1 / 29

Program 2 due 02/01

Program 2 due 02/01. Be sure to document your program program level doc your name what the program does each function describe the arguments describe what the function does document anything you may forget in a week. Indexed Color. Needed for frame buffers with a limited depth

hashim-dotson
Download Presentation

Program 2 due 02/01

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Program 2 due 02/01 • Be sure to document your program • program level doc • your name • what the program does • each function • describe the arguments • describe what the function does • document anything you may forget in a week

  2. Indexed Color • Needed for frame buffers with a limited depth • 8 bits of color = 2**8 colors = 256 colors • default is dividing bits into rbg assignments • load color map with a pallette of 256 colors • LUT

  3. Viewing • Camera and objects are specified independently. • For a 2D world - define viewing or clipping rectangle. • Objects inside will be seen. • Objects outside will not be seen. • For a 3D world - define a viewing volume. • Orthographic projection.

  4. Matrix Modes • Pipeline graphics dependent on concatenating a number of transformation matrices. Vertices Transformer Clipper Projector Rasterizer Pixels • Matrices • model-view • projection

  5. Clients and Servers • Graphics server • Workstation with raster display , keyboard, and pointing device • Provides input and output services for network • Client • OpenGL application programs

  6. Display Lists • From display processor • A special purpose computer • Host computer sent instructions to the display processor • Instructions stored in display memory as a display file or a display list • Immediate mode • Program defines a primitive • Primitive sent to server for display • No memory of primitive exists

  7. Display Lists • Retained mode graphics • Define object once • Put description in a display list • Display list stored on the server • Redisplayed by a single function call • Advantage • Reduced network traffic • Disadvantage • Memory required on the server • Creating the display list has overhead

  8. Display Lists • Creation of a display list - use glNewList, glEndList to encapsulate the list. • Each list has an int identifier which can be invoked with the command glCallList(identifier); • Save attributes with the matrix and attribute stacks (remember from 202: push onto a stack and pop off of a stack).

  9. Interaction • According to Webster’s • To act upon each other • Two way communication • GLUT toolkit for windowing • GLUT recognizes only a small subset of the events recognized by X

  10. Input • Input devices • Logical devices • From the perspective of the application program • Physical devices • Hardware and how it works

  11. Input Modes • Mode defined by the relationship between the trigger and the measuring process. • Trigger (physical input that user signals computer). • Measure (what is returned to the program). • Request mode. • Measure returned when triggered. Trigger measure request program. Process trigger process measure.

  12. Input Modes • Sample mode • Measure returned when triggered Measure sample program Process measure • Event mode • Device triggered • Event generated • Device measure placed on the event queue • Event type tied to function called CALLBACK

  13. Input Modes Trigger measure event await program. Process trigger process measure queue event. • Event mode. • Device triggered. • Event generated. • Device measure placed on the event queue. • CALLBACK registered with the windowing system. Event type tied to function called a callback.

  14. Using the Pointing Device Mouse Triggered Events • Move event • Move the mouse with the buttons depressed • Passive move event • Move the mouse without pressing a button • Mouse event • When one of the buttons is either released or pressed

  15. Specify the Mouse Callback Function • Inmain() • With glutMouseFunc(mouse_callback_func) • void mouse_callback_func(int button, int state, int x, int, y) • The callback function specifies what actions are related to the specified event

  16. Window Event • Generated when the window is resized • Redraw all the objects in the window • How to handle the aspect ratio • Do we change the sizes or attributes of the new primitives if the size of the new window is different from that of the old

  17. Keyboard Events • Generated when the mouse is in the window and one of the keys is depressed • Returns the ascii code for the key and the x and y coordinates of the mouse • void keyboard(unsigned char key, int x, imt y)

  18. Display Callback • Invoked when GLUT determines the window should be redisplayed • Upon opening it initially

  19. Idle Function • Idle callback invoked when there are no other events. • Generates graphical primitives through a display function while nothing else is happening. • Event processing happens between calls to the idle function. • Do not spend too much time in the idle function. • Idle does not actually rerender the frame. • To rerender callglutPostRedisplay();from within the idle callback.

  20. Menus • GLUT provides popup menus • glutCreateMenu(menu_callback_name); • Menu_callback_name is the name of the function. The argument to that function is the identifier passed to the callback when the entry isselected

  21. Adding a Menu glutCreateMenu (menu_callback_name); glutAddMenuEntry("quit",1); glutAttachMenu (GLUT_RIGHT_BUTTON);

  22. Adding a menu callback menu_callback_name(int id) { if (id == . . . }

  23. Animation • Double buffering eliminates flicker.

  24. Callback Advice From the Creator of GLUT, Mark Kilgard • Don’t change state that will affect the way a window will be drawn a display callback. • If you need to redisplay a window, instead of rendering in whatever callback you happen to be in, call glutPostRedisplay. • If you use an idle callback to control animation, use a visibility callback to determine when the window is fully obscured or iconified.

  25. More Callback Advice • The backspace, Esc, and Del keys generate ASCII characters, so detect key presses for these keys using the glutKeyboardFunc callback.

  26. Design of InteractivePrograms • A smooth display (no flicker or artifacts of the refresh process) • A variety of interactive devices on the display • A variety of methods for entering and displaying information • An easy to use interface that does not require substantial effort to learn • Feedback to the user • Tolerance for user errors • A design incorporation for consideration of both the visual and motor properties of the human

  27. Limitations of Geometric Rendering • Designing widgets • example of popup menu • refreshing the display where the menu was • no primitives but uses scan line image data • operations described in terms of the frame buffer or in terms of bit-block transferoperation

  28. Limitations of GeometricRendering • Rubberbanding • a technique for displaying line segments in a changing manner. • Endpoint is selected • Before second endpoint is selected a line segment is drawn automatically to where the present position of the mouse is • As the mouse moves the old segment must be erased and a new one drawn.

  29. Homework • Read chapter 4 • Program 2 due 02/01/05

More Related