hi...
, the example that uve given here has all been painted, ofcourse good painting skill is required to make scenes appear as 3d. but remember, not all of them are like this, at times people do use outside elements, images, 3d renders to work furtner in photoshop. good examples are matte paintings, they can even be all painted, or in most cases, images, photographs, 3d renders are used in them, which give u good 3d depth. they are mostly mixture of everything. lastly, good painting skills are most important to have, no matter what your procedure is.
all the best...
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