Drawing symmetrical objects in perspective can be a challenge. In situations like this, I generally use Google Sketchup to help me with my accuracy This video explores the powerful tools that Sketchup provides for working with repeated shapes and symmetrical forms. Even if you're saying "Yeah, yeah - symmetry is no big deal in perspective..." would you change your tune if I asked you to draw an object that 7-sided with rotational symmetry? Sometimes a little bit of 3D saves a lot of time.
Whenever a new medium emerges, artists are quick to dismiss it as inferior -- and digital painting has been received negatively by many artists. This video is my attempt to argue in favor of digital painting. Of course, there's no correct medium to work in. Working digitally, though, brings some wonderful new opportunities to the table. Besides, when was the last time you hand-wrote a letter? With my commercial work I find the best solution is almost always a combination of tools: some 3D, a little photo-texture, lots of reference imagery, and digital painting to pull it all together.
Thumbnail sketches are small drawings which help plan your larger, finished, works. There's noting 'finished' about them, and they are generally thrown away once you begin the final piece. So why not use 3D software to help generate some ideas? As far as 3D software goes, Sketchup is very basic and straightforward. Even if you aren't interested in making complex models in 3D, doing a quick block-in of your scene and then moving around it in 3D space can help you select dramatic camera angles.
Have you ever tried 3D modeling before? Many digital painters answer "no" to this question, though even a small amount of 3D experience can make a huge impact on your paintings. This video introduces Google Sketchup as tool for drawing. As it states in the video, the word 'drawing' can mean many things - so if you're going to paint over it anyway, why not use some 3D modeling as a foundation for your work?