1 Computer Graphics Week2 –Creating a Picture

Steps for creating a picture Creating a model Perform necessary transformation Lighting and rendering the object The goal is the creation of an image by writing a program instead of taking a picture with a camera There exists an analogy between writing graphical programs and taking pictures by a camera 2

Pixels Pixel or “Picture element” is the simplest element in computer graphics Single location on the computer screen or printout Value of each pixel is the range from white to black or range of intensities of red, green, blue (RGB) colors. 3

Frame buffers The pixels of an image are organized into two dimensional grid – frame buffer Multiple frame buffers can be stored in computer memory Double buffering – first image is drawn into frame buffer and sent to display. While the user is looking on the display, the next picture is drawing to the second buffer. 4

Windows Image don’t fill the entire screen but is drawn into a window Pixels are adressed within the window based on their location Relative position of each pixel enables moving the window and change its size 5

Realistic images Calculating pixel values to create impression of a realistic picture Simulation of objects from the real word Approximation of physical properties of objects Limitations given by computing time and memory space 6

The Graphics Pipeline Modeling – creates an internal representation of the objects in the scene Rendering – converts the screen description into image Display – shows the image on the output device 7

The Graphics Pipeline 8 Object Specification Model Transformation Scene Description Model Transformation View and Light Specification Clipping and Hidden Surface Removal Shading Image

The Graphics Pipeline 9 Display Transformation Image Output

Applications of Computer Graphics 1.Display of information 2.Design 3.Simulation and animation 4.User interfaces 10

Display of information – Maps – GIS (geographic information system) – CT (computer tomography) – MRI (magnetic resonance imaging) – PET (positron-emission tomography) – Fluid flow, molecular biology, mathematics… 11

Display of Information 12

Applications of Computer Graphics. Design – CAD (computer-aided design): VLSI (very-large-scale integrated) circuits – Together with other tools: architecture or interior design 13

Interior Design 14

Applications of Computer Graphics Simulation and animation – Flight simulation – pilot training – Games and educational software – Benefits: Less cost Less danger, e.g. combination with the VR (virtual reality) techniques can help surgical interns and astronauts 15

Applications of Computer Graphics User interfaces – Friendly working environment: windows, icons, menus, pointing devices 16 Interface for a painting program

Application Programmer’s Interface 17 Specifications of the functions in the graphics library The OpenGL graphics system is an Application Programming Interface (API) to graphics hardware.

Three-dimensional APIs Objects Viewers Light sources Material properties 18