Light portals are a method of reducing noise, which, as you already noted, is new in 2.75. Light portals help to remove noise by guiding rays from the environment through the opening where a portal is positioned. Because of the fact that they are designed for openings, they are most useful for a...

I have an OBJ file that has two meshes mapped to two different texture files. After cropping the meshes in Blender, I realized that most of the original image portions in the texture jpegs are not being used. Hence I want to combine two textures into a single texture and export the meshes into ...

Here's a example I made a long time ago using the same techniques. https://www.youtube.com/watch?v=Krn7CrYg4h8 This can be done easily with some render layer trickery. Start out by putting both of your scenes on two separate layers, and align everything so that in your first scene, the opening...

Often times to control parts of the game that are kinda background or sidework, we add empties. Invisible empties can be used for playing sounds, loading levels, spawning bad-guys, or running pythn scripts. Create an empty that will run your script if it doesn't need to be on a specific object ...