Post on 01-Jan-2016
description
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).