BLENDING TWO MATERIALS SMOOTHLY

This tutorial is going to show you have to use the blender node to merge two materials smoothly half way across a prop or surface. This could be used to give a dramatic transformation, as in figure 1, or a more subtle one, replacing a detailed foreground material with a simpler background one without leaving a visible seam.

Fig 1: Blending two materials smoothly

This technique needs a minimum of three nodes. First, we have our blender node. This does the actual blending. In Figure 2, we have plugged a cloud node into Input_1 and a weave node into Input_2, but you could just as easily use simple colours in the blender node instead.

To control our blend, we will be using a modified U node. This will make our materials merge from left to right - if you want them to merge front to back use a V node instead. This U node is plugged into a maths node, which is going to modify its output.

Our blender node is controlled by the Blending input. Black areas on the input result in Input_1 (our clouds), white areas produce Input_2 (the weave), and shades of gray produce a mixture. If you plugged the U node directly into the blending input, our two materials would be merge all across the the result. We want to limit the merged area to the middle, so we need to alter the output of the U node.

We are going to do this with a maths node. Set the argument to subtract, and plug the U node into value_1. Plug the output of the subtract node into the blending input.

At the moment, the result is the same as if we had plugged U directly in, but we are going to alter that. First, we will change value_1. In our sample (below) this has been set to 3. This will multiply the U node input by 3, resulting in a gradient that runs from 0 to 3. The blending input takes any value above one as a one (white); and any value below zero as zero (black), so at the moment our clouds start to fade out immediately, and are gone one third of the way across the material.

We are now going to move that blending zone across the material. To do this, we change Value_2 to 1. This produces an output of -1 to 2. Remember, anything less than zero is treated as zero, and so our clouds now spread across the first third of the material, from -1 to 0. The middle third sees the blended area (0 to 1). Finally, the final third sees just the weave (1 to 2).

Fig 2: Node setup

Value_1 and Value_2 can be altered to control how big the blended area is, and how far across the material it appears. The larger you make Value_1, the smaller the blended area. The higher you make Value_2, the further to the right it will start. If the two figures are equal, then there will be no blend zone (if both were set to 3 for instance, the range of figures would go from -3 to 0).