Introduction and Graphics Pipeline-Advanced multimedia technology : computer graphics

Introduction and Graphics

Pipeline

Advanced Multimedia Technology: Computer Graphics

Yung-Yu Chuang

2005/12/07

with slides by Brian Curless, Zoran Popovic, Robin Chen and Doug J ames

Introduction

• Instructor: Yung-Yu Chuang ( 莊永裕 ) • E-mail: cyy@csie.ntu.edu.tw

• Office: CSIE 527 • Web:

What is Computer Graphics ?

• Definition

– the pictorial synthesis of real or imaginary objects from their computer-based models

descriptions images

descriptions Computer Graphics images Computer Vision Image Processing

OUTPUT

IN

P

U

Computer graphics

Computer graphics

modeling rendering

Applications • Movies • Interactive entertainment • Industrial design • Architecture • Culture heritage

Animation production pipeline

story text treatment storyboard

Animation production pipeline

layout animation

shading/lighting

modeling/articulation

Scan converting lines

• A scan-converted line showing intensified pixels as black circles

The basic incremental algorithm x m y B x x m B mx y_i1  _i1   ( _i   )   _i   (x_i,Round(y_i)) (x_i,y_i) (x_i+1,y_i+m) (x_i+1,Round(y_i+m)) Desired line

The basic incremental algorithm

void Line (int x0, int y0, int x1, int y1, value) { int x; float dy, dx, y, m; dy=y1-y0; dx=x1-x0; m=dy/dx; y=y0; for (x=x0; x<=x1; x++) {

WritePixel (x, (int)floor(y+0.5), value); y+=m;

} }

Filling Polygons 2 4 6 8 10 12 14 2 4 6 8 10 12 A B C D E F a b c d Scan line

Filling Polygons

Filling Polygons

1. find the intersections of the scan line with all edges of the polygon

2. sort the intersections by increasing x coordinate

3. fill in all pixels between pairs of intersections that lie interior to the polygon

Limitations of a 2X2 matrix • Scaling • Rotation • Reflection • Shearing • What do we miss?

Parallel and perspective projections

Visibility Algorithms

• Painter’s algorithm • Ray casting

• Z-buffer