INTRODUCTION. Computer Graphics

Transcription

1 INTRODUCTION Computer Graphics 1

2 INTRODUCTION: THE OUTLINE I. Image Processing / Computer Graphics II. Advantages III. Representative Uses IV. Classification of Applications V. History VI. Conceptual Framework VII. Our First Assignment 2

3 I. IMAGE PROCESSING / COMPUTER GRAPHICS Image Processing: Analysis and reconstruction of existing images Sub-Areas: Image Enhancement Pattern Detection and Recognition Scene Analysis Computer Vision 3

4 I. IMAGE PROCESSING 4

5 IMAGE ENHANCEMENT Apex Sharpening of Andromeda Galaxy Image 5

6 PATTERN DETECTION AND RECOGNITION Body parts detection for people tracking using trees of Histogram of Oriented Gradient descriptors, 6

7 SCENE ANALYSIS The Vision and Mobile Robotics Laboratory, 7

8 COMPUTER VISION Software That Evaluates Facial Expressions, 8

9 I. IMAGE PROCESSING / COMPUTER GRAPHICS Computer Graphics: Synthesis of new images Overlap between the two is growing William Latham, Evolutionary Art 9

10 II. ADVANTAGES Communication between user and computer Interactive graphics Creation of abstract, synthetic objects Not confined to static images: animation User controlled dynamics 10

11 III. REPRESENTATIVE USES User Interfaces Interactive Data Plotting Office Automation / Electronic Publishing Computer-Aided Drafting and Design 11

12 III. REPRESENTATIVE USES Simulation and Animation Scientific Entertainment Art and Commerce Process Control Cartography 12

13 IV. CLASSIFICATION OF APPLICATIONS Dimensionality Kind of Picture Type of Interaction Role of the Image / Graphic Relationship between Objects and Pictures Logical Temporal 13

14 DIMENSIONALITY: 2D AND 3D 14

15 KIND OF PICTURE: LINE DRAWING / WIREFRAME Grand Designs 3D Software 15

16 KIND OF IMAGE: COLOR / GRAYSCALE 16

17 TYPE OF INTERACTION Offline Plotting Interactive Plotting User Moves Around (or within) Object Interactive Object Design 17

18 ROLE OF THE IMAGE / GRAPHIC Picture as End Product Cartography Drafting Artwork Animation Picture as Means to an End CAD/CAM 18

19 V. HISTORY Beginnings Crude Plotting Sutherland 1963 Sketchpad 19

20 V. HISTORY Output Technology Vector Display Oscilloscopes were some of the 1st computer displays Computation results used to drive the vertical and horizontal axis (X-Y) Intensity could also be controlled (Z-axis) Used mostly for line drawings Display list had to be constantly updated (except for storage tubes) Raster Display 20

21 V. HISTORY Output Technology Vector Display Raster Display Raster 21

22 V. HISTORY Input Technology Light Pens Mouse, Tablet, Touch Screen, Audio Kinect 22

23 V. HISTORY Software Device Dependent Device Independent Program Portability Programmer Portability Standards Core GKS and GKS-3D PHIGS and PHIGS+ Industry Standards (as opposed to official standards) OpenGL (SGI) Java-2D and Java-3D (Sun) DirectX (Microsoft) X-Windows (MIT/Unix/Linux) 23

24 VI. CONCEPTUAL FRAMEWORK Software Hardware Application Model/data base Application program Graphics Library Graphics System/ GPU 24

25 VI. CONCEPTUAL FRAMEWORK Application Model Application Database Property Information Created by: Application Program User Interaction 25

26 VI. CONCEPTUAL FRAMEWORK Application Program Translation of the Model to Graphics Commands Database Traversal Translation to Geometric Primitives User Interaction Handling Sampling vs. Event Driven Event Loop Model State and Screen Update vs. State, Screen and Database Update 26

27 VI. CONCEPTUAL FRAMEWORK Application Program Two Basic Paradigms: Sample-Based and Geometry-Based Sample-based graphics: discrete samples are used to describe visual information pixels can be created by digitizing images, using a sample-based painting program, etc. often some aspect of the physical world is sampled for visualization, e.g., temperature across the US example programs: Adobe Photoshop, GIMP, Adobe AfterEffects 27

28 SAMPLE-BASED GRAPHICS Images are made up of 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 Samples created directly in paint-type program, or as sampling of continuous (analog) visual materials Sample values can also be input numerically Once an image is defined as pixelarray, it can be manipulated via: Image editing Image processing 28

29 SAMPLE-BASED GRAPHICS Advantages: Once image is defined in terms of colors at (x, y) locations on grid, can change image easily by altering location or color values Pixel information from one image can be copied and pasted into another, replacing or combining with previously stored pixels Disadvantages: WYSIAYG (What You See Is All You Get): no depth information can t examine scene from different point of view at most can play with the individual pixels or groups of pixels to change colors, enhance contrast, find edges, etc. 29

30 GEOMETRY-BASED GRAPHICS Geometry-based graphics (also called scalable vector graphics or object-oriented graphics) Store mathematical descriptions, or models, of geometric elements (lines, polygons, polyhedrons ) and associated attributes (e.g., color, material properties). Images created as pixel arrays (via sampling of geometry) for viewing, but not stored as part of model. Images of many different views are generated from same model Users cannot usually work directly with individual pixels in geometry-based programs; as user manipulates geometric elements, program resamples and redisplays elements 30

31 GEOMETRY-BASED GRAPHICS MODELING VS. RENDERING Modeling Create models Apply materials to models Place models around scene Place lights in scene Place the camera Rendering Take picture with camera Both can be done with commercial software: Autodesk Maya TM,3D Studio Max TM, Blender TM, etc. Point Light Spot Light Ambient Light Directional Light 31

32 VI. CONCEPTUAL FRAMEWORK Graphics Library Graphics Subroutine Library or Package Intermediary between Application and Display Hardware Examples: OpenGL, DirectX, Windows Presentation Foundation (WPF), RenderMan Primitives (characters, lines, polygons, meshes, ) Attributes Lights Color, line style, material properties for 3D Transformations Immediate mode vs. retained mode 32

33 VI. CONCEPTUAL FRAMEWORK Graphics System / GPU Logical Display Device User Interaction Modification of Model and/or Image 33

34 OUR FIRST ASSIGNMENT 34

35 THE CODE import static com.jogamp.opengl.gl4.*; import java.nio.floatbuffer; import javax.swing.jframe; import com.jogamp.common.nio.buffers; import com.jogamp.opengl.*; import public class Code extends JFrame implements GLEventListener { private GLCanvas mycanvas; public Code() { } settitle("chapter2 - program1"); setsize(600,400); setlocation(200,200); mycanvas = new GLCanvas(); mycanvas.addgleventlistener(this); getcontentpane().add(mycanvas); setvisible(true); public void display(glautodrawable drawable) { GL4 gl = (GL4) GLContext.getCurrentGL(); float bkg[] = { 1.0f, 1.0f, 0.0f, 1.0f }; FloatBuffer bkgbuffer = Buffers.newDirectFloatBuffer(bkg); } gl.glclearbufferfv(gl_color, 0, bkgbuffer); public static void main(string[] args) { new Code(); } } public void init(glautodrawable drawable) {} public void reshape(glautodrawable drawable, int x, int y, int width, int height) {} public void dispose(glautodrawable drawable) {} 35

36 SUMMARY I. Image Processing / Computer Graphics II. Advantages III. Representative Uses IV. Classification of Applications V. History VI. Conceptual Framework VII. Our First Assignment 36