Objectives. Topic 8: Input, Interaction, & Introduction to callbacks. Input Devices. Project Sketchpad. Introduce the basic input devices

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1 Tpic 8 Input, Interactin, & Intr. t Callbacks Tpic 8: Input, Interactin, & Intrductin t callbacks Tpic 8 Input, Interactin, & Intr. t Callbacks Objectives Intrduce the basic input devices Physical Devices Lgical Devices Input Mdes Event-driven input Prgramming event input with GLUT An intrductin t callbacks CITS 3003 Graphics & Animatin Slides: E. Angel and D. Shreiner: Interactive Cmputer Graphics 6E Addisn-Wesley Tpic 8 Input, Interactin, & Intr. t Callbacks Prject Sketchpad Ivan Sutherland (MIT 1963) established the basic interactive paradigm that characterizes interactive cmputer graphics: User sees an bject n the display User pints t (picks) the bject with an input device (light pen, muse, trackball) Object changes (mves, rtates, mrphs) Repeat 3 Tpic 8 Input, Interactin, & Intr. t Callbacks Input Devices User inputs cntrl the prgram thrugh input devices Input devices can be viewed as Physical devices: described by their physical prperties, e.g., muse, keybard, trackball, etc. Lgical devices: characterized by hw they influence the applicatin prgram, e.g., what is returned t the prgram via the API An x, y psitin n the screen? An bject identifier fr a menu item chsen? Bth are perfrmed by the same physical device (the muse, in this case) but what is returned t the prgram is different. 1

Devices Cnsider the C and C++ cde C++: cin >> x; C: scanf( %d, &x); What is the input physical device?

int) is returned t the prgram regardless f the physical device 6 t Callbacks Lgical Input Devices (cnt.

cal input: Lcatr: return a psitin, e.g., clicked at by a muse pinter Chice: return ne f n discrete items, e.g., a menu item String: return strings f characters, e.

OpenGL and GLUT prvide functins t handle all these 7 t Callbacks Incremental (Relative) Devices Devices such as

return incremental inputs (r velcities) t the perating system Must integrate these inputs t btain an abslute

2 Tpic 8 Input, Interactin, & Intr. t Callbacks Physical Devices muse trackball light pen data tablet jy stick space ball 5 Tpic 8 Input, Interactin, & Intr. t Callbacks Lgical Input Devices Cnsider the C and C++ cde C++: cin >> x; C: scanf( %d, &x); What is the input physical device? Can t tell frm the cde Culd be keybard, file, utput frm anther prgram The cde prvides lgical input A number (an int) is returned t the prgram regardless f the physical device 6 Tpic 8 Input, Interactin, & Intr. t Callbacks Lgical Input Devices (cnt.) Older APIs (GKS, PHIGS, nt OpenGL) defined six specific types f lgical input: Lcatr: return a psitin, e.g., clicked at by a muse pinter Chice: return ne f n discrete items, e.g., a menu item String: return strings f characters, e.g., via key presses Strke: return array f psitins Valuatr: return flating pint number Pick: return ID f an bject OpenGL and GLUT prvide functins t handle all these 7 Tpic 8 Input, Interactin, & Intr. t Callbacks Incremental (Relative) Devices Devices such as the data tablet return a psitin directly t the perating system Devices such as the muse, trackball, and jy stick return incremental inputs (r velcities) t the perating system Must integrate these inputs t btain an abslute psitin Rtatin f cylinders in muse Rll f trackball Difficult t btain abslute psitin Can get variable sensitivity 8 2

