Think of Pencil (free) as an animator's digital sketchbook. It's 2D; you can sketch things very well, then refine them as they take shape; and it's small enough you can carry it around with you on a USB drive. However, just like a sketchbook, this open-source program is a work in progress--and as such you might not want to use it with your professional portfolio.See all Graphic Design Software reviews.
In some areas, Pencil excels. The drawing tool is a highlight for anyone who prefers paper over digital drawing. The pressure sensitivity in Pencil with my Wacom tablet and pen worked better than any other program I've tried it out on, including Adobe Illustrator.
This strength alone doesn't make it a great drawing or animation tool, since this version of Pencil can export only as XML, a sequence of PNG images, or Flash movie; and it doesn't upload directly to YouTube or Facebook like many other (costly) animation programs available. An addition of export to EPS or TIFF would make Pencil very appealing to artists; JPEG and PDF would be useful because of their many Web and business uses.
One of Pencil's best features is that you can add as many raster, vector, sound, and camera layers as you need to the same animation, and set the frames independently. The odd thing is that you can only use certain tools on certain layers: the Pen on raster and the Coloring tool on vector. It would be a huge improvement--and reduce the frustration level--if Pencil grayed out the tools that won't work on the layer selected.
The layers work much like layers in any other drawing program--Illustrator, Paint.NET, Serif DrawPlus, and so on--but it's not always easy to see what you're doing, which layer you're working in, or why part of the drawing you're trying to manipulate just isn't changing. See all: PC Advisor software downloads
Oddly, for a stop-motion animation program, Pencil doesn't seem to have a duplicate frame menu item or button. However, unlike other basic animation programs, Flip Boom Cartoon or Animation-ish for example, you don't have to add in every single frame. Pencil instead assumes that you want the image to stay the same along the timeline until you add in a new key frame. This allows you to easily create smooth animation without duplicating every single frame.
The oilskin function in Pencil allows you to trace from one frame to the next, or from a previous frame, which is how you fill in the gaps between your keyframes. If you are new to the process of stop-motion animation this can be very confusing, and unfortunately the only help options beyond a very basic manual are the online forums. However, the community there seems extremely willing to help even a noob.