1. 3-D Modeling Concepts
Part 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/box
Cylinder
Torus
Cone
Plane

3. Basic Modeling
Arcs, ellipses, circles, curves, and freehand curves are basic 2D shapes typically provided within modeling programs called SPLINES. Shapes may be combined to create complex objects.

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. Basic Modeling
Typical parameters include center point, radius, height, width, etc.
Parameters affect the size, placement, and orientation of the object.

6. Basic Modeling
Values provided automatically by the software are called the defaults.

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. 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. 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. 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. 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. 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.
Move is used to advance an object from one position to another.

13. Modeling Techniques Modifiers are used to modify an existing shape.
Examples include taper, bend, twist, smooth, and stretch.

14. 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.