Some animators say using video reference is cheating. Don't be fooled by that. Since the days of the Nine Old Men—the core pioneer animators of Walt Disney Productions who created classics such as Snow White and Pinocchio, which helped define the art of animation as we know it—animators have studied and used video reference. The main difference is that today it's much easier and more accessible for us to do that.

Reference is something extremely important for animators to get inspiration from and understand the essence, physics, and motivation behind movements. From video reference you can get good visual ideas to apply to your animations, especially for acting subtleties, secondary actions and timing.

Blender allows us to easily insert videos or image sequences on the 3D View background to use as reference, and we're going to see how to do it. For this recipe, an excerpt video is used from a public domain movie called WILLIAM BENDIX IN RILEY, SAVINGS BONDS SALESMAN; maintained by the National Archives and Records Administration. It's available at http://www.archive.org/details/gov.archives.arc.11866.

You can also visit a group page on the Vimeo website, which is maintained by animators and allows you to watch hundreds of live action video footage for reference at http://vimeo.com/groups/aniref/videos.

How to do it...

1. Open the file 006-VideoReference.blend. It has our character Otto in his resting position. In the support files there is a file called 006-VideoReference.mp4, which is an excerpt from a public domain video encoded with a MPEG-4 codec and a frame rate of 30 frames per second. We'll use it for help posing our character.

   Note

   Most common video containers and codecs are supported by Blender to be used as background. Movies in .mov, .avi, .mp4, or .flv can usually be loaded without any hassles.

   Tip

   Knowing the frame rate of the video is essential, because our Blender file has to match it. You can discover the video's frame rate using the free and cross-platform multimedia player VLC (available at http://www.videolan.org/vlc/), by opening the video with this player and pressing Ctrl + I to see the media information. The frame rate of the video is shown in the Codec Details tab.

2. Go to the Properties window, on the Render tab, and find the Dimensions sections. Change the FPS field to 30.
3. Go back to the 3D Window, and open the Properties panel (N). Scroll it down until you see the Background Images section. Enable that option, click on the triangle on the left-hand side and click on Add Image to access the background settings, as seen in the next screenshot:
   

   After clicking on the Add Image button, a new slot is created so you can select a background image or movie.

4. To select the file, click on the triangle next to Not Set. A new set of buttons will appear on the bottom, where you can select an existing file within Blender or select an external one. Click on the Open button to look for our video file. The window will turn into a file selector, and you'll be able to see thumbnails of the video and image files to find what you want easily.
5. Click on our video file and then on Open to load it into our scene. Blender will automatically set the first frame of the movie as the background, and our panel will change to accommodate more settings, as you can see in the following screenshot:
   

   Among these settings, it's important to enable the Auto Refresh option, which will update the viewport when you change the current frame in the timeline. There are also two similar options: Start, which tells Blender to start the background playback on a specific frame, useful for when you want to use the reference on a later part of your animation; and Offset, useful if you want the first frame of your timeline to be synchronized to a later part of the reference movie. There are also quite easy to understand settings such as Size, Transparency, X and Y, to control size, opacity, and position.

   Since the video reference uses a real world perspective, using it in orthographic views doesn't make much sense, as these views are only mathematical representations of a real perspective. We can tell Blender to use the background video only in the Camera view, with a matching perspective.

6. Select the Camera option in the Axis field in the video reference slot. Now, you'll see the movie as a background only when in Camera view (Numpad 0). A good use for this setup is with the Quad View Ctrl + Alt + Q, which is new in Blender 2.5 and divides your 3D window in four views: Top Ortho, Camera Persp, Front Ortho, and Right Ortho. After enabling it, you'll be able to pose your character nicely within the views and have your background video set only in Camera view, as seen in the next screenshot:
   

   Another nice thing about using background videos and images in Blender is that you can use more than one at a time.

7. Click one more time on the Add Image button in the Properties panel to create another image slot. Repeat the same you did for the movie file, but now select the image called 006-VideoReference.png in the same folder and set it to be shown only in Camera view. It's a grid with the Rule of Thirds to help you set up your camera and achieve a better visual composition. Set its Transparency value to 0, so it's fully visible on top of the video reference, as seen in the next screenshot:

The file 006-VideoReference.blend has this complete example, so you can refer to it and compare your results.