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3d modeling

3D Modeling – What is it? How it is Done?

In this article we will look into what the 3D modeling is all about. We will see the subject in general, and then dig into the details and inspect the various techniques employed in the modeling process.

Concepts:

If you have seen a sculpture ever in your life, you already know quite a little about 3D Modeling. 3D Modeling is nothing but the creation of a character or a model having three dimensions (as in real world) using the techniques and tools provided by a computer software. The software we use for the purpose will be a 3D Modeling and animation tool like 3DS Max, Maya, SoftImage etc. The tool will provide a set of tools that a 3D artist can use to sculpt or model, an object in his imagination, into a 3d computer representation. This 3D model can be altered, animated or rendered into a movie in accordance to the artists need. This is what 3D modeling is, if we look it from a broad top view.

Lets dig a bit deeper:

Every 3D Model in computer representation is composed of polygons. The polygons may have three or more vertices and such hundreds or thousands or even millions of polygons may comprise a 3D Model. So is it like, a 3D artist draws each and every polygon as such? Fortunately, no! Here comes the softwares like 3DS Max and Maya to our rescue. These 3d modeling packages provide a wide variety of modeling tools that an artist can use for creating a polygonal model. The artist will usually draw the outlines that define the models shape in three dimensions, and the software will tesselate that into a polygonal mesh. All that an artist has to do is define the 3 dimensional profile of the character he has in his imagination. There are a number of modeling techniques that are widely used. Lets go through them one by one:

Primitive Modeling:

This is a very basic modeling technique and hence has several draw backs too. The software tool like 3DS Max, Maya etc provides a set of 3D primitives like spheres, boxes etc. The artist alters these shapes to suit his/her character modeling needs, using lattices, deformers etc. For example, a human head can be modeled using an altered sphere, a neck using an altered cylinder etc. This modeling technique is more suitable for building objects like houses, furniture etc rather than, for live organic modeling, since the shapes appear distinct and the blend of various body parts will not be seamless.

NURBS Modeling:

NURBS stands for Non Uniform Rational Bspline. Dont get scared by the name. In the nutshell, it is nothing but a mathematical curve, represented using a set of equations. If we see this modeling technique from an outer view, all we see is a set of simple curves that we call NURBS. How the 3d tool implemented it we dont need to care much (too much mathematics). These curves are very flexible and have control points on them which we can use to change its shape.

Suppose you want to model a human head using NURBS modeling, you will start with an outline shape and then draw a number of curves extending from one side of the profile shape to the other end, separated by spaces. These curves define the shape of the figure. These NURBS curves can be joined to form a 3D NURBS surface. The NURBS modeling has its advantages and disadvantages. It is an easy to model approach, since the NURBS curves are easy to manipulate. But this modeling technique has very limited extensibility. Suppose you want to add an extra limb to your alien creature after the modeling is complete, it will become extremely difficult, if you choose NURBS modeling.

Surface Modeling:

This is a widely adopted modeling technique used primarily for organic modeling. In this modeling technique, the 3D artist creates a spline cage profile for the 3D character. The splines intersect between each other, creating a completely closed profile of the character, unlike the NURBS technique. Once the spline cage is complete, the 3D artist can apply a surface modifier on this spline cage, which creates a 3D filling surface out of the 2D splines. This method has the advantage that it can be extended to adapt to varied requirements, during any stage of the modeling process. This offers a lot of flexibility to the artist. This technique is used widely in 3D animation software’s like 3DS Max.

Polygonal Modeling:

This is one of the very few modeling techniques that can be used for various modeling scenarios. This modeling technique is used both in organic and inorganic modeling. The basic principle behind this modeling technique is as follows. The 3D artist draws the shape of the model he wants to create using the polygon tool. Then the polygon will get subdivided and extruded, so that the model gets the 3D form. This process of subdividing and extruding continues until the whole model is completed. In this modeling technique the artist in fact creates a polygonal mesh himself. But this polygonal model will have the minimal number of polygons only, and it will be far from a smooth and perfect figure. After this stage, the artist would apply a smoothing modifier on this polygon model, which converts the model into a realistic and smooth looking character.

Sub-division Modeling:

This is a hybrid modeling technique, which inherits the merits of both NURBS modeling and Polygonal Modeling. It also offers a host of other enhancements. In sub-divisional modeling, the artist usually starts with a polygonal model itself. The polygonal model that has been already created is converted into a sub-divisional model. The sub-divisional model has control points and lattices that can be pulled and moved, to alter the original polygonal model that lies beneath. This modeling technique also permits the artist to select the level of refinement to be done in a particular area. Hence those areas requiring higher detail can be assigned with more control points and higher no: of vertices, whereas the other areas will remain with a base vertex density. This gives significant performance boost.

Conclusion:

The above discussed modeling techniques are used by the 3d artist to create a model that he has in his imagination. The model obtained through these modeling techniques will be dependent on that specific modeling technique. Such a model is converted into a pure polygonal mesh and is rigged and animated based on the requirements. During the stage called rendering, the scene which contains many such polygonal models, gets converted to a two dimensional image or a movie by the 3D animation software rendering engine.

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