Brad, I would like to hear about your workflow. What part of the process did you use TurboCAD & SketchUp? Thanks.
I generally model in either TC or SketchUp and sometimes both. I find there are times when it's much simpler to accomplish something in one versus the other. I love the current compatibility between the two.
This time, the modeling was done in SketchUp only. I applied the materials in SketchUp and saved (2) 2D images. One containing the textures, shadows and environment with no edges, and one containing nothing but edges with jaggies and extensions turned on (black lines on a white background).
In Photoshop I used a combination of filters on the texture layer to get the watercolor effect. First was "Ripple" (Medium, 50%). I made 2 copies of the result and filtered one with "Dry Brush" and the other with "Watercolor". I adjusted the opacity of those over the "Ripple" effect to get the right mix.
TurboCAD's task on this one was to render some soft shadows. They are most noticeable in the eves and through the entry court. On it's own, SketchUp doesn't provide any gradient to the these areas, so they end up looking rather flat and monotonous once you go to work on the watercolor effects. I tried to render the soft shadows within SketchUp using Renditioner, but the settings had to be cranked up to get the result I was after and the rendering time was not good. So, I switched over to TC and got what I needed in about five minutes. I adjusted the shadows to taste using "Levels" and added some grain, then blended using "Multiply".
Now for the line work. I like to filter the line work in Photoshop with "Diffuse Glow". It gives the lines a grainy quality that mimics pencil lines when blended using "Multiply". Adjusting the opacity lets you fine tune the effect.
The final step was to create a paper texture layer and blend it over the other layers using "Hard Light".
Hopefully this all makes sense.