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When doing a speed sculpt it's important to work on the big shapes and be loose and experimental. This allows you to make a whole bunch of character or creature concepts for a client (or yourself) in a short period of time, without getting stuck on details.
For this image, even though it wasn't important to add details like small wrinkles and pores, I found that I had the time to do so later on in my 3 hour limit. The majority of time (2hrs 45mins) was spent on modeling; the rest, and more, (1hr 10mins) was spent on the render.
I start the model by loading the DefaultSphere from LightBox (hotkey ","). I then pull this sphere a little with the Move brush, just to get basic shape to start off with (Fig.01). To avoid stretching, I convert the image to a dynamesh at a fairly low resolution (40), since I only want to work on the big forms at the beginning.
I start blocking out something that resembles a humanoid skull and chest. I find it useful to use the Trim Dynamic and Clip brushes at this early stage to get some coarse features in the model.
I now start scribbling out some features on the face with the Dam Standard brush (Fig.02).
These are used as a kind of sketch just to get my ideas flowing. I don't intend for these sketch carvings to stay there forever, so I can smooth them out later with the Smooth brush.
I also find it helpful to suggest the eye sockets and the cheekbones early on. When I started I didn't really have any idea of what kind of character I wanted, but now there is an idea in my head that he should be an ogre-like brute.
I continue working on the profile of the character with the Move brush. In order to make his lower jaw stand out, I mask it off with the Mask Lasso brush while looking at the model from the side. I then pull out the jaw with the Move brush.
Don't forget that you can move the faces in the brush's direction by pressing the Alt button while moving. I do this quite often as you don't have to rotate the model around when using this feature. It's also good to work with the Standard brush at a low Z intensity (Fig.03).