Computer GraphicsIntroduction

Graphics: All aspects of the production of pictures (images) using a computer

Application areas:

Display of Information

Design

Simulation

User Interfaces

Basic Graphics System:

Processor

Memory

Frame buffer

Output device

Input device

Basic Graphics System:

Processor

Memory

Frame buffer

Output device

Input device

Basic Graphics System:

Processor

Memory

Frame buffer

Output device

Input device

Basic Graphics System:

Processor

Memory

Frame buffer

Output device

Input device

Basic Graphics System:

Processor

Memory

Frame buffer

Output device

Input device

Basic Graphics System:

Processor

Memory

Frame buffer

Output device

Input device

Pixels & Frame buffer

Raster: array of pixels

Pixel: picture element

Frame Buffer: memory area used to store pixel/raster data

DRAM: Dynamic random access memory

Depth: number of bits of information stored

for each pixel

Resolution: number of pixels in frame

buffer (on screen)

VRAM: Video random access memory

Processor:

- may be main CPU or special purpose processor on video card

- performs Rasterization (Scan Conversion) conversion of geometric primitives (line, circle, etc) to pixel values in frame buffer

Output devices

CRT: Cathode Ray Tube

refresh

flicker

triads

shadow mask

LCD: Liquid crystal display

CRT: Cathode Ray Tube

refresh

flicker

triads

shadow mask

Refresh

RASTER SCAN

Output devices

CRT: Cathode Ray Tube

refresh

flicker

triads

shadow mask

TRIAD

SHADOWMASK

Vector Displaysgraphics primitives are made of sequences of strokes or vectors

Raster Displaysdisplay graphics primitives in a refresh buffer in terms of the primitive’s component pixels

Vector Displaysgraphics primitives are made of sequences of strokes or vectors

IDEAL LINE DRAWING RANDOM SCAN

Raster Displaysdisplay graphics primitives in a refresh buffer in terms of the primitive’s component pixels

IDEAL LINE DRAWING RASTER SCAN

Raster Displaysdisplay graphics primitives in a refresh buffer in terms of the primitive’s component pixels

IDEAL LINE DRAWING FILLED RASTER SCAN

IMAGES:

Point: a location on an object (or in space) relative to a Reference Coordinate System

Cartesian Coordinates: 3D space, perpendicular axes, equal distance measures on each axis

Object: specified by an organized grouping of Metric and topological information

Vertices: corner points. They carry metric information -- (X,Y,Z) coordinates.

Vertex listing: list of vertex identifiers forming polygon boundary (usually a list of indices into the vertex array)

What must be specified (known)

1 - What are the objects in the scene

2 - Where are the objects in the scene

3 - Where is the viewer

4 - Where is the viewer looking

5 - What type of projection is assumed

6 - Where are the lights

7 - ....

4 - Where is the viewer looking

1 - What are the objects in the scene

2 - Where are the objects in the scene

3 - Where is the viewer

6 - Where are the lights

5 - What type of projection is assumed

Image creation:NOTE: An image is generally a 2D projection or rendering of a 3D scene

Light: visible part of the electromagnetic spectrum

Wavelength: identifies light color (350-780 nanometers)

Light sources characterized by location, nature (point or area), color, brightness

(Simplifying assumption for now -- assume monochromatic (single color) lights)

Ray tracing is a method for following the path of a photon from its origin at a light source, bouncing off the various surfaces it strikes, before it strikes the image plane.

The Pinhole Camera

Simple model for a camera.

The pinhole allows only a small number of light rays to pass through from the scene to the film.

Film

Pinhole

Computer graphics model of pinhole camera

Eye

The pinhole is replaced by the eye and the film plane moves out in front of the pinhole (eye).