3D computer animation is animation created within a digitally represented three dimensional environment in which objects or characters are constructed with spatial dimensions, positioned within a virtual scene and rendered into two dimensional images for display. A 3D object normally has geometry describing its shape, materials describing its surface properties, a virtual camera defining the viewpoint and lights or illumination systems defining how the scene is visually rendered.
Animators can change the position, rotation, scale, shape or internal structure of objects over time. Although the final image appears on a flat screen, the underlying scene can contain depth and perspective relationships that are calculated mathematically. This distinguishes 3D computer animation from conventional 2D animation while allowing the two techniques to be combined extensively.
The basic production process begins with modelling, in which digital geometry is created to represent characters, environments, props and other objects. Polygonal modelling uses vertices, edges and faces to construct surfaces, while subdivision techniques can produce smoother forms from relatively simple meshes. Other approaches include sculpting, spline based modelling and procedural generation. Once geometry exists, artists create materials and textures that determine colour, reflectivity, roughness, transparency and other surface properties. A character may require additional maps representing details such as skin variation, pores, wrinkles or surface displacement. The model and its material system together provide the visual foundation that can later be animated and rendered.
Character animation usually requires rigging and skinning. A rig is a structured system of controls and joints that allows an animator to manipulate a character efficiently. The underlying skeleton can contain joints arranged in a hierarchy, while skinning defines how the surface geometry responds when those joints move. Weighting determines how strongly different vertices are influenced by particular joints. Facial animation may use blend shapes, facial rigs, skeletal controls or combinations of methods. Animators then establish key poses and transitions, using principles such as anticipation, follow through, overlapping action, arcs, spacing and timing. Advanced productions may combine hand keyframe animation with motion capture, procedural systems and simulation.
3D animation depends heavily on camera and lighting because the virtual scene contains spatial information. A camera can be moved through the environment, rotated, zoomed or assigned a particular lens and perspective. Lighting systems can reproduce direct illumination, soft shadows, reflections, refractions, ambient effects and other optical behaviours. Rendering converts the three dimensional scene into images by calculating how geometry, materials, lights and cameras interact. Different rendering methods provide different balances of speed and physical realism. Real time rendering is particularly important for games and interactive applications, while offline rendering can allow much more computationally expensive effects in feature films and high end visualisation.
Simulation can create movement that would be difficult or inefficient to animate manually. Rigid body simulation can calculate collisions and physical movement of solid objects, while cloth simulation can approximate how fabric folds, stretches and reacts to motion. Fluid and smoke simulations can generate water, fire, clouds, vapour and other phenomena. Particle systems can represent large numbers of small elements such as dust, sparks, rain or debris. Simulation parameters must still be artistically controlled because physically plausible behaviour does not automatically produce the desired dramatic result. Animators and effects artists often combine simulation with hand keyframes, constraints and corrective adjustments to achieve a specific visual intention.
3D computer animation became increasingly important from the late twentieth century onward as computing power, software and rendering technology improved. Early computer graphics demonstrated the possibility of digitally generated three dimensional imagery, while later productions established 3D animation as a major feature film and television technique. Pixar Animation Studios played a major role in popularising fully computer animated feature films, particularly through Toy Story in 1995. Other studios and visual effects companies developed distinct pipelines and techniques. The technology has since expanded into games, virtual production, advertising, architecture, medicine, engineering, scientific visualisation and virtual reality.
3D computer animation offers major advantages in asset reuse, camera flexibility, lighting control, spatial consistency and the ability to revise scenes without redrawing every frame. Once a character, environment or prop has been constructed, it can often be reused across many shots. A camera can be repositioned after animation has begun, although changes may require subsequent adjustments. Digital models can also be rendered in different styles, ranging from physically based realism to highly stylised imagery. Limitations include substantial technical complexity, large computational requirements, specialised software and the need for expertise in modelling, rigging, animation, shading, lighting, rendering and compositing.
3D computer animation should not be defined simply as realistic animation. A 3D scene can produce highly stylised, abstract or deliberately flat looking imagery, and a 2D production can simulate depth without being genuinely three dimensional. The important distinction concerns how the visual scene is constructed and manipulated. Modern productions frequently combine 3D and 2D methods, such as rendering a three dimensional environment with a hand drawn character or applying 2D compositing over a 3D animated scene. The continuing development of real time engines, procedural generation, virtual production, physically based rendering and machine assisted tools has broadened the possibilities of 3D animation while retaining the fundamental principles of spatial modelling, transformation over time and image rendering.
