###### Descriptions and Examples for the POV-Ray Raytracerby Friedrich A. Lohmüller     3D Animations with POV-Ray         Some basics and examples on animations.
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3D Animation Tutorial
Index of Content
0. Basic Knowledge
1. Basic Example
2. Example 2
3. Images to Animated Gif
4. From Images to Video
> 5. Basic Terms
6. Animation Commands
I. Cyclic Animations
1. Rotating Objects
1.2. Planets in Orbit
1.3. Clock Animation
2. Rotating Camera
2.1. Straight Moving Camera
3. Western Wheel
Problem
3.1. Rolling Wheels
4. Gears
4.1. Roller Chain
4.2. Bike Chain
5. Swinging Pendulum
5.1. Newton's Cradle
5.2: Rock the Rocker
6. Spiral Pendulum
7. Coupling Rods
7.1. Connecting Rods
8. Psychedelic + Op-Art
9. Counters + Countdowns
10. Folding of a Cube
II. Non-linear Movements
1.0 Speed Up/Slow Down 1
1.1 Speed Up/Slow Down 2
2. Fall + Bounce
3. Acceleration by
physical Formulas
4. Speed Controll by
Spline Functions
III. Animation Paths
with Spline Curves
1. Spline Curves
2. Closed Splines
3. Animation Paths

# Technical Terms and Basic Knowledge

##### About frames, fps, bitrate, frame size, animated gifs, avi and mpeg.

Important Terms in Computer Animation:

frame = a single image of a movie, video or an animation. Each movie is a fast sequence of single images with only little changes in these frames, because of the inertia of our optical perception in our eyes this sequence is interpreted by our brain as a continuous motion!

fps = "frames per second" = the number of single images per second.
The human eye needs a sequence of about 25 single slightly changing images per second to give us the illusion of a continuous motion. A slower sequence seems to flicker.
In mpeg videos according to the mpeg-1 standard the following frame rates are allowed:

 frame rate (fps) time for a frame in milliseconds 23.97 fps 41,7188 ms 24.00 fps 41,6667 ms 25.00 fps 40.0000 ms 29.97 fps 33,3667 ms 30.00 fps 33,3333 ms

bit rate = the number of bits per second moved from a harddisk or by an internet connection (in Kbit/sec or Kbytes/sec). This value must be considered if a video or an animation is played on a computer from the hard disk or a CD ROM or by an internet connection.
An internet connection has a theoretical bit rate of about 20kbit/s to 64kbit/s with ISDN or about 700kbit with DSL connection. In reality we only will see a fraction of this!
With small mpeg videos bit rates are usually around 1200 kb/s = 150kBytes/s.
DVD-Videos should not have higher bit rates than the maximum of 9,8Mbit/sec.
The perfect bit rate depends on one hand by the image size and on the other hand on the quality of compression.
How fine a video file will play or come through your internet connection depends very strong on the bit rate we achieve here.
If the achieved bit rate is too low, the video will stutter, jumps over some images or the images show flickering squares or the video stops totally!

frame size = the size of the single images.
As bigger the image size as bigger the file of each single image, as harder and more difficult it is to compress the complete animation.
Using animated gif files there are nearly no limits.
Using mpeg compression the height and width must be dividable by 16!
Here a table of mpeg video sizes and the size of the single image files:
 image size number of pixels file size single image SIF: 352 x 288 101 376 pixel 297 kB others: 512 x 320 163 840 pixel 480 kB DVD: 720 x 576 414 720 pixel 1 215 kB 16:9 : 1280 x 720 921 600 pixel 2 700 kB 4:3 : 1440 x 1080 1 555 200 pixel 4 557 kB 16:9 : 1920 x 1080 2 073 600 pixel 6 075 kB

endless loop = a cyclic animation, playing endless: it starts where it ends!
This is a very popular kind of animation for logos and banner on websites. With a small file (animated gifs) we can make a continuous motion.

File Types and Compressions

Gif and animated gif files
With this file type images are reduced to 256 colours. A table of the 256 most important colours in an image is produced and the colour pixels were encoded only by their colour number using only one byte per pixel.
This file type is good for animated logos and text. This type can be shown by all internet browsers. It can be integrated in websites like any other kind of image.
This file type is not very good for videos. The small number of colors (the human eye can percept about 16 Mio. different colours = "true colour" 24bit/pixel !) results often in a too rough raster with images with fine colour differences. The compression of a true-colour image file is at least one third of the original length - video sequences fast become very big and hard to transport.

Avi video
This file type can be shown with the "Windows Mediaplayer", as long as we have installed on our computer the video codec used for this video.
It shows images in true-colour. The compression is much better than with animated gif files with a much higher image quality.

Jpeg and Mpeg

The mpeg video file uses the same type of compression like the jpeg type which is used for colour photos. This type shows images in true-colour and has the absolute best behaviour according the compression. The image quality depends on how much we compress the images and also it depends on the video codec which are used to encode the video. How to choose the parameters for compression to get optimal results is a thing of trial and error!
Also this video type can be played with the "Windows Mediaplayer".

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© Friedrich A. Lohmüller, 2009
http://www.f-lohmueller.de