Why do animators draw

Basic animation techniques

Basically, a distinction can be made between two- and three-dimensional animation. Like classic cartoons, 2D animations usually use more stylistic representations. 3D animations, on the other hand, try to look as (photo) realistic as possible and are therefore comparable to video recordings. This representation is limited to 2D animations. The techniques for 3D animation are mostly similar, but much more complex - on the one hand because a third dimension is added, on the other hand because a number of other properties must be taken into account in order to generate photo-realistic images.

What all techniques have in common is that the illusion of moving objects is created by showing individual images very quickly one after the other. This corresponds to the functionality of a flip book. However, the techniques differ in how these frames are generated. The spectrum ranges from the manual drawing of each individual image, through key scenes, lists with animation steps for individual objects to the automatic drawing of the scene using computer algorithms (Steinmetz, 1999; Khazaeli, 1998).

Single image animation

With this type of animation, each picture is drawn individually by a person. The single-frame animation is used when a sequence of movements cannot simply be generated automatically. This is the case, for example, for scenes in which many details, in particular the shape of the objects shown, change at the same time. Think of a butterfly flapping its wings or a person whose arms and legs move while exercising. For human perception, the relationships between the various body positions are easy to understand, although the contour changes completely. Therefore, tracing the contours is not a problem for an experienced draftsman. A computer, on the other hand, is not easily able to create these individual images. For this purpose, computers require complex 3D models, the construction of which is more complex than drawing the individual images by hand.

In this animation, each picture was drawn individually

Keyframe animation:

Of course, the star artists at the animation studios did not draw every picture themselves, only key scenes. The monotonous drawing of the intermediate images was left to draftsmen. On the PC you become a star draftsman and leave the work to your computer, because for many animation sequences it is sufficient to define key frames. The many individual images in which the intermediate steps of the change can be seen are calculated by the animation software. This always works very well when objects change linearly. Examples are the change in position of an object or the uniform change in size, brightness, color, transparency or even shape. The generation of the intermediate images is called tweening (short for in-betweening).

Imagine a car going straight from left to right. In this case, the first keyframe would be the car on the left edge of the scene, the second keyframe shows the car on the right edge of the scene. The individual intermediate positions of the car are easy to determine, so the individual images can be calculated automatically. To make a single movement look even more natural, many programs allow an object to move slowly at first, then faster and then slower again at the end - the individual movement distances are calculated automatically.

The animation was created by two key frames

Animation packages often use a timeline. The timeline consists of alternating key frames and intermediate frames. As a user, you only have to define the key frames, the frames in between are generated automatically. The number of images between the key scenes determines how quickly a movement takes place.

The automatic generation of the intermediate images is most often used for position and size changes. It works best there too. On the other hand, changes in shape are problematic, as these usually happen very unevenly. So it's easy to convert a circle into a rectangle. But what rules are used to calculate intermediate views if the first key image shows a moving car and the second a destroyed car that has hit the wall? In this case there is no avoiding single-frame animation.

The example shows the incorrect calculation of the intermediate steps

Changing from one representation to another is also known as morphing. With the help of special morphing software, the user can define additional clues as to which contours in the second key frame correspond to the contours in the first key frame. This increases the quality of the automatically generated images. If the changes are not too great, such as the transition between two faces or the transformation of related animals, then the results are very good. Since you can follow exactly which contours correspond to each other during morphing, similarities and differences between similar objects can be visualized through such animations.

Combination of single frames and key frames

The animation techniques with single and key frames are not mutually exclusive, but can complement each other. Key scenes can be defined not only with static images, but also with animated image sequences. The change of an object itself happens like in a single image animation in that single images are displayed one after the other. With the help of the key scenes, however, you can now define more precisely how and where these individual images are to be drawn. An example illustrates this. You can create a single frame animation to define the individual arm and leg positions of a person moving. You can then use this animated person in two key scenes in different positions. When creating the overall result, the individual intermediate positions are calculated automatically. The following picture of the animated person is drawn at each intermediate position. When an image cycle of the animated person has been run through, playback starts from the beginning. You therefore have to draw far fewer pictures for the more complex individual image animation, since repetitive motion sequences are used several times.

Any number of animated objects can appear in a keyframe animation. It is even possible to use one keyframe animation in another keyframe animation. Animation packages such as Flash allow animations to be nested as deeply as desired.

Path animation

The use of key frames is too imprecise for some movement sequences, as the following example demonstrates:

The ball moves rigidly to the defined key positions. In the real world, however, it would follow a gentler, curvilinear path. The technique of path animation meets these requirements. You can draw a motion path for an object along which the object should move. You can use lines, smooth curves, or freehand tools to draw the motion path.

