Overview and applications

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13 Δεκ 2013 (πριν από 3 χρόνια και 8 μήνες)

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Overview and applications

Yasir O. Sinada

Olivier Steiger

Historical background and characteristics

OpenGL (“Graphics Library”) was introduced in 1992 by Silicon Graphics

Based on older IRIS GL

Specifications governed by the OpenGL Architecture review board

Compaq, Evans & Sutherland, Hewlett
Packard, IBM, Intel, Intergraph, Microsoft, and Silicon Graphics)

Current version: 1.2


Platform independent: can run on consumer electronics, PC’s, workstations, etc.

Backward compatibility required in new versions

Supported by many hardware accelerators => fast

Architecture and terminology

: whatever we want to render; a model is made up of primitives

: closed, flat surface bounded by at least 3 line segments. Basic building block in OpenGL

: corner of a polygon. Polygons are defined by their vertices (coordinates: x, y, z, w)

Matrix transformations
: allows to scale, rotate and translate vertices

Modelview matrix: turns the raw model coordinates into coordinates as viewed from viewpoint

Projection matrix: clips out vertices that are out of the specified viewing volume

Perspective division
: generates the
normalized device coordinates

using w. Usually, w=1

Viewport transformation
: 3D coordinates are turned into 2D framebuffer coordinates (=rasterization)

: turns the model into a shaded, textured and illuminated scene

Fig.: Processing pipeline



The ten OpenGL primitive types

All objects have to be made up out of these ten primitives!

Programming syntax: an example

Source code

Application: medical sciences

Virtual endoscopy
: internal examination of human body without surgery

=> painless teaching of endoscopy

Augmented reality
: combine real image with overlaid graphics

=> guiding of knife or needle during brain surgery

=> overlay of ultrasonic 3D scan and patient

Surgical simulation

=> data glove and head
mounted display allow

training of difficult processes without risk

Finite element simulation of heart defibrillation

=> allows to optimize the size and locations of the needed electrodes as well

as magnitude of defibrillation shocks

Real world


Application: medical sciences (II)


Avoids unnecessary interventions

No need for patients (rare diseases)

Assistance for difficult procedures


Applications need to run in real time (10
15 frames/sec), BUT:

the model for simulation of heart defibrillation is composed of more than
1.5 million tetrahedral


250000 degrees of freedom

4 billion floating
point ops
for solution

Resolution needed for diagnostics:
2000x2000 pixels

=> data sets have sizes about 13.4 GByte

Application: geology / mining

The use of 3
dimensional models allows

Intuitive visualization of big data sets (measures)

Impact simulation before construction

Application: industrial design

Visualization of not yet realized prototypes, which can be located in their future context

=> potential clients get a better opinion of the product, can give feedback

Behavior visualization: thermal graphs of airplanes, pressure distribution in mechanical structures, …

=> weak points are easily located and optimizations can be tested on virtual model

Application: special effects

Used in motion pictures, advertisement, video games and TV industry.

Today, this is the biggest application field for 3D graphics!

Distinguish between “realistic” 3D (Jurassic park) and “Virtual
3D” (A bug’s life)

Application: special effects (II)

The high resolution and frame rate (especially for movies) requires powerful equipment

=> High cost for FX

Compositing is also more used than in other fields

=> many difficulties due to synchronization, color correction, realistic texturing, …

OpenGL future

Language improvements:

often used extensions (fog coordinates, shared texture color palette, point parameters, …)

will get included into core OpenGL

sequences of small functions get grouped into more powerful extensions

Hardware evolution:

as hardware gets cheaper, many software functions will be included into hardware

=> speed improvement

standard video boards support OpenGL (motivated primarily by the game industry…)

New application:

data compression (MPEG

“Virtual reality” (3D navigation)

More information?


Ron Fosner. “OpenGL. Programming for Windows 95 and NT.”

Wesley developpers press, 1998


www.opengl.org: general OpenGL site


www.sgi.com/software/opengl: some information, a lot of advertisement


Soferman, Blythe and John. “Advanced Graphics Behind Medical Virtual Reality: Evolution of

Algorithms, Hardware and Software Interfaces.”

Proceedings of the IEEE, vol. 86, No. 3, March 1998

Class questions

Why does OperGL provide only 10 primitives?

The conception of OpenGL goes back to 1992, when machines were slow and hardware extensions

expensive. Silicon Graphics wanted to provide a graphical language which allows the creation of any

kind of objects without requiring a too big computational amount; however, the goal was not a language

for the efficient creation of graphical objects (circles, cubes, …), which can be realized with other

software, but for scenes with lights, textures and animations.

In order to do so, they brought up ten fundamental shapes, or primitives, and associated them with many

powerful lightning and matrix operations. The primitives are just the “fundamental alphabet” allowing

the creation of complicated scenery with simple objects. More primitives would result in an increased

language complexity, slowing down the computation in certain cases.