3 Tpic 8 Input, Interactin, & Intr. t Callbacks Tpic 8 Input, Interactin, & Intr. t Callbacks Input Mdes Input Mdes (cnt.) Input devices cntain a trigger which can be used t send a signal t the perating system Buttn n muse Pressing r releasing a key When triggered, input devices return infrmatin (their measure) t the system Muse returns psitin infrmatin Keybard returns ASCII cde 9 Input mdes cncern hw and when input is btained There are tw types f input mdes: Request mde Event mde 10 Tpic 8 Input, Interactin, & Intr. t Callbacks Tpic 8 Input, Interactin, & Intr. t Callbacks Request Mde Event Mde Fr request mde input, the input value is prvided t prgram nly when user triggers the device A typical example is keybard input: The applicatin prgram request a keybard input frm the user The user can type, erase (backspace), crrect. The applicatin prgram hangs there until the enter (return) key (the trigger) is depressed Request mde is nt suitable fr prgrams that need t interact with the user. Mst systems have mre than ne input device, each f which can be triggered at an arbitrary time by a user

4 Tpic 8 Input, Interactin, & Intr. t Callbacks Event Mde (cnt.) In event mde input, the prgram specifies a number f input events that are f interest. The prgram gets int an event handling lp t deal with the events when they ccur Each trigger generates an event whse measure is put in an event queue which can be examined by the user prgram 13 Tpic 8 Input, Interactin, & Intr. t Callbacks Event Types in event mde input Windw event: resize, expse, icnify Muse event: click ne r mre buttns Mtin event: this refers t the muse mve event (when the cursr is inside the windw f the applicatin prgram) Keybard: press r release a key Idle: nn-event Define what shuld be dne if n ther event is in the event queue 14 Tpic 8 Input, Interactin, & Intr. t Callbacks Callbacks Tpic 8 Input, Interactin, & Intr. t Callbacks GLUT callbacks We can prgram t handle event mde input We can define a callback functin fr each type f event that the graphics system recgnizes This user-supplied functin is executed when the event ccurs GLUT example: glutmusefunc(mymuse) muse callback functin 15 GLUT recgnizes a subset f the events recgnized by any particular windw system (Windws, X, Macintsh) glutdisplayfunc glutmusefunc glutreshapefunc glutkeybardfunc glutidlefunc glutmtinfunc glutpassivemtinfunc 16 4

5 Tpic 8 Input, Interactin, & Intr. t Callbacks Tpic 8 Input, Interactin, & Intr. t Callbacks GLUT Event Lp The display callback Recall that the last line in main.c fr a prgram using GLUT must be glutmainlp(); which puts the prgram in an infinite event lp In each pass thrugh the event lp, GLUT 1. lks at the events in the queue 2. fr each event in the queue, GLUT executes the apprpriate callback functin if ne is defined 3. if n callback is defined fr the event, the event is ignred 17 The display callback is executed whenever GLUT determines that the windw shuld be refreshed, fr example When the windw is first pened When the windw is reshaped When a windw is expsed When the user prgram decides it wants t change the display In main() glutdisplayfunc(mydisplay) identifies the functin t be executed Every GLUT prgram must have a display callback 18 Tpic 8 Input, Interactin, & Intr. t Callbacks Tpic 8 Input, Interactin, & Intr. t Callbacks Psting redisplays References Many events may invke the display callback functin Can lead t multiple executins f the display callback n a single pass thrugh the event lp We can avid this prblem by instead using glutpstredisplay(); which sets a flag. GLUT checks t see if the flag is set at the end f the event lp If set then the display callback functin is executed Interactive Cmputer Graphics A Tp-Dwn Apprach with Shader-Based OpenGL by Edward Angel and Dave Shreiner, 6 th Ed, 2012 Sec Input Devices, Physical Input Devices, Lgical Devices, Input Mdes Sec. 2.1 The Sierpinski Gasket; immediate mde graphics vs retained mde graphics C++ cde in the Chapter02 t Chapter04 flders 19 Angel and Shreiner: Interactive Cmputer Graphics6E Addisn-Wesley

Lecture 10: Input, Interaction & callbacks. CITS 3003 Graphics & Animation

Lecture 10: Input, Interaction & callbacks CITS 3003 Graphics & Animation Slides: E. Angel and D. Shreiner: Interactive Computer Graphics 6E Addison-Wesley 2012 Objectives Introduce the basic input devices