Path using a curve

Another property of path animation is that objects not only move along the path, but can also orient themselves along it. This means that an object also rotates while it is moving. The slope of the curve serves as the angle of rotation for the animated object.

Animation lists

In this form of animation, one starts from a single image scene and defines actions in a linear list of how this scene should arise and / or change. The best-known example is probably the custom animation in PowerPoint. With this presentation software, individual slides are designed with graphic objects, e.g. B. Texts, diagrams or images. Animation lists are used to determine how and when the individual graphic objects should appear, change or disappear. Each individual action describes exactly one animation sequence, e.g. B. flying in a picture or changing the color of a frame. The animation duration is set as a property of the action.

Custom view in PowerPoint

The exact animation flow can be controlled to a limited extent. This allows you to specify which animations should start with one another or one after the other and how much time should lie between the animations. Most importantly, an animation can pause until the user clicks the mouse to continue. In this way, the animation can be controlled during playback, albeit to a very limited extent.

A somewhat more refined variant are animation lists that start with specified user inputs, for example when clicking on a graphic or when moving objects to other areas of the screen (drag & drop).

Animation with script languages

The animation with scripts is also based on changing an existing scene. A script is a relatively simple and straightforward computer program that was formulated in a scripting language. The graphic objects in a scene can be changed and animated with special commands. The graphic objects themselves can be animated images (“sprites”).

Many animation packages have their own scripting language (such as Lingo in Director or ActionScript in Flash). Typical commands are changing the current position on the screen, changing the size or showing and hiding a graphic object. The advantage of a programmed movement is that you can react to user input and the current surroundings of objects. With the help of simple if-then control structures it can be decided how the animation proceeds, e.g. B.

  • If the object hits a wall, change direction!
  • When an object collides with another object, start an animated explosion!
  • When object A is pressed, the movement for object B begins!
  • When the mouse is over an object, slow down the movement of the object!
This example shows the animation by programmed changing of the object position

Script languages ​​can also be used to define and calculate complex motion sequences. If motion sequences are to follow physical laws, then the mathematical formulas for calculating positions can be implemented in the script language. As a programmer, you don't have to worry about the display of the graphic objects themselves, you just change the properties, such as position, size, color or transparency.

The programmed animation steps are often started when certain user inputs (mouse clicks, mouse movements, input keys, drag & drop) have been made. Here, too, the programmer does not have to worry about recognizing these inputs. It only defines the response. Scripting languages ​​are therefore a good and - relatively - easy way to create interactive animations.

Animation with calculated individual images

However, sometimes it is not enough to simply rearrange graphic objects. If complex changes are represented, then the images must be created individually - similar to the individual image animation. But instead of drawing the individual images by hand, computer algorithms are used to generate the images. This is often the case when simulations are to be rendered visually. When graphically displaying changing parameters, each individual pixel may have to be drawn differently.

Libraries with graphic functions are available in many higher-level programming languages ​​for generating the individual images. Common functions are the drawing of points, lines, rectangles, ovals, texts, raster graphics and routes.

The following example simulates a car journey. The course of the road is redrawn for each individual image using calculated coordinates. When a single image has been completely drawn, it replaces the last displayed image on the screen. The end user only sees fully drawn images that combine to form a continuous flow of movement:

Simulation of a car ride

This form of animation development is the most flexible but also very complex. It is usually reserved for software developers.

Animation effects

Effects are a special case of calculated animation. Manipulations can be applied to existing images to create special effects. Examples are cross-fading effects between images or two animated image sequences, the blurring of animation sequences, the creation of ripple effects over an image, or individual image segments flying apart like an explosion. The algorithms required for this are also very complex, but since the images are always processed in the same way, numerous effects are already available in many programs, ready for use. As a user, all you have to do is define the images and select the desired effect. Effects can be used to loosen up presentations and make films more attractive. However, too many effects have a disruptive effect, and in the worst case, they can even distract from the content or make representations unrecognizable.

Other animation techniques

The animation techniques presented here are most common in practice. There are some other techniques, especially for creating 3D animation, such as: B. automatic motion sequences based on physical properties, inverse kinematics or tracking shots (Mealing, 1992). In the field of 2D animation, there are also approaches to define motion sequences using control systems or visual languages. In the past, animation effects were also created by rotating color tables. Certain color tones (e.g. blue areas of the sea) are cyclically interchanged with one another so that the impression of movement is created. Since only the color table changes, but not the image itself, this method was very popular due to the low memory and computing requirements.

Last change: 08.08.2016

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e-teaching.org (2016). Basic animation techniques. Last changed on 08/08/2016. Leibniz Institute for Knowledge Media: https://www.e-teaching.org/technik/aufbereitung/animation/grundlagen/index_html. Accessed on May 24th, 2021