Consider as an Architect, you begin with an undeveloped or blank site. Following an analysis of the zoning and code requirements, that will impose limitations. Once past the constraints, you begin the creative process. Your mind, begins to compose the form of a building. At the same time you define the shape predicated on the flow of the interior space. Both the inside and outside must be considered in harmony. The last phase, is the selection of the skin that will cover it and its color. All this would be a product of your creative mind.
Second as an Artist, you begin with a blank canvas. You may intend to do a landscape or a portrait or a simple non-objective painting. Whatever the subject, the imagination of your mind will be the guide. Although the landscape can be a copy of a view, it is your choice within the view. Do you compose up close? Or view from a distance? How you may interpret the product of your creative mind. What kind of brush stroke? Vibrant colors or soft? Do you deal in showing detail, or is it soft and flowing?
Third as an Author, you begin with a blank page. Fiction lets your creative mind invent the scene and the story. The story could be quiet or screaming. Do you chose the characters from friends? Or perhaps movie actors? Or do you invent the personalities or make them composites of known characters? Are the events from your experiences or simply your imagination? As colors in a painting the plot can be intense or soft.
The common denominator for me, is the creative journey.