There are many things you can do to improve the realistic aspect of your render.
A easy but effective way is to use special image overlays to simulate scratched, dirty and smudged materials.
First you should think about what kind of imperfections your object could have? Is it a vehicle? Add some dirt and dust. A pair a wine glasses? Add some wiping residue or maybe liquid stains. On a phone? Fingerprints, maybe scratches?
After you know what you need a quick google search or a search on Poliigon.com wil give you some nice usable imagery.
Depending on the software you use, youll have to import images in diffrent places. In vanilla C4D you can create a second overlay material with alpha channel enabled. This way you can add your dust, fingerprints and dirt to this material and later apply it to any object.
In octane i found the best way to directly import them in the base material. For example in a glass material i will load wiping residue images in the Roughness channel. That way where the smudges are yo cant see through clearly.
Once you have figured out waht works best for you, the renders you output will appear more realistic than previous ones.
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