In this short basic tutorial on Compositing in Blender, we will see how to create and rename parameters for a node group and how to create a couple of parameters to adjust the intensity of the Vignetting effect.
Video Transcript
Hello everyone! In this short basic tutorial on Compositing in Blender, we will see how to create and rename parameters for a node group and how to create a couple of parameters to adjust the intensity of the Vignetting effect.
The tutorial was made using Blender version 3.6.
In a previously published tutorial, I showed you how to append a group of Compositing nodes from an external Blender file, and I also provided a file containing a couple of groups for free, implementing a glow effect and the vignetting effect.
However, the Vignetting node group does not have external parameters, which means that every time we want to modify the blur of the halo or the intensity of the effect, we will have to open the group and modify the parameters inside it.
This can be quite annoying, especially when dealing with many node groups implementing different effects, and not knowing all the parameters and their functions; moreover, having an input socket for some parameters of a group allows you to link those values to other nodes, such as a Time node, which allows you to adjust the effect based on the current frame, achieving animated effects, just to give an example.
To display one or more parameters of the nodes inside the group in the node interface when it is closed, simply open the group and create a connection between the parameter we want to display and the empty socket available in the Group Input node. It's very simple, isn't it?
For example, we can connect the Factor socket of the Multiply node available in the Vignetting group to the Group Input node, so that we can modify the intensity of the Vignetting effect when the node is closed, without having to open it.
Before moving forward, though, let me give you a suggestion: select the Group Input node, open the Group tab in the Sidebar (which can be shown or hidden using the N key), then select the Factor input and rename it, for example, to vig_intensity, or with any other name more meaningful than Factor.
Here, there are no other parameters named Factor in the group, so there's no risk of ambiguity, but in groups where two or more parameters with the same name exist, it's good practice to rename them in the Group Input node to ensure you're modifying the correct parameter... and indeed, even when the parameter is unique, giving it a more meaningful name is a good idea.
So let's move on to the second topic of this tutorial, which is how to create a parameter to modify the blur size of the Gaussian blur to be applied to the white oval mask on a black background created with the Lens Distortion and Greater Than nodes.
The Factor parameter of the Multiply node indeed allows adjusting the intensity of the application of the blurred mask, but not the blur size, which is determined by the X and Y parameters in the Blur node...
...however, we immediately notice that there are no input sockets for these two parameters, so we cannot connect them to the Group Input node!
Fortunately, the problem is easily solvable: it will be sufficient to set 100% for both the X and Y fields, then connect the Size parameter to the Group Input node and rename it, for example, to Blurring Size.
The Blurring Size parameter should be set to a value between 0 and 1, where 1 represents 100% for both X and Y. So, if we want a blur relative to 20%, we should write 0.2 in the Blurring Size field.
Of course, I told you to set 100% for both X and Y because their values were identical, so Size will modify both of them with the same proportion.
Now we have the node implementing the Vignette effect in a compact version showing two parameters, allowing us to adjust the final effect more quickly and connect them to other nodes if necessary, for example, to modify the effect based on the animation time or other parameters.
Well, I hope this tutorial has been helpful to you! See you soon!