GLUT and GLVU

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GLUT and GLVU

• Andy Wilson
• September 22, 1999

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Outline

• Introduction
• GLUT
• GLVU
• Where to learn more
• Questions and Answers

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Introduction Motivation

• So you want to use OpenGL?
• Low-level commands
• Manage rendering state
• Render primitives
• The windowing system is in your way
• No world management available

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Introduction GLUT

• GLUT simple interface to window system
• User functions handle window events
• mouse, keyboard, resize, expose
• Simple pop-up menus
• A few simple shapes (sphere, cone, teapot)
• No concept of world or camera management
• You reinvent the wheel a lot.

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Introduction GLVU

• GLVU object and camera management
• Several different model formats
• Renderable objects
• Easily extensible
• Several modules available or under development -
  IBR, tracking, large models, LOD...

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Outline

• Introduction
• GLUT
• GLVU
• Where to learn more
• Questions and Answers

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GLUT System Overview
User Callbacks (Display, Idle, Keyboard, Mouse,
Resize, )
GLUT
Window System
Events (Mouse, Keyboard, Window
Expose/Hide/Resize/Destroy)
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GLUT Program Structure

• Initialization and window/menu setup
• Interface callbacks
• Handle mouse, keyboard input
• Display function
• Draw world (including camera management)
• Idle function
• Runs when no events pending

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GLUT Interface Callbacks

• Keyboard
• Key press, key release, window location
• Mouse
• Enter/leave window, button down/up, drag
• Menu
• Item select

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GLUT Display Callback

• Responsible for entire display process
• Clear buffers
• Set up camera, GL matrix stacks
• Draw objects (including multipass rendering)
• Swap front/back buffer
• Good place to put per-frame world updates
• physics, collision, trackers

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GLUT Idle Callback

• Invoked when events not being received from
  window system
• Typical uses
• request redraw (continuous update)
• update simulation clock
• No guarantee on when itll be called!

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What GLUT Doesnt Do

• World and model management
• Load and place and render models yourself
• Camera management
• Manage GL projection stack yourself
• Motion control
• Arcball? Drive? Strafe? Look around?
• Multipipe anything

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Outline

• Introduction
• GLUT
• GLVU
• Where to learn more
• Questions and Answers

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GLVU Overview

• Object management
• Several polygonal file formats supported
• Objects can render themselves
• Camera and simple navigation
• Walk, translate, examine, look around
• Easily extensible
• Sits on top of GLUT

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GLVU System Diagram
User Input Handlers
GLVU Model Formats
GLVU Input Handlers
User Idle Func
User Display Func
GLUT
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GLVU System Architecture

• Everything is object-oriented C
• Components all inherit from base classes
• Camera, Object
• Default GLUT keyboard and mouse handlers provided
• User typically extends rather than replaces
• GLVU divided into Core and Modules

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GLVU Writing a Program

• Just like writing a GLUT program, except
• Load models by instantiating objects
• Call Display() methods instead of rendering by
  hand
• Motion handlers already provided

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GLVU Core

• Perspective Camera
• VRML, BFF, OBJ, TRI, WFF model formats
• Bounding boxes
• PPM images (for texture maps)
• Vector, Matrix math library
• Walk, Examine, Look, Translate movement modes

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GLVU Modules

• IBR far-field representations
• Textured depth mesh, environment-mapped cubes,
  layered depth images,
• Light Cameras (place lights by moving viewpoint)
• Large Model utilities (cells, memory management)
• See Bill Baxter (baxter_at_cs) for latest list and
  owners

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Extending GLVU

• New model formats
• Just write a loader and a display method
• Image-based rendering
• Most work goes into display method
• Almost anything can be cast as an Object
• Can always override default GLVU input handlers
• Trackers, button boxes, joysticks...

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User Interface Toolkits

• Many available choose your favorite
• TCL/Tk
• http//dev.scriptics.com
• GLUI
• http//www.cs.unc.edu/rademach/glui
• FLTK
• http//www.fltk.org

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Outline

• Introduction
• GLUT
• GLVU
• Where to learn more
• Questions and Answers

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Where to Learn More

• Read the example code!
• GLUT
• http//reality.sgi.com/mjk_asd/glut3/glut3.html
• GLVU
• Bill Baxter (baxter_at_cs) can tell you how to get
  the source

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Outline

• Introduction
• GLUT
• GLVU
• Where to learn more
• Questions and Answers