Making and asigning a normal(or bump) map from image texture just using nodes

I am making quite low poly green hedge (with just a little beveling on the edges). I have it textured and now I remember I have seen a tutorial how to generate and assign a normal (or bump) map from the image textures using just nodes (not making and assigning separate normal/bump map).
Does such “utility” exists and if exists a link please or I have mistaken something?

Making normal textures is already something not easy to grasp. Making them from textures is even more limited.

The problem is that textures only have specific data, and normally that data is not related to the normal information. The best approach (and typically more complicated) is to have textures (or any other data container, normally an high poly version) where the data can be used to create colors, normals, roughness, glossiness, etc maps…
But there’re methods to abuse some texture types in order to create a normal map. For example, finding the derivatives in a color map can be used to create a normal map. Thought this is somewhat clumsy and prone to strange results (dark colors will be treated as sunked areas and vice versa). Some other technics use convolutions of the derivatives to produce a better result, but still it always depend on the quality and type of texture you’re using as input.

Blender itself doesn’t have a direct way to do this (except for the bump, which is a derivative method), although one can use blender to execute most (if not all) methods of extrapolating normals from textures.
Other softwares offer more a good collection of methods that sometimes create maps good enough for quality use… ‘CrazyBump’ comes to mind.

Tell me please what mistake I do. I see the green hedge texture in display material mode and when rendered but see the normal map when in display texture mode.


booxhedge.blend (9.33 MB)

Texture display mode shows the texture in the last selected texture node.

Thanks. Every time I learn something new, I understand how many small details I still have to learn. Sigh…

Edit: some more help please
I remade the hedge in quite simple model - just extended cube with just 6 faces. But I unwrapped all the 4 side faces with a texture with a transparent top.
So the question - I know I can put a “fake” face just where the transparent part starts and to slap the top texture upon it; BUT - can I put the top texture upon the existing top face above the transparent part in such way it still to appear not above the transparent part but under it making a natural top of the hedge? Also can I use a noise texture to make the top texture more realistic but still low poly?


booxhedge.blend (7.06 MB)