MR.E.S.AGRAWAL SGGSIE&T, NANDED CAD Software and Hardware

ICG (Interactive Computer Graphics) ICG denotes a user oriented system. User CRT ICG magnifies the power of designer. SGGS Institute of engineering and Technology Nanded

CAD Software/Graphics software(GS) Set of programs Rules for development of GS: 1. Simplicity 2. Consistency 3. Completeness 4. Robustness 5. Performance 6. Economy SGGS Institute of engineering and Technology Nanded

Design workstation Configuration Application Database Application Program Graphics Package Graphics Terminal I/P Devices SGGS Institute of engineering and Technology Nanded

Functions of GS Generation of Graphics element Transformations Display control and windowing function Segmenting function User input functions SGGS Institute of engineering and Technology Nanded

Generation of Graphics element Graphic elements Primitives SGGS Institute of engineering and Technology Nanded

Transformations Scaling Translation Rotation Reflection SGGS Institute of engineering and Technology Nanded

Display control and windowing function Visualization Windowing Hidden line removal SGGS Institute of engineering and Technology Nanded

Segmenting function Segment Storage type CRT SGGS Institute of engineering and Technology Nanded

User input functions To enter commands User-friendly SGGS Institute of engineering and Technology Nanded

Design workstation Hardware Secondary storage O/P Devices CPU Input Devices Graphics Terminal SGGS Institute of engineering and Technology Nanded

Design workstation System Interface Functions  Interface with CPU  Steady Graphic Image  Provide digital description of the graphic image  Translate computer commands  Communication SGGS Institute of engineering and Technology Nanded

Graphics Terminal (GT) GT is an important component of CAD providing a window through which the communication with the computer can be realized. Graphics terminals are classified as 1. CRT 2. Flat Screen SGGS Institute of engineering and Technology Nanded

Graphics Terminal (GT) Two basic image generation Techniques. 1) Stroke Writing Random positioning Line drawing Vector writing  Uses an electron beam which operates like pencil.  The image is constructed out of a sequence of straight line segment. SGGS Institute of engineering and Technology Nanded

Stroke Writing Smooth curves can be created. SGGS Institute of engineering and Technology Nanded

Raster Scan The viewing screen is divided into a large no of discrete phosphor elements. Matrix of pixels constitute a raster. 256X256, 1024X1024. SGGS Institute of engineering and Technology Nanded

Raster Scan Each pixel on screen can be made to glow with a different brightness. Color screen provide for the pixels to have different color as well as brightness. SGGS Institute of engineering and Technology Nanded

Raster Scan The electron beam creates image by sweeping along horizontal line. Sweeping is from left to right. Pixels are energized during sweep. When sweep on one line is completed, the electron beam moves to next line below. SGGS Institute of engineering and Technology Nanded

Raster Scan After sweeping entire screen the process is repeated. Rate of entire scan of screen is 30 to 60 scan per sec. SGGS Institute of engineering and Technology Nanded

Graphics Terminal 1. Direct Beam Refresh 2. Direct View storage tube (DVST) 3. Raster scan (Digital TV) SGGS Institute of engineering and Technology Nanded

Direct Beam Refresh Uses stroke writing approach Refresh Easy to provide animation SGGS Institute of engineering and Technology Nanded

Direct View storage tube (DVST) Stroke writing approach Storage tube Flicker free No Trim Low cost SGGS Institute of engineering and Technology Nanded

Raster scan (Digital TV) Uses Raster Scan Approach Frame/Refresh Buffer High Cost SGGS Institute of engineering and Technology Nanded

Input Devices 1. Cursor control devices 2. Digitizers 3. Alphanumeric and other key board terminals Graphical interaction with System SGGS Institute of engineering and Technology Nanded

Cursor control devices Cursor normally takes the bright spot on CRT 1. Thumbwheel 2. Direction Key/Key board Terminal 3. Joysticks 4. Tracker Ball 5. Light Pen 6. Electronic tablet SGGS Institute of engineering and Technology Nanded

Plotters and O/P Devices Pen Plotters Hard copy Unit Electrostatic Plotters Computer output to micro film units SGGS Institute of engineering and Technology Nanded