A USAF Asteroid Hunter with a rough guide to workflow from Sketchup to Photoshop.
STEP 1: first export three images from Sketchup: 1. Shadow map 2. flat colour with hidden edges 3. Profile edges. I also took a Clay Render from Thea render with added glass reflections.
SREP 2: In Photoshop I layer all of the images in the following order (Shadow, lines, flat colour, clay render).
STEP 3: I set the line overlay to a multiply blending option.
STEP 4: I select the shadow layer and set it to 100 black.
STEP 5: I set the opacity of the Shadow layer to between 30-75% depending on the scene lighting.
STEP 6: From the flat colour layer I select various sections to be brought into the main scene. Here I have selected the window frames.
STEP 7: I can then change the colour, pattern or shading of individual elements. I often colour sections in very contrasting colours in SU so that they can easily be selected and modified in Photoshop.
STEP 8: Glass effects are easily produced using Gradients. Here I have used a default style and then changed the colour to Blue.
STEP 9: I can then add in many more details, for models such as this I often use decals scanned in from Airfix and model kits then brush them up in photoshop or illustrator.