What is Geometric Modeling?

}What is a model?

}Captures salient features (data, behavior) of thing/phenomenon being modeled

}data includes geometry, appearance, attributes…

}note similarity to OOP ideas

}Real: some geometry inherent

}physical (e.g., actual object such as a chair)

}non-physical (e.g., mathematical function, weather data)

}Abstract: no inherent geometry, but for visualization

}organizational (e.g., company org. chart)

}quantitative (e.g., graph of stock market)

 

Geometric Modeling

 

Vector Graphics

Vector Graphics- Geometry-based Graphics - object-oriented graphics

}Geometry is created along with various appearance attributes, and is then sampled for visualization (via rendering).

    }examples of 2D apps: Adobe Illustrator™, Adobe Freehand™, Corel CorelDRAW™

 }examples of 3D apps: Autodesk’s AutoCAD2010™, Autodesk’s (formerly Alias|Wavefront’s) Maya™, Autodesk’s) 3D Studio Max™ 

}Geometry-based graphics applications store mathematical descriptions, or “models,” of geometric elements (lines, polygons, polyhedrons…) and associated attributes (e.g., color, material properties). Elements are primitive geometric shapes, primitives for short.

Pixels

}Images are made up for grid of discrete pixels, for 2D “picture elements”

}Pixels are point locations with associated sample values, usually of light intensities/colors, transparency, and other control information

}When we sample an image, we sample the point location along the continuous signal and we cannot treat the pixels as little circles or squares.

 

SketchPad

SketchPad (1963) was a revolutionary program which is considered the ancestor to today's Computer Aided Design (CAD) software, as well as a huge step forward in computer graphics. SketchPad was developed by Ivan Sutherland at MIT.

DEMO: SketchPad


A Man-Machine Graphical Communication System:by Ivan Sutherland

The Sketchpad system uses drawing as a novel communication medium for a computer. The system contains input, output, and computation programs which enable it to interpret information drawn directly on a computer display. Sketchpad has shown the most usefulness as an aid to the understanding of processes, such as the motion of linkages, which can be described with pictures. Sketchpad also makes it easy to draw highly repetitive or highly accurate drawings and to change drawings previously drawn with it…

         

What is Interactive Computer Graphics?

}User controls contents, structure, and appearance of objects and their displayed images via rapid visual feedback.

}Basic components of an interactive graphics system

}input (e.g., mouse, tablet and stylus, multi-touch…)

}processing (and storage)

}display/output (e.g., screen, paper-based printer, video recorder…)

}First truly interactive graphics system, Sketchpad, pioneered at MIT by Ivan Sutherland for his 1963 Ph.D. thesis

Basics-1

Computer graphics
                  Is all these  – " a consciously managed and documented technology directed toward communicating information accurately and descriptively.”

                   Its is Not----It is not a machine. It is not a computer, nor a group of computer programs. It is not the know-how of a graphic designer, a programmer, a writer, a motion picture specialist, or a reproduction specialist