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# 3 d modeling part 2

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### 3 d modeling part 2

1. 1. 3-D Modeling Concepts V106.02 part 2
2. 2. Basic Modeling All 3D modeling programs contain certain basic geometric shapes that can be combined with or subtracted from other shapes to form more complex objects. Some programs contain more objects than others, but a sample list of basic primitives includes:  Sphere  Cube or box  Cylinder  Torus  Cone  Plane
3. 3. Basic Modeling Arcs, ellipses, circles, curves, and freehand curves are basic 2D shapes typically provided within modeling programs. Shapes may be combined to create complex objects. Polygons are plane figures made with three or more straight sides (curves). Regular polygons have equal length sides and equal angles.
4. 4. Basic Modeling Splines are curves or polygons that are composed of segments that can be manipulated by control points placed along the curve. Control points may be made “active” and then dragged using a handle attached to the point.
5. 5. Basic Modeling Some programs require the user to define parameters of the primitive prior to importing it into the scene; others will bring in a “standard” sized object and place it in a selected position. Typical parameters include center point, radius, height, width, etc.
6. 6. Basic Modeling Parameters affect the size, placement, and orientation of the object. Values provided automatically by the software are called the defaults. A typical default would be to bring in an object oriented in a certain direction with respect to a construction plane.
7. 7. Modeling Techniques Boolean tools or operations are used to create objects by combining, subtracting, or determining the common intersections of various objects such as primitives. Union or Addition (+ or ∪) is used to combine objects together into one new object. Subtract or Difference (−) is used to remove part or all of an object where objects overlay each other. Intersection (* or ∩) is used to calculate the overlapping volumes of objects so that the overlap becomes the object. Named for the British mathematician George Boole.
8. 8. Modeling Techniques Extrusion, sweeping, or lofting allows you to create a 2D shape and then extend it along a path or curve to form a 3D object. The 2D shape may be open (curves that do not connect back onto the beginning or closed (lines connect back onto the beginning).
9. 9. Modeling Techniques A variation of sweeping is lofting, where a series of curves (open or closed) is lofted or spaced parallel to each other, and then a surface is generated that connects the contours. Lofting may also be done using a profile shape and a curve along which the profile is lofted. An example of where lofting is used would be for modeling boat hulls and terrains.
10. 10. Modeling Techniques Revolve or lathe operations allow the user to create a 2D shape and then revolve it around an axis. Lathe operations emulate the lathe found in manufacturing shops. A lathe is a tool used to rotate and shape material by bringing cutting tools against the material while it spins. The revolution may be a full 360 degrees or any smaller angle. Lathe operations are often used to model objects such as bowls, bottles, and dishes.
11. 11. Modeling Techniques Transformations or Transforms are actions that scale, rotate, and move objects Scale changes the size or proportions of an object along one or more axes.
12. 12. Modeling Techniques Rotate refers to tilting or changing the direction that an object is facing. Rotation is usually assigned to a particular axis. For example, the object might be rotated along its X-axis. Most programs assign a default location for rotational axes. This location (pivot point) may need to be relocated to create to the desired movement. Rotation is usually specified using degrees relative to a beginning point.
13. 13. Modeling Techniques Move is used to advance an object from one position to another. Linear distance along the X-, Y-, or Z-axis is used to measure movement. Movement may be constrained by a snap or grid setting. Snap allows the object to be moved only at set intervals of distance. Movement can also be restricted to a grid so that the object jumps from grid line to grid line.
14. 14. Modeling Techniques Deformations are used to modify an existing shape. Selected vertices, control points, polygon faces, or cross sections of an object may be used to control and influence the deformation process. Deformation tools emulate the process of working a piece of clay. Examples include taper, bend, twist, smooth, and stretch.
15. 15. Modeling Techniques Copy or Clone tools allow selected objects to be reproduced in their exact size and form. Mirror tools allow selected shapes to be copied or flipped about a defined center.
16. 16. END PART 2