ENG 004 Lecture 6, Oct 16, 2012

Announcements

• Turn in Homework #2 now.
• Read Chapter 3
• Homework #3 will be available after class
• No office hours Thursday, Oct 18
• Guest lecturer(s) on Thursday

Topics

Use of Grids

Geometric Modeling

Coordinates

Geometric Modeling

Units of Measure

• US Customary: [in]
• International System of Units, SI (metric): [mm]

Coordinates

In practice, Cartesian coordinates are default in most CAD packages.

Also the right-handed orientation is used.

Cartesian Coordinate System

2D Coordinate Systems

Rectangular: (x, y) Polar: (r, θ)

2D Coordinate Systems

3D Coordinate Systems

Rectangular: (x, y, z) Cylindrical: (rc, θ, z) Spherical: (rs, θ, φ)

Conventions

Right handed systems are the dominant convention.

Coordinate planes

3D Coordinate Systems

Grid Examples

Rectangular Grid

Isometric Grid