First of all it is necessary to normalize normals so that the lighting calculates correctly on the model in question, in case the model has been scaled.
The second thing to consider is, the more triangular faces the model has, the better results you will get. A good topology is also necessary but I was not going to mention this because it is obvious.
The third thing to consider is the attenuation of the light, the more attenuation, the better the light quality, but it will reduce the amount of light emanated, to solve this you can simply add more lights.
If you have followed the second point (considering that irrlicht is fast enough to have this luxury that most engines cannot), you can correctly configure the spec
The fourth thing, and very important if you want to get realism, is to have previously baked textures, you can use Blender for this, I personally use Blender internal and set up a HDRI to get metallic textures.
An example:
Soon I will upload a tutorial on how to texture an object and get realistic results using Blender internal.
Blender internal is fast and when working with filters it has practically no noise, unlike cycles.
Blender internal render(5 sec):
Blender cycles render(9 hours):
Cycles texture bake:
Internal texture bake:
Each one has its pros and cons, the examples are without filters, with filters can reduce pixelization, although with filters in directx9 it looks much more blurred than in opengl.
I personally prefer the bilinear or trilinear filter(in directx9), because, although the images look more blurred, it is more comfortable for my eyes, personally speaking of course.
A bake in Blender internal takes seconds, in cycles it can take hours or days.
If you have the lighting off, you can still work with shadow volume on another object to get its shadows, this also helps to get realism, in the future I will talk about that and give examples.
