render for hours and hours to get a good quality result, but boy do I love the results.
Below is a typical Cornell Box rendered with Blender Cycles. It took about an hour to render.
Here is a video of a camera turning around in a room lit by the sun coming through the window. I wanted to complete the render in less than eight hours so I kept the quality very low. Each frame has a quality of 60 samples. For comparison, the Cornell Box above was rendered with a quality of 8,000 samples.