Computer 3D Modeling, Displaying, and Rendering in Creating Objects

Bruvel's computer system allows him to use computer 3D modeling to give form to his ideas. Computer 3D modeling involves using the computer as a tool to create 3D forms in a digital medium. The objects can be viewed from any perspective and rendered with surface qualities for display on a computer monitor screen.

The characteristics of the program allow him as an artist to: (1) construct models with tools and methods, and alter or transform them; (2) establish a viewplane; and (3) render surface qualities and lighting. These have been described in general terms for artists and designers by Judson and Rosebush (1986). The technical tools and methods more specific to Maya 5.0 software used by Bruvel for his computer systems have been profiled by John Kundert-Gibbs and Peter Lee (2001).

Constructing Models with Tools

In computer graphics, the computer program permits Bruvel to create what are called "objects"--or points connected by line vectors-- modeled in the computer's memory. Each object is composed as a collection of points. The points exist in the computer's memory as a series of numbers, converted by the computer into a computer code of binary digits ("bits") of 0s and 1s, in 32-bit sequences. The points are assigned a location on a Cartesian Coordinate system that hypothetically exists in space and time, defined by x,y,z axes: "x" for height, "y" for width, and "z" for depth. A model for a three-dimensional (3D) form therefore exists as a collection of points on the x,y,z axes. Any 3D model for a sculpture created in virtual space with virtual material will be given designated point locations that establish the dimension of its height (x), length (y), and depth (z).

Because each model Bruvel constructs is converted by the computer as a collection of points with numerical locations existing on these axes, the points can be modified or repositioned at any stage of the creation process.

All such objects modeled this way are called virtual objects because until output or produced onto a tangible medium such as paper, film, or videotape, the images of objects exist only as points retrained as data in the computer memory by virtue of the program instructions, conceptual digital data of 0s and 1s, and the artist's decision.

Modeling Methods: There are many 3D computer modeling methods that Bruvel can use to construct a 2D shape or 3D form. Only two construction methods that Bruvel used to construct "The Passage" will briefly be described here: (1) Modeling with Primitives; and (2) Modeling with Polygons and Subdivision Surfaces. They will be described in greater detail in a later section.

Modeling Tools: All models created by Bruvel are constructed using various modeling tools that are standard options in computer graphics that can be used to construct 3D forms and objects. These modeling tools permit Bruvel to perform changes on any virtual object he creates with a computer. The most common one he uses involve modeling tools that permit geometric transformations applied to the data set of points that describe a 3D object. Transformations are basic operations founded upon mathematical procedures called geometric transformations and deformations, and other similar mathematical operations. They permit Bruvel to manipulate the mathematical constructions and distributions of the points which form the models of the 2D shapes and 3D forms he has created. Their mathematical basis remains invisible to Bruvel, the artist, but he is aware they are there, at work, embedded in the program.

The four primitive computer graphics transformations that Bruvel can apply to any shape or form he creates, include: translate, size, rotate and shear:

• Translation involves moving the position of an object.
  
• Sizing means reducing or enlarging an object.
  
• Rotation permits an object to be pivoted around an axis.
  
• Shearing displaces points relative to a point of origin.

Bruvel can also choose inverse transformations, concatenation of transformation (combination of two or more primitive transformations); and animation transformations (moving whole collections of points that form an object, through space, in a series of movements or events that appear as a pathway of motion or sequence of positions across time).

Establishing Perspective, Displaying a View

Bruvel's program permits him to model objects in real time. This means that as he creates his shapes and forms, he can watch the changes he has instructed the computer to initiate, transform them. This permits him to see how the solidly modeled object created as a 3D form in a hypothetical 3D space, can be viewed when scaled in size, or shifted and rotated in position, and displayed on a computer monitor screen.

Rendering Surface Qualities and Lighting

Bruvel's 3D forms as they are being modeled usually appear as geometric polygon facets or wireframe forms displayed on the computer screen. Once his 3D forms are completed, then Bruvel can give the computer specific instructions so that it can render the surface qualities and lighting of the objects and environment of the virtual world as they will be displayed in appearance on the monitor screen. The computer can be directed to render the external view or surface appearance of things in different ways. To these surfaces Bruvel can assign attributes such as color, luminescence, transparency, pattern, luster, or texture.

