A large part of my freelance business is taken up with "Concept Design" work. Concept Design is any sketch that helps a client visualize an idea or product. Most of this work had been Black & White, but recently I have used any medium necessary to get an idea across. This might include color artwork, computer generated designs, or even foam core models.
These are just a few examples of some of my Concept Design work:

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Simple 3D Model into Concept Sketches

This is an example of where I will first build a simple 3D model of an environment and use it as the under drawing for one or more concepts sketches.

From Digital Scale Model to Sketch

I have recently added SketchUp to my arsenal of creative tools. With SketchUp I can pre-visualize a concept quickly and easily, and most importantly, in scale. Once a base model is built I can find an aesthetic camera angle and print out an under drawing, confident that the structure will work for its intended environment. I then take traditional artist tools to create a final concept sketch.

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Whether creating a traditional elevation, or a full 3D model, the concept sketch is whatever it needs to be to communicate an idea to its intended audience. As the tools get more powerful and easier to use, an artist's ability to pre-visualize a concept becomes more diverse.

In this example the concept sketch was used to create a 3D model

Model by Anthony Lewis