31474 - Computer CAD Laboratory T-2 L

Learning outcomes

Course contents

Conventional drawing tools

Paper and standardization of the sheet of paper,. Folding the drawings. Scale of representation. Pencil and lead. Square and rule. Compass, curvilinear, mask. Parallel rules and drafting machine.

 

Computer tools

Architecture of a CAD (Computer Aided Design). Hardware: processors, random access memory (RAM), mass storage (hard disk), floppy disk, CD-ROM. Input devices: keyboard, mouse, tablet, scanner. Output devices: vectorial visualization devices and raster-scan, hard copy devices (plotters, dot matrix printer, ink-jet printer, laser-jet printer). Software: user interface, definition and processing of the model, rendering, data management, application and utility. Advantages and disadvantages of a CAD.

 

 

Raster graphics and vectorial graphics

 

Outline about the raster and the vectorial graphics especially connected to the CAD system.

 

 

Usage of a CAD system

 

The graphics primitive, simple graphics primitive, complex graphics primitive, opening layout of the drawing, data insert mode, object mode selection, modify objects commands, visualization options, pointer options, layers, blocks, blocks with symbol, dimensioning the drawings, text, running title and squaring, raster image, hatching , use of paper space, use of model space, printing the drawings, elevation drawings.

 

Basic geometrical construction

 

Bisection of a line segment, of an arc, of an angle. Perpendicular to a line from a given point: external, belonging to the line (medium point or end of line). Parallel to a given line (at a given distance or through a given point). Operation with the angles. Trisection of a right angle and of a straight angle. Division of a line in equal parts. Tangents to a circumference from an external point or from a belonging point. Internal and external tangents to two circumference. Circumference through 3 points, fillet of line and circumference with arc of given radius. Regular polygon: triangle, square, pentagon, hexagon and octagon with a given side or with circle circumscribing. Construction of a polygon with an unspecified number of side given the length of a side or the circle circumscribing. Plane curve (ellipse, parabola, hyperbole, oval, involute). Analysis and comparison of the snapping and object snapping in the CAD system.

 

Orthogonal projection method

 

Representation with orthogonal projection on two orthogonal plane of points, lines, planes. Belonging condition of a point to a line, of a line to a plane, of a point to a plane. Conditions of complanarity, incidence and parallelism for lines; condition of parallelism for planes. The third plane of projection: determination of the third projection of points, lines, planes. Orthogonal projection of plane figure and solid figure. Rule for the detection and representation of hidden and no hidden lines.

 

Real shape of plane surfaces

 

Generality. Method of spreading out flat. Spreading out flat of points, lines, segment, plane figure on plane orthogonal to principal plane of projection.

 

Primitive geometry in model space and paper space.

 

Oblique axonometric projection, orthogonal, perspective

 

Reduction factor. Unified oblique axonometric projection (cavalier; UNI4819). Orthogonal parallel perspective orthogonal axonometric. Unified isometric axonometric (UNI4819). Axonometric representation of plane surfaces, prism and pyramid; true and approximate representation of circles. Curves and revolute solids. Homography and stereography concept.

 

 

Use of CAD software to note 3D scenary, homography based.

 

 

Sections

 

Aim of sections: ideal plane of section. Plane sections of prism and pyramids. Sections of revolute solids (cylinder, cone, sphere and torus). Determination of the contour lines of the sections: generating lines method, auxiliary plane section method. Solids obtained by section plane (frustum of cone, pyramid, cylinder).

 

Use of pattern in CAD systems

 

Compenetration of solids.

 

Generality. Compenetration of prism and pyramid. Special use of auxiliary section plane. Determination of the intersecting lines of compenetrating revolute solids: generating lines method, auxiliary section plane method, auxiliary sphere method.

 

Shadow theory

Definitions, shadow of a segment, a line, a solid. Shadows and their calculation.

 

 

Dimensioning

 

General criterion. Dimensioning lines and reference line, disposal and interpretation of the dimension. Dimensioning system (in series, in parallel, overlapped dimension, combined dimension, coordinate dimension, polar coordinate dimension). Special convention dimensioning (bodies of revolution, circles, spheric surfaces, squares, chamfer and round, regularly and irregularly disposed element). Criterion of choice of the reference elements and general rules for a correct dimensioning.

 

Working principle of 3D CAD system.

Coordinate system and reference system.

• Coordinate system:
• Cartesian
• Cylindrical
• Spherical or polar
• Homogeneous
• Reference system:
• Local
• Global
• Observer
• Point of view

 

Display on screen of geometric primitive and outline on the classic algorithm.

 

Basie geometric unit

 

Visualization method of the elementary geometric entity.

Transformations:

• Translations
• Rotations
• Scale transformation
• Symmetry and mirroring

 

Rendering and animation

 

• Rendering basic concept
• Lighting
• Reflection models. Shading
• Animation control methods

 

Contour line

 

Outline on the principal system of cartographic representation. Graphic symbol used in cartography. Representation of the territory with contour line. Standard. 3D visualization and representation with altimetric sections.

Readings/Bibliography

- McMahon, Browne, CADCAM, from principles to practise, Addison-Wesley Publ.
- Mortenson, Modelli geometrici in computer graphics, McGraw-Hill.

Teaching methods

Course configuration:
- theoretical room classes;
- practical laboratory activities using CAD software and programming tools.

Assessment methods

Written and oral test. During class hours, exercises completed and corrected on site, will be considered part of written test. If all exercises will be evaluated in class hours, an average mark will replace the written test. In case of written test, that will be using computer.

Links to further information

http://diem1.ing.unibo.it/personale/liverani/teach_resources.htm

Office hours

See the website of Alfredo Liverani