Visual Effects are mostly powered by computer software. They are powered by the software. These visual effects or visual creatures are all based off of the computer. If the visual effects software that you are using dosn't have the right visual effect than you can always add more effects to your software. Visual effects, almost all of them have to be hand coded. If ever a movie needs a visual effect that is already provided they have to hire a person(s) to code them the visual effect.