How to create this torn pattern at the edge? For example I have a rectangle or a simple plane with simple color, but how to create this torn edge? Please help me... I beg you.
Yeah if you are just starting out it can seem impossible. It's like asking how long a piece of string is. There are lots of ways to model what you need and it depends on what you intend to use the model for. A combination of ZBrush and Marvelous Designer is popular at the moment. Here is a screen cap I made years ago…