01 Handout 2: Basic Polygon Concepts PDF

AS2209 BASIC POLYGON CONCEPTS Points (Vertices) Lines (Edges) The very basic element that i...

AS2209 BASIC POLYGON CONCEPTS Points (Vertices) Lines (Edges) The very basic element that is used to Lines can be straight or curved. A straight line make up a polygonal model is called a represents the shortest distance between two point or vertex. (2) points. Geometrically, a straight line can be considered as a point traveling in a constant direction. In graphics terminology, the line is also referred to as an edge defined by two (2) vertices. Polygons (Faces) Mesh A polygon is a closed 2D shape or figure A mesh is a geometric entity that is formed with made by connecting line segments, vertices, edges, and faces, which in turn is used typically a minimum of three (3). to approximate a 3D surface. A mesh is a Common polygonal objects that we know collection of polygons that are connected. of include triangle, rectangle, quadrilateral, pentagon, and hexagon. TRIANGULATION - TRIS, QUADS, AND N-GONS Polygons can have any number of sides; three sides make up a triangle (tri), while four sides make up a quadrilateral (quad). There are a lot of fancy names for specific polygons with more than four sides, such as the pentagon, hexagon, and so on, but in the world of 3D modeling, any polygon with more than four sides is simply referred to as an n-gon. 01 Handout 2 *Property of STI  [email protected] Page 1 of 5  AS2209 PRIMITIVES There are many ways to create polygon models. The first and most common way to do so is by using primitives. Every 3D software program has primitives. Primitives are common shapes that save time by providing a starting point for various 3D models. Primitives have parameters that can be changed and edited before the geometry itself is touched. For Blender, the easiest way to create polygon objects is from the Add tab in the 3D Viewport Editor Header, or an alternative way would be by pressing Shift + A. The window that opens already contains the most common primitives. Users can add objects such as Plane, Cube, Circle, UV Sphere, ICO Sphere, Cylinder, Cone, Torus, Grid, and Susanne, the mascot of Blender. As objects are created using primitives, a properties panel will be shown in the 3D Viewport. The parameters in this panel are used to change the dimensions, position, and rotation coordinates of the object. WORKING WITH OBJECTS There is no single way to classify all the different types of modeling currently used worldwide. Instead of focusing on a set of hard and fast rules to categorize the various modeling approaches, understanding the underlying mechanism can serve to clarify the conceptualizations. 3D Modeling is not very different from some activities we did as children such as building using blocks of wood or plastic and carving things from a block of wood or modeling clay. In a broader sense, an additive approach or subtractive approach can be considered in the modeling. The additive approach goes from smaller to larger like adding the block to wood to make a larger object, and the subtractive approach is similar to chiseling away pieces of wood from a larger block. Whether using an additive or subtractive approach, modeling involves creating or recreating the shape of an object. In polygonal modeling, the 3D scene objects are generated by putting together many flat surfaces, known as polygons or faces. Polygonal modeling involves creating 3D models using meshes, also known as polygonal meshes. In polygonal modeling, 3D objects are modeled using polygon meshes to recreate the surface that is being approximated. 01 Handout 2 *Property of STI  [email protected] Page 2 of 5  AS2209 Polygonal Mesh Operations With polygons, additional operations like extrude and bevel can be performed: Bevel o The beveling operation on polygon results in the creation of inclined surfaces. It begins similar to extrusion, and the extruded polygons are scaled down or up. Using the bevel operation can create chamfered edges and corners on objects. This creates an elegant appearance of smoothed-out edges for objects. Extrude o Extrusion refers to selecting a face from a polygonal mesh or an edge and pulling it out. Extruding a face or a polygon results in more polygons being created. Subdivide o The subdivide option is available for the edge sub-object level. It is used to subdivide the selected edges. Using this operation changes the number of cuts, smoothness, type of cut, and so on of a polygonal object. 01 Handout 2 *Property of STI  [email protected] Page 3 of 5  AS2209 Inset Faces o This operation creates new Faces inside a selected geometry. This tool takes the currently selected faces and creates an inset of them, with adjustable thickness and depth. Bridge Edge Loop o The bridge edge tool gives a way to fill loops. It works by joining a sequence of adjacent loops by adding faces between them. Loop Cut o A loop cut is a tool that splits a loop of faces by inserting a new edge loop intersecting the chosen edge. 01 Handout 2 *Property of STI  [email protected] Page 4 of 5  AS2209 Knife o The knife tool is used to interactively subdivide geometry by drawing lines of closed loops to create holes. Spin o The spin tool extrudes the selected elements, rotating around a specific point and axis. References Baechler, O. (2020). Blender 3D by Example (2nd ed.). Birmingham, UK: Packt Publishing. Blain, J. (2021). The Complete Guide to Blender Graphics Computer Modeling & Animation (6th ed.). Boca Raton, FL: CRC Press. Chandramouli, M. (2022). 3D Modeling & Animation: A Primer. Boca Raton, FL: CRC Press. Tickoo, S. (2018). Blender 2.79 for Digital Artists. Schererville, IN: CADCIM Technologies. Blender 3.2 Reference manual. Blender 3.2 Reference Manual - Blender Manual. (2022, August 24). Retrieved August 24, 2022, from https://docs.blender.org/manual/en/latest 01 Handout 2 *Property of STI  [email protected] Page 5 of 5