instead of creating a thread each time, i’ll post my questions here. so what does that Unreal doc sentence means
Shading models have a cost: Unlit is fastest, Lit is what should be used mostly, and other models are more expensive.
what is a shading model. does that mean PBR. does it mean what has been already said sooner in the doc, that we should avoid complex materials as much as possible
and somebody could show me (ideally a pic) what this is
Limit the attenuation radius and light cone angle to the minimum needed
and
Decal performance cost scales with the number of pixels they cover.
Hi and welcome!
Your questions are not 100% clear, but I’ll try:
A shading model is like a base for your material. Each shading model is made to handle lighting etc in different ways. For example, since skin differs quite a bit from metals and dielectric materials, there are the “preintegrated skin” for skin materials and the “default lit” for pretty much 98% of all the assets you will make.
If that makes sense. Some are more expensive than others, based on their complexity. “Unlit” is cheap because it doesn’t have to do any complex calculations at all, while the “preintergrated skin” is more expensive due to the complexity of calculating correct subsurface scattering, lighting and shadows.
Attenuation radius is the maximum radius a light can affect something. Since light intensity follows a logarithmic scale, a weak light will not really affect objects after quite a short distance thus would it be useless to have a large attenuation radius. While on the other hand, having a short attenuation radius on an intensive light will make the light behave unrealistically.
From the documentation:
"The Attenuation Radius of the light does a few major things:
- Sets the reach of the light.
- Defines what objects it will affect.
- Serves as the outer bounds when calculating the falloff of the light."
Just means the larger the decal, the more expensive it is. Since the decal operation has to be calculated for more pixels 
thanks. #1 still bit confused. but i think, i’ll get it once i’ll have made my first skin material 