1 computer graphics week2 –creating a picture. steps for creating a picture creating a model...
TRANSCRIPT
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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
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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.
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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.
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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
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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
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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
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The Graphics Pipeline
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Object Specification
Model
TransformationScene Description
Scene DescriptionModel
TransformationView and Light Specification
Clipping and Hidden Surface Removal
Shading Image
The Graphics Pipeline
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Display TransformationImage Output
Applications of Computer Graphics
1. Display of information2. Design3. Simulation and animation4. User interfaces
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• Display of information– Maps – GIS (geographic information system)– CT (computer tomography)– MRI (magnetic resonance imaging) – PET (positron-emission tomography)– Fluid flow, molecular biology, mathematics…
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Display of Information
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Applications of Computer Graphics.
• Design– CAD (computer-aided design):
VLSI (very-large-scale integrated) circuits– Together with other tools:
architecture or interior design
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Interior Design
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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
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Applications of Computer Graphics
• User interfaces– Friendly working environment:
windows, icons, menus, pointing devices
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Interface for a painting program
Application Programmer’s Interface
17Specifications 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
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