Morph target animation

Morph target animation, per-vertex animation, shape interpolation, shape keys, or blend shapes[1] is a method of 3D computer animation used together with techniques such as skeletal animation. In a morph target animation, a "deformed" version of a mesh is stored as a series of vertex positions. In each key frame of an animation, the vertices are then interpolated between these stored positions.

Sintel-face-morph
In this example from the open source project Sintel, four facial expressions have been defined as deformations of the face geometry. The mouth is then animated by morphing between these deformations. Dozens of similar controllers are used to animate the rest of the face.
Morph-puzzle
An arbitrary object deformed by morphing between defined vertex positions.

Technique

The "morph target" is a deformed version of a shape. When applied to a human face, for example, the head is first modelled with a neutral expression and a "target deformation" is then created for each other expression. When the face is being animated, the animator can then smoothly morph (or "blend") between the base shape and one or several morph targets. [2] Typical examples of morph targets used in facial animation is a smiling mouth, a closed eye, and a raised eyebrow, but the technique can also be used to morph between, for example, Dr Jekyll and Mr Hyde. Early 3D videogames, such as Quake and Crash Bandicoot use per-vertex animation for all character animations.

When used for facial animation, these morph target are often referred to as "key poses". The interpolations between key poses when an animation is being rendered, are typically small and simple transformations of movement, rotation, and scale performed by the 3D software. [1]

Not all morph target animation has to be done by actually editing vertex positions. It is also possible to take vertex positions found in skeletal animation and then use those rendered as morph target animation.

An animation composed in one 3D application suite sometimes needs to be transferred to another, as for rendering. Because different 3D applications tend to implement bones and other special effects differently, the morph target technique is sometimes used to transfer animations between 3D applications to avoid export issues.

Benefits and drawbacks

There are advantages to using morph target animation over skeletal animation. The artist has more control over the movements because they can define the individual positions of the vertices within a keyframe, rather than being constrained by skeletons. This can be useful for animating cloth, skin, and facial expressions because it can be difficult to conform those things to the bones that are required for skeletal animation.

However, there are also disadvantages. Vertex animation is usually a lot more labour-intensive than skeletal animation because every vertex position must be manually manipulated and, for this reason, the number of pre-made target morphs is typically limited. [1] Also, in methods of rendering where vertices move from position to position during in-between frames, a distortion is created that does not happen when using skeletal animation. This is described by critics of the technique as looking "shaky". On the other hand, this distortion may be part of the desired "look".

See also

References

  1. ^ a b c Liu, Chen (2006). "An Analysis of the Current and Future State of 3D Facial Animation Techniques and Systems" (PDF). pp. 12–14. Retrieved January 30, 2011.
  2. ^ Glanville, Steven (2006). "Anim8or Manual, Chapter 3 Object Editor". Anim8or. Retrieved January 30, 2011.
Computer animation

Computer animation is the process used for digitally generating animated images. The more general term computer-generated imagery (CGI) encompasses both static scenes and dynamic images, while computer animation only refers to the moving images. Modern computer animation usually uses 3D computer graphics, although 2D computer graphics are still used for stylistic, low bandwidth, and faster real-time renderings. Sometimes, the target of the animation is the computer itself, but sometimes film as well.

Computer animation is essentially a digital successor to the stop motion techniques using 3D models, and traditional animation techniques using frame-by-frame animation of 2D illustrations. Computer-generated animations are more controllable than other more physically based processes, constructing miniatures for effects shots or hiring extras for crowd scenes, and because it allows the creation of images that would not be feasible using any other technology. It can also allow a single graphic artist to produce such content without the use of actors, expensive set pieces, or props. To create the illusion of movement, an image is displayed on the computer monitor and repeatedly replaced by a new image that is similar to it, but advanced slightly in time (usually at a rate of 24, 25 or 30 frames/second). This technique is identical to how the illusion of movement is achieved with television and motion pictures.

For 3D animations, objects (models) are built on the computer monitor (modeled) and 3D figures are rigged with a virtual skeleton. For 2D figure animations, separate objects (illustrations) and separate transparent layers are used with or without that virtual skeleton. Then the limbs, eyes, mouth, clothes, etc. of the figure are moved by the animator on key frames. The differences in appearance between key frames are automatically calculated by the computer in a process known as tweening or morphing. Finally, the animation is rendered.For 3D animations, all frames must be rendered after the modeling is complete. For 2D vector animations, the rendering process is the key frame illustration process, while tweened frames are rendered as needed. For pre-recorded presentations, the rendered frames are transferred to a different format or medium, like digital video. The frames may also be rendered in real time as they are presented to the end-user audience. Low bandwidth animations transmitted via the internet (e.g. Adobe Flash, X3D) often use software on the end-users computer to render in real time as an alternative to streaming or pre-loaded high bandwidth animations.

