issue with normal maps on character

I’m in the way of learning Blender.
I’ve modeled a lowpoly character, unwrapped, assigned material and textures for diffuse color and for bump using nodes. Animated it, rendered using cycles. So far so good.
Then I wanted to make a normal map so i duplicated my mesh, applied multires and sculpted a denser mesh then baked a normal map texture.
All well except when I apply this texture to the low poly model all the seams of the unwrapping shows as if the normal where uncorrect joining and that is pretty strange as both models share the same exact seams and unwrapping.
I tought it could be an interference with other textures so I tried basic materials with normal map textures only. Nothing changed.
tried different types of normal mapping with different results but allways with seams showing badly.

my nodes for material are
image texture node - color (normal map texture) --> color -normal map node - normal --> normal - diffuse BSDF --> output

So I tried a different way
I baked normals from HighRres model to the Lowres directly
This time if I set normal mapping to object space the seams disappear and the normal map do his work BUT it also shows the faces of the low poly mesh as if it was in flat shading (see attached pict).

This really puzzle me.
Shading is set on smooth. If I disable normal map node the model is smooth shaded.
The normal map texture is smooth. Absolutly no sign of faces in the texture itself
There are no seams in the faces marked by arrows btw

I’m following many tutorials but cant understand what I’m doing wrong. Please give me some hints

Sorry for the long thread. thankyou in advance

Is the image texture node set to “Color” or to “Non-color Data”?

in the picture is set to color but also tried non color data

Maybe my problem is not related to normal textures. Well, not only to normal textures

This is the basic scene cube, in shade mode, with 2 subdivision in subdivision surface modifier, cycle render and a basic diffuse --> output node.
Even at this level there is something wrong
Why faces are visible?
Why shading is not uniform?
If I make a sphere and set it to smooth shading the faces are not showing.
I also tried to add a edge split modifier with 180° angle (should make it completly smooth) but the faces artefacts keep showing
BTW the faces showing are not the former borders of the cube
Any ideas?

What you see there is the so-called “terminator artefact”.
In a nutshell: Smooth shading is a trick that can only go so far. When high-contrast lighting meets low-poly geometry, that trick will fall short and the shadows will terminate in an incorrect way - that’s an issue very many unbiased render engines suffer from. So, either use a larger light source (to “soften” the shadows) or increase the density of the mesh (higher level of subdivision, for example).

If you don’t see the terminator artefact without the normal map, chances are the terminator issue is not to blame for the effect you see on your ogre/troll mesh.

And btw, normals maps always need to be set to “Non-color Data”…

Did you try Edge Split Modifier, and different angle values?

thankyou for your detailed explanation.

At first my scene had 2 area lights.
tried to pump them up, scale them up and also change their square size in light panel. Nothing change except of course scene lighting intensity.
BTW why scaling area lights wont change their size in light panel?
Then I tried adding other light sources

I think it’s a true problem with normal as i’ve played with lights quite alot
in the picture you see the model with a denser mesh (surface subdivision) on the left side normal maps applied (some bump too but disabling bump wont affect the scene)
I think I will try on another model to see if it’s the same

yes I did but a 180° angle should provide smooth shading in any condition.

Did you bake the normal without smoothing on? Polygonal artifacts can show up in normal maps if you forget to use smoothing while baking them. This goes for subd surfaces as well, you will have a bunch of small scale squares all over. Ticks me off when I forget to use smoothing while baking smooth objects. And of course, as said above, use Non-color data.

No ajm
I made again the baking process to be sure
both high and lowpoly models are in smooth shading before baking
normal exported baking in tangent mode
Normal applied to lowpoly mesh using tangent mode and non color data

After Ikaishinjii suggestion I searched for terminator artifacts and youtube showed a video with a very similar situation (lowpoly+normals).
video name’s Low poly artifacts in blender cycles (terminator effects)

Do you know any method to avoid it?

As for lights.
Do you know what is the differece between scaling a light (S) and changing his square size?
changing the size will reflect in a bigger size in viewport while scaling the light in viewport wont change the size value in square panel

Not off hand, no, sorry.

This is not a normal map problem. It is because of Cycles. Your model needs more subdivisions or bigger light shadow map values (smoother shadows).

IkariShinji already described it well in his post.

You can change the renderer too. For example use the blender defalt raytracer instead of Cycles. Cycles is good for high poly models or beveled objects. At the moment you will always get this issues with lowpoly models in combination with normal maps in Cycles.