Compositing Methods

While you can create a scene that is rendered exactly as you need it, it is usually faster to get something close to the desired result and then make the final modifications in the compositor. This method provides very quick feedback and making changes to the lighting and color with nodes, for example, is much faster than rendering the scene again. Sometimes, you need to render different elements in different layers and then combine them in the compositing. Maybe you just want to place a 3D object into a photo or real video, so you might need to mix your rendered 3D object with those images and adjust their colors so the lighting and contrast fit with each other. You can do such things in other software, such as Photoshop or Gimp, but you can do them in Blender as well.

There are usually two main methods for compositing: One way is to do the compositing before the rendering. You take a test render, composite it in the Node Editor, and then launch the final render (even an animation) with the effects of the compositor. For this, you use the scene render as an input.

The second way is to do the raw render of elements and then load those image sequences or videos into the compositor to adjust them. This also allows you to adjust videos, of course. Imagine that you take a video and you want to add some color correction to it: just load it into the compositor, composite it, and render it—no need to use the 3D View.