DigiCel FlipBook

DigiCel FlipBook is 2D animation software that runs on Microsoft Windows or Mac OS X. It is intended to closely replicate the traditional animation process, very similar to the likes of TVPaint and Toon Boom Harmony.

Interactive skeleton-driven simulation

Interactive skeleton-driven simulation (or Interactive skeleton-driven dynamic deformations) is a scientific computer simulation technique used to approximate realistic physical deformations of dynamic bodies in real-time. It involves using elastic dynamics and mathematical optimizations to decide the body-shapes during motion and interaction with forces. It has various applications within realistic simulations for medicine, 3D computer animation and virtual reality.

Milkshape 3D

MilkShape 3D (MS3D) is a shareware low-polygon 3D modeling program created by Mete Ciragan. It is used mainly for compiling models for Half-Life, Blockland, The Sims 2, The Sims 3, Rock Raiders, and other sandbox video games.[citation needed] It is also used to create models for a large number of indie games, Milkshape 3D's repertoire of export capabilities has been extended considerably, due to the efforts of both its creator and the community around it, and it is now able to be used for most games today, so long as an exporter for the required format is available.

Modo (software)

Modo (stylized as MODO, originally modo) is a polygon and subdivision surface modeling, sculpting, 3D painting, animation and rendering package developed by Luxology, LLC, which is now merged with and known as Foundry. The program incorporates features such as n-gons and edge weighting, and runs on Microsoft Windows, Linux and macOS platforms.

Morphing

Morphing is a special effect in motion pictures and animations that changes (or morphs) one image or shape into another through a seamless transition. Traditionally such a depiction would be achieved through cross-fading techniques on film. Since the early 1990s, this has been replaced by computer software to create more realistic transitions.

Polygon mesh

A polygon mesh is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling. The faces usually consist of triangles (triangle mesh), quadrilaterals, or other simple convex polygons, since this simplifies rendering, but may also be composed of more general concave polygons, or polygons with holes.

The study of polygon meshes is a large sub-field of computer graphics and geometric modeling. Different representations of polygon meshes are used for different applications and goals. The variety of operations performed on meshes may include Boolean logic, smoothing, simplification, and many others. Volumetric meshes are distinct from polygon meshes in that they explicitly represent both the surface and volume of a structure, while polygon meshes only explicitly represent the surface (the volume is implicit). As polygonal meshes are extensively used in computer graphics, algorithms also exist for ray tracing, collision detection, and rigid-body dynamics of polygon meshes.

Skeletal animation

Skeletal animation is a technique in computer animation in which a character (or other articulated object) is represented in two parts: a surface representation used to draw the character (called skin or mesh) and a hierarchical set of interconnected bones (called the skeleton or rig) used to animate (pose and keyframe) the mesh. While this technique is often used to animate humans or more generally for organic modeling, it only serves to make the animation process more intuitive, and the same technique can be used to control the deformation of any object—such as a door, a spoon, a building, or a galaxy. When the animated object is more general than, for example, a humanoid character, the set of bones may not be hierarchical or interconnected, but it just represents a higher level description of the motion of the part of mesh or skin it is influencing.

The technique was introduced in 1988 by Nadia Magnenat Thalmann, Richard Laperrière, and Daniel Thalmann. This technique is used in virtually all animation systems where simplified user interfaces allows animators to control often complex algorithms and a huge amount of geometry; most notably through inverse kinematics and other "goal-oriented" techniques. In principle, however, the intention of the technique is never to imitate real anatomy or physical processes, but only to control the deformation of the mesh data.

Torque (game engine)

Torque Game Engine, or TGE, is an open-source cross-platform 3D computer game engine, developed by GarageGames and actively maintained under the current versions Torque 3D as well as Torque 2D. It was originally developed by Dynamix for the 2001 first-person shooter Tribes 2. On September 2012, GarageGames released Torque 3D as open-source software under the MIT License.Torque 3D features a world editor suite including tools for sculpting terrain and painting forests, drawing rivers and roads, as well as material, particle and decal editing. It supports the open COLLADA file format as interface to 3D digital content creation software. PhysX provides support for cloth dynamics, rigid body dynamics, destructible objects and joints, as well as fluid buoyancy simulation. Other features include a deferred lighting model and modern shader features such as dynamic lighting, normal and parallax occlusion mapping, screen space ambient occlusion, depth of field, volumetric light beam effects, lens flare/corona effects, refraction, bloom, blurring and color correction, among others. Networking functionality for multiplayer support is included as well. Build support is provided for desktop Windows, Linux, macOS and Web platforms.

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