According to this page, virtual texture coast has two categories: lookups and stacks.
If two virtual texture uses the same uv, stack coast can be saved.
You can view lookups and stacks counts in the material stats.
When you are using Material Blending node with the value sampled from a virtual texture as the alpha value, the counts have unexpected results.
In above image, there are 3 virtual textures and all of the uses the same uv,
so there are 3 lookups and 1 stack, and the stat also shows the expected result.
I expected the same counts when material blending node is used instead.
However, actual result is not what I expected.
There are 5 lookups and 2 stacks. 2 more lookups and one more stack than expected.
If I use just a constant alpha value on the material attributes blending node,
it gives expected result: 2 lookups and 1 stack
So I simplified both materials, only using one virtual texture to get the alpha value.
Material with linear interpolation node gives expected counts. 1 lookup and 1 stack.
Material with attributes blending node gives 3 lookups and 2 stacks
It seems using VT sampling as the alpha value for Material Attributes Blending node gives 2 extra lookups and 1 extra stack.
Does anyone know why this nodes gives these extra counts?