Iterative blur levels via resolution reduction.
The first blur texture (blue) is available in
the full basis texture resolution.
Then the texture edge length is divided in halves with each level.
The blur shader itself is separated in a horizontal and a vertical pass.
Basis for this demo is a progressive
image-based Julia fractal render.
In the composite shader all the textures get layered on top of each other,
using the mix() method.