3D Modeling Part 2

Modeling processes

The vast majority of 3D models today are built as textured polygonal models, because they are flexible and because computers can render them so quickly. However, polygons are planar and can only approximate curved surfaces using many polygons. NURBS modeling - NURBS Surfaces are defined by spline curves, which are influenced by weighted control points. The curve follows the points. Increasing the weight for a point will pull the curve closer to that point. NURBS are truly smooth surfaces, not approximations using small flat surfaces, and so are particularly suitable for organic modeling. Maya and Rhino 3d are the most well-known commercial software that uses NURBS natively. Splines in such cases modeling is just part of the scene creation process (this is the case, for example, with Caligari trueSpace and Realsoft 3D). Complex materials such as blowing sand, clouds, and liquid sprays are modeled with particle systems, and are a mass of 3D coordinates which have either points, polygons, texture splats, or sprites assign to them.

Scene setup

Scene setup involves arranging virtual objects, lights, cameras and other entities on a scene which will later be used to produce a still image or an animation. Lighting is an important aspect of scene setup. As is the case in real-world scene arrangement, lighting is a significant contributing factor to the resulting aesthetic and visual quality of the finished work. As such, it can be a difficult art to master. Lighting effects can contribute greatly to the mood and emotional response effected by a scene, a fact which is well-known to photographers and theatrical lighting technicians.
It is usually desirable to add color to a model’s surface in a user controlled way prior to rendering. Most 3D modeling software allows the user to color the model’s vertices, and that color is then interpolated across the model’s surface during rendering. This is often how models are colored by the modeling software while the model is being created. The most common method of adding color information to a 3D model is by applying a 2D texture image to the model’s surface through a process called texture mapping. Texture images are no different than any other digital image, but during the texture mapping process, special pieces of information are added to the model that indicate which parts of the texture image map to which parts of the 3D model’s surface. Textures allow 3D models to look significantly more detailed and realistic than they would otherwise. Other effects, beyond texturing and lighting, can be done to 3D models to add to their realism. For example, the surface normals can be tweaked to affect how they are lit, certain surfaces can have bump mapping applied and any other number of 3D rendering tricks can be applied.

3D models are often animated for some uses. They can sometimes be animated from within the 3D modeler that created them or else exported to another program. If used for animation, this phase usually makes use of a technique called “keyframing”, which facilitates creation of complicated movement in the scene. With the aid of keyframing, one needs only to choose where an object stops or changes its direction of movement, rotation, or scale, between which states in every frame are interpolated. These moments of change are known as keyframes. Often extra data is added to the model to make it easier to animate. For example, some 3D models of humans and animals have entire bone systems so they will look realistic when they move and can be manipulated via joints and bones, in a process known as skeletal animation.

Compared to 2D methods

A fully textured and lit rendering of a 3d model.

3D Photorealistic effects are often achieved without wireframe modeling and are sometimes indistinguishable in the final form. Some graphic art software includes filters that can be applied to 2D vector graphics or 2D raster graphics on transparent layers.

Advantages of wireframe 3D modeling over exclusively 2D methods include: Flexibility, ability to change angles or animate images with quicker rendering of the changes; Ease of rendering, automatic calculation and rendering photorealistic effects rather than mentally visualizing or estimating; Accurate photorealism, less chance of human error in misplacing, overdoing, or forgetting to include a visual effect.

3D model market

3CT (3D Catalog Technology) has revolutionized the 3D model market by offering quality 3D model libraries free of charge for professionals using various CAD programs. This uprising technology is gradually eroding the traditional “buy and sell” or “object for object exchange” markets.
A large market for 3D models still exists - either for individual models or large collections. Online marketplaces for 3D content allow individual artists to sell content that they have created. Often, the artists’ goal is to get additional value out of assets they have previously created for projects. By doing so, artists can earn more money out of their old content, and companies can save money by buying pre-made models instead of paying an employee to create one from scratch.