The Creative Process: Two Computer 3D Modeling Methods Used to Give Form to the Initial Idea for "The Passage"

Let us consider the two construction methods that Bruvel utilized to construct "The Passage". As noted, for "The Passage" he used basically two computer 3D modeling methods: (1) Modeling with Primitives; and (2) Modeling with Polygons and Subdivision Surfaces:

1. Modeling with Primitives: This involves modeling with primitive lines, 2D shapes or 3D forms already provided by the computer program as options Bruvel can use and begin to create forms with. From these he can extract more complex forms.

Most computer graphics systems come complete with a set of what are called "primitive functions". This includes providing primitive 2D shapes and 3D forms, as well as functions that can be used to construct and manipulated basic geometric figures. In 3D solids modeling, the building blocks are 3D primitives consisting of a sphere, cube, cylinder, cone, torus, dodecahedron, and planes

The computer modeling tools listed earlier permit Bruvel to manipulate the primitives in various ways to produce more complex 3D forms and surfaces. He can control the size, position, and shape of these objects with simple commands. He can combine one object made from a primitive solid model to another.

In constructive modeling, the final model of a 3D form is displayed as a mesh of points connected by straight or curved lines. The final contours of the form are displayed by the computer as a mesh of polygon-shaped facets.

2. Modeling with Polygons and Subdivision Surfaces

This involves constructing a form from polygons and subdivision surfaces.

Bruvel can first model an object by establishing points as its boundaries, then directing the computer to connect the points as segments or vectors. These connections may consist of line segments to model a hard-edged geometric form.

Or, these connections may consist of curves, such as Bezier, B-spline, or Non-Uniform Rational B-Spline (NURBS) curves used to model an organic rounded form. The resulting object displayed on screen appears as a mesh of polygons.

Bruvel also can use a subdivison method to sudivide the surfaces of a polygonal mesh. Using this construction method, Bruvel constructs polygonal surfaces. He can select a section of that surface and subdivide it into even smaller polygonal facets to create more complex forms. He can establish a point beyond the polygonal surface (along a z axis), select an area on the polygonal surface, and then direct the computer to extend that part of the surface into "z space"--or to extrude its form to meet the new point location.

The advantage to this modeling method is that any point on the surface can be selected for further manipulation. By successively subdividing a surface over several stages, a polygonal hard-edged form eventually can be refined to look smoothly rounded. This method is particularly good for modeling complex organic forms like the human head.

Hyperlinks:

For more information on the 3D modeling method of subdivision surfaces, see:

http://enphilistor.users4.50megs.com/sss.htm
and
http://www.gamasutra.com/features/20000411/sharp_01.htm

For more information on NURBS see:

http://webopedia.internet.com/TERM/N/NURBS.html

Combining Methods

Bruvel uses both of these modeling methods. They both can be compared by analogy to traditional sculpture methods in one way because they involve using additive processes for constructing forms in three dimensions. But they are different from traditional sculpture methods because he is working with virtual material in virtual 3D space, rather than with concrete real world materials. Here is how he described this analogy in his own words, in an interview conducted in 1999 for a book about his work:

H: What steps do you take to create a computer graphics model of a 3D form?

B: The easiest way is to start with a primitive--where you would basically create from a basic line, shape, or form. You can start with a line, or a curve, and map or build something around them. Or, you can start with a sphere....then you can add other primitive forms to it, or subtract from its form. For example, let's say I start with a primitive--a line. Next, you use it to create a shape. Both are defined as coordinate points on the x,y axes. Then, you place it into a 3D depth space; you mark the points where you will extend the shape along the z axis into z-space to create depth. This is my path. I tell the computer to extend the shape into z-space along that path; to extrude it. The moment I tell the computer to connect the points from here to there, or to extrude the shape along the z path, then the 2D shape becomes a 3D form. I have the model of a 3D form in 3D space.

H: Like squeezing clay through a path, as though extruded through a play dough machine?

B: Yes. Then I can transform it in a variety of ways. For example, I can scale it [by changing its size]. I can create a hierarchy of different points—I can pick and choose [or specify a position that incorporates a sequence of two or more individual primitive transformations] and establish them at different point locations in z-space; then I can use extrusion to connect them or extrude them from my original form to this new location in z-space to make a more complex form. I can do all kind of things. I can take a deformer and generate a form that would be different from the form of origin.

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