3D modeling is a fascinating field that has revolutionized the way objects are created and perceived in digital environments. From video games and movies to industrial design, this technology brings to life worlds and characters with a high level of realism. However, many still wonder what 3D modeling really entails and how its underlying structure works. This guide explores the fundamental concepts of 3D modeling and the importance of topology in creating effective models.
The Fundamentals of 3D Space: Vertices, Edges, and Faces
3D modeling is based on a three-dimensional system defined by three axes: X, Y, and Z. These axes allow the identification of the position of any point in space. A 3D model is composed of a set of points, called vertices, interconnected by lines.
Vertices
Vertices are individual points in 3D space, each having its own X, Y, and Z coordinates. When opening a 3D file, such as one in .obj format, you can observe an extensive list of these coordinates.
Edges
Edges are created by connecting two vertices. This basic component helps to define the structure of the model.
Faces (Polygons)
By joining multiple edges, surfaces called faces or polygons are formed. These can be triangles (tris), quadrilaterals (quads), or polygons with more than four sides, known as N-gons. It is important to emphasize that, internally, 3D modeling programs convert all faces into a combination of triangles. This conversion can cause issues with N-gons, especially during animation or subdivision, resulting in flickering and deformations. For this reason, 3D artists often try to avoid them.
What is Topology and its Relevance?
Topology refers to how the vertices, edges, and faces are organized to form a model. Proper topology is essential not only to ensure that the model deforms correctly during animation but also to achieve a visually appealing finish.
Edge Flow
An essential concept in topology is "edge flow," which describes how the lines (edge loops) flow across the surface of the model. For example, when modeling a human face, it is advisable for the loops to follow the shapes of the eyes and mouth to facilitate natural facial expressions. These flows are influenced by poles, which are vertices where a number of edges converge that is different from four (usually three or five). The arrangement of these poles is critical for maintaining clean and functional topology.
Beyond Polygons: Other 3D Creation Techniques
Although mesh models are the most prevalent in film and video game productions, there are other ways to represent objects in three dimensions:
Curves and NURBS
Curves use "control points" to generate smooth lines with an virtually infinite level of detail. When these curves are used to create surfaces, they become NURBS (Non-Uniform Rational B-Splines). They are ideal for industrial design, such as in cars and aircraft, where precise mathematical accuracy is required, but they are more challenging to animate, so they are often converted to polygonal meshes.
Voxels
Voxels are similar to the cubes seen in environments like Minecraft. They represent "volume pixels" and provide another perspective for constructing three-dimensional worlds.
Point Clouds
Point clouds are collections of points in space, frequently originating from 3D scanning, which are then transformed into a mesh.
Key Technical Concepts in 3D Modeling
Mastering certain technical issues can significantly impact the practice of 3D modeling:
- Manifold vs. Non-manifold Geometry: A model with manifold geometry is a "watertight" object that has no holes, where each edge strictly connects two faces. In contrast, a model with non-manifold geometry has gaps or edges that connect three or more faces, which can cause confusion in modeling software, leading to issues in 3D printing, shading, and physics.
- Subdivision Surface: This technique smooths a model by subdividing its faces into smaller parts, allowing animators to work with a low-resolution version and then apply subdivision to get a final smooth and detailed model. It is critical that the topology is good; otherwise, it may "break" upon division.
- Normals: Normals are vectors that emerge from the surface of a face, indicating which side is the "exterior." In video game environments, they are used to optimize performance; the graphics engine only renders the faces whose normals are visible to the camera, ignoring the interior faces. This is why you might see only the floating eyes and teeth of a character in certain games.
- Transformation and Spaces (World, Object, Local): Each 3D object has transformation information that includes its location (translation), rotation, and scale, which is relative and defined as follows:
- World Space: Relates the object's transformation to the center of the 3D world.
- Object Space: Relates the transformation of one object to another, such as a camera.
- Local Space: Relates the transformation to the "parent" object. If the parent is moved, the child also shifts, although the local coordinates of the child do not change.
Mastering these concepts is fundamental to entering the fascinating world of 3D modeling. Each of these elements forms part of the puzzle that allows for the creation of everything from realistic characters to imaginary worlds.
A deep understanding of 3D modeling and its topology not only enhances artistic skills but also opens up a wide range of possibilities in digital creation. For more information and explorations on this topic, feel free to keep reading on the personal blog where new entries are regularly published.
