Here is my attempt at taking notes from the spoof "Stain X" movie clips and transcripts. I still find it very difficult to condense my notes into far fewer words, whilst retaining the significant meaning, so they are longer than they ought to be:
Block 3 Part 3 Activity 36
Introduction
Computers contribute hugely to the entertainment industry, including movies where CGI can be difficult to detect.
Alias produced a spoof advert “Stain X” where cockroach characters appear to perform in a real set, with their Maya CGI (Computer Generated Imagery) software.
Movies are sequences of frames changing fast enough to look as though they are moving.
Eadweard Muybridge produced movie sequence of 20 frames of a cantering horse in the early 19th century.
Disney hand-drew every single frame of their animated movies in the mid 20th century.
The role of CGI software is to provide tools allowing artists to use and manipulate 3D models and actors, then to generate the frame sequences.
Section 1
The 3D artist’s working environment is a regularly structured flat mesh that can be tweaked and twisted to create interesting objects.
CGI programs let you rotate and shade mesh object views, and each mesh intersection point can be finely manipulated along 3 axes.
A mesh is represented in a CGI program as a table of numbers, and each point on the mesh is drawn from the numbers representing its position in 3D space (somewhat similar to a graph in a spreadsheet).
Maya also has a sculpting tool amongst others that deforms the mesh as if the artist were using a brush; using this the artist can produce very complex meshes.
The finer-grained the mesh, the larger the table of numbers, and the harder the computer has to work to calculate and display it.
Texture, colour and lighting are added to meshes to make them resemble something real.
Section 2
Modern CGI programs provide artists with object templates that they can manipulate and add textures, colours and lighting, and with stock textures.
For realism, the programs can also apply ‘digital masks’ to objects, e.g., a photograph of a real face that is distorted so that it can be wrapped around a model head.
Lighting is also important for realism; a light source is just another object to be controlled and animated to a CGI program, as is fog.
Maya ensures that light automatically interacts with fog and other objects.
Section 3
One way that an object’s movement through a scene is realised is by defining a trajectory or path, that the GCI program uses to generate frame sequences.
The 3D artist can manually define a path, or more efficiently use mathematical functions such as sine waves.
The CGI program can make objects wrap around curved paths, and paths can be re-orientated independently of the objects following them to provide realistic movement.
The program can also provide other clever realism effects such as perspective, fog, dappled lighting, and automatic shadows, which it can apply to or from objects not in the field of view.
The sophisticated algorithms that CGI programs use to produce motion and lighting simulation are very computation intensive; different programs compete on the scope, efficiency, and ease of use of the algorithms.
A CGI program can also put the viewer directly into the scene, following a camera trajectory, important for giving dynamic views of animated objects.
Creating realistic experiences requires objects to interact with the scene, such as a ball bouncing across a surface.
This can be done using key-framing; specifying key positions of an object and leaving the program to generate trajectories from them (interpolation).
The artist can manually adjust interpolated trajectories to enhance realism.
Artists can also add character to objects by stretching, squeezing, and rotating them (specifying these manipulations as more key frames) further enhancing realism.
Section 4
From animation of ‘simple’ objects to animation of digital actors that behave and interact as they move through a scene, is a big step.
Most CGI programs provide pre-constructed models of articulated animals or humans called digital puppets.
The animation of the digital puppets must mimic biological components in order to look credible.
Joints can be added and moved independently of each other, then a tubular mesh added providing a surface for texture and colour.
A problem for 3d artists is unnatural mesh deformation when joints are rotated, which can be made more natural with tweaking and more CGI techniques.
The CGI program can impose relationships between joints so that when one is moved, the others also move in a natural way; only one joint then needs to be key-framed.
Objects such as a ‘balloon’ can be placed inside a limb mesh to simulate changing muscle size.
Facial animation is still a very difficult task despite all of the tools provided by CGI programs.
Digital actors need to be able to convey emotions by means of facial expressions, so eyebrows, eyelids, eyes, mouth, tongue and lips are facial features than can be manipulated.
Mouth movements can be key-framed using a ‘sync’ feature that simulates the digital actor speaking.
In each key frame, all of the facial features must be set individually.
Section 5
The character Edna’s arms are set up so that can be manipulated in a way that appears natural for an anthropomorphic cockroach.
When a locator on an arm or leg is moved, for example, the limb can be posed ready for key-framing.
The CGI program allows creation of a walk cycle using just four key frames; it interpolates between them to generate around forty frames.
This sequence can be saved as animation ‘clipart’, and repeated over time to make Edna move forwards through a scene.
For more realism, texture, a surface to walk on, lighting and shadows are added. Changing camera angle and position invokes automatic perspective.
The towel that Edna is hanging out is also a CGI object, created from a mesh with special properties that allows it to behave like cloth, and removes the need for key frames for its movement.
The four cockroach actors in the movie are created from the same wire-frame model, but have different outfits with the cloth property applied.
Scene one consists of both a CGI movie and a real movie showing the rear of terraced houses where a camera pans down from a high position.
The CGI camera must perform panning identical to the real camera, achieved using special marks place in the scenes for alignment that are removed in the final scene.
CGI software has made traditional animation techniques almost redundant, but requires a much wider range of technical skills that are combined with artists’ imagination.
Section 6
Section six is the completed Stain X example movie sequence with a seamless mixture of real scenery and digital cockroach actors moving and interacting with it, and with each other.
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