Cinema 4D / BodyPaint 3D Program Documentation Tutorials Character Modeling Tutorial
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Basic Rules of Polygon Modeling

The following techniques can be applied to any type of polygon modeling but is particularly important for the correct creation of organic shapes/characters in order to be able to subsequently be able to deform them.

Box or Point Modeling?

These are two methods polygonal modeling. When using the "box" method a primitive (e.g., Cube, Cylinder, Sphere, etc.) or a Generator object is used as a base from which the object’s final shape is created. The "point" modeling method uses an empty Polygon object as a base and the Polygon Pen tool is used to manually create points. The "box" method is faster and is more commonly used, whereas the "point" modeling method offers more control over the wireframe model and allows for more precise modeling.

Structure of the Wireframe Model

The structure of the wireframe model should always monitored closely because it defines how the flow of the polygons and the object’s shape itself. The goal is to create a shape whose edges are as uniform as possible and subdivided correctly. If the structure or points are not aligned correctly artefacting, creasing and overlapping or intersecting polygons can result when the object is deformed or smoothed. A simple way to demonstrate this is to create a Cube, increase its Scale and Segments in the Y direction and deform it using the Bend deformer tool, as shown in the image below:

Both Cubes look identical as long as the deformer is disabled. However, as soon as the deformer is enabled in the Object Manager the Cube takes on a different appearance. The cube at the right will not be deformed to a smooth arc but will have irregularities across its surface. This is a result of the non-uniform dispersion of points and edges along the deformed surfaces.

Polygons should always have a rectangular shape and you should avoid creating elongated or twisted polygons. Irregularities most often occur along edges once the object has been smoothed. Picture your structure as a grid that covers your entire model. This grid should be as uniform as possible (uniform number and shape of polygons along adjoining parts of the model) and the polygon loops should be positioned along those regions that will later be deformed (e.g., muscle groups, creases, bending joints). Here are a few rules that should be followed when creating your model:

Triangles

Normally you should avoid using triangles because they cannot be deformed correctly. However, triangles are used in constricted regions for smoothing purposes. If you use triangles, make sure they are placed in regions that will be only slightly or not at all deformed.

Positioning of Edges and Points

Most characters are modeled on the premise that a joint skeleton (rig) will be added with which the character can be brought into motion or posed. This is why it is important to position points and edges in a manner that will enhance this movement and not impede it. This can be demonstrated using an elbow joint (consisting of a Cylinder and 2 Bones), as shown in the image below. The top cylinder is missing a row of points, which means that the elbow cannot be deformed correctly when bent, making it appear to be stretched. Furthermore, a crease is missing on the inner side resulting in a smooth transition. The bottom cylinder on the other hand has an additional row of points at the joint, which is affected by both Bones. The result is a more realistic bend of the elbow.

Smoothing

The structure of the geometry also plays a role in the smoothing of a character using Subdivision Surfaces. Take a look at the image below. The blue lines represent the original polygons; the green lines represent the polygons after being smoothed using Subdivision Surfaces; the red lines represent simple Circle splines. If a four-sided polygon is smoothed it will not produce a perfect circular shape because the edges lie too far apart. A circular shape can be more closely achieved by adding points to the four-sided polygon.

This shows how important it is to plan the subdivision of your polygon mesh. Having too many points leads to an overloaded mesh and too few points results in faulty deformations. A lot of practice is required in order to be able to correctly plan a mesh. But don’t worry - you can always remove edge loops or add subdivisions as needed in order to create a usable mesh.

Loops

Loops are also very important. They allow you to work faster and they help facilitate deformations of the model.

Changing the direction of loops can drastically change the look of the model once it is deformed. Therefore it is important to add loops in the correct order.

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