I recently described how to render a complete animation in the compositor. To achieve this effect, I used a texture which was modified in the compositor so that the scene didn’t need rerendering. The texture node has two inputs: scale and offset. Their color is violet, which means it needs some vector coordinates as input – but there is no vector input node available.
While I wished I had a vector input node, I found out that it is possible to connect an RGB node to the inputs, which worked, but had the limitation for values being in the range from 0 to 1. This was just enough for my uses, but it might not be for yours.
Luckily enough, I now figured out how to simulate a vector input node using a compositor node group. First thing to know is that R (red) maps to X, G (green) maps to Y and B (blue) maps to Z. Next, colors in Blender can actually exceed their range from 0 to 1. Anything greater than 1 will be displayed as 1. But for this vector input node, we needn’t care about this, because it will not be used as a color – but if you once need an oversaturated color, you can use the same approach. The pure R, G and B colors are multiplied with the input values of the compositor group and added together for the final vector output.
With this set up, you have a reusable vector input node group which you can save in a separate file and link or append to your scenes. The main benefit is, that you can now set keyframes on the X, Y and Z values which is not possible in the texture node offset or scale directly. So now the texture can be animated in the compositor. Another use for this node could be the vector blur node which has a speed input connector.