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Hello and welcome to lecture number 2 in the
course Computer Graphics.
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So, before we start, let us recap what we
have learned in the previous lecture.
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In the last lecture if you may recall, we
got introduced to the field and talked about
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the basic idea.
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That means, what is computer graphics, what
it deals with.
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Now today, what we are going to do is, we
will discuss the historical evolution of the
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field.
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And also we will discuss the issues and challenges
that are faced by researchers in this area.
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Historical evolution knowledge is always beneficial
for the broader understanding of the subject.
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So, we will go into a bit details of the evolution
followed by discussion on the issues and challenges.
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In the early days when computer just started
appearing, that means in the 1940s, 50s of
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the last century, displays constituted a terminal,
a terminal unit capable of showing only characters.
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So, in earlier days we had displays that used
to show only characters, there was no facility
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or no way to show anything other than characters.
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Subsequently, the ability to show complex
2D images was introduced, that is the later
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developments.
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Now, with the advent of technology other things
changed.
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We have now higher memory, capacity and increased
processor speeds.
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Along with those changes, the display technology
also improved significantly, so we had 3 broad
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developments, memory capacity enhancement,
processor speed increase, as well as improvement
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in display technology.
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Now, all 3 contributed together to display
or to make it possible to display complex
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3D animations which are computationally intensive
and which assumes that we are capable of performing
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the computations in real time.
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How computers computationally intensive these
processes are, we will see in the subsequent
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lecture.
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In fact, that is the core content of this
course.
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Now, if we look closer to the 3D animation,
then we will see that there are 2 aspects,
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one is synthesize of frames and the second
one is combining the frames together and render
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them in a way such that it generates a perception
of motion or generates the motion effects.
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Now, synthesis of frame as well as combining
them and rendering them on the screen to generate
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motion are complex processes and they are
also resource intensive.
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They require lots of hardware resources.
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So, these are the main focus areas of present
day computer graphics activities, how to make
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the computer these processes workable in the
modern day computing environment.
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Now, we are repeatedly talking about the term
computer graphics but it has an origin.
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So, the term was first coined by William Fetter
of the Boeing Corporation in 1960.
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That is 60 years ago.
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Subsequently, Sylvan Chasen of Lockheed Corporation
in 1981 proposed 4 phases of the evolution
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of the field.
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What are those phases?
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The phase was concepts to birth which is typically
considered to be between 1950 and 1963.
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This is also known as the gestational period.
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The second phase is the childhood phase of
short duration 64 to 70 in the last century,
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then we have adolescence, this is again somewhat
significant phase and span between 1970s to
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early phase of 1980s and then we have the
adulthood which is still continuing starting
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from the early 1980s.
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So, these are the 4 phases that was proposed
by Sylvan Chasen in 1981, gestational period,
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childhood, adolescence period and adulthood.
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Now, let us have a quick look at the major
developments that took place in each of these
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phases.
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Let us start with the first phase that is
the gestational period between 1950 and 1963
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at the early stages of computers.
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Now, if you are aware of the evolution of
computers in the early phases, then you know
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that, that phase the gestational period also
coincides with the early developmental phases
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of the computing technology itself.
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So, that was the phase when technology evolved.
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And nowadays, we take for granted the availability
of interfaces that are popularly known as
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graphical user interfaces.
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So, we get to see it on all of our computer
screens mostly, if we are using desktop, laptops
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or even smartphones.
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But in that phase, in the gestational period,
the GUI concept was not there.
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In fact, nobody was even aware of the possibility
of such an interface, it could not be imagined
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even.
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Now in that phase, there was one system developed
which was called SAGE, which stands for Semi
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automatic, Semi Automatic Ground Environment.
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Now, it is developed by or for the benefit
of the US Air Force, which is part of a bigger
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project called the Whirlwind project which
was started in 1945.
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Now, the SAGE system is an early example from
this phase of gestational period demonstrating
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the use of computer graphics.
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What this system does or what this system
did, now the basic idea of the project was
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to get the positional information of an aircraft
from rudder stations that is typically the
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job radar network.
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Now there is an operator who like this operator
here, who was sitting in front of a screen,
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as you can see, but not the traditional screens
that we are accustomed with but early version
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of a screen.
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And on this screen aircrafts are shown and
on the aircraft other data, the data received
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from the radar was superimposed.
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So, essentially what we have is that on the
screen, a geographical region is shown and
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on that region the aircraft information is
shown.
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There was more one more aspect of the system.
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So, it was actually in a sense interactive
system, so the operator can actually interact
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with the system with the use of an input device
called a light gun or pen, light pen.
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Now, if there is an aircraft shown on the
screen, the operator can point the pen to
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that aircraft to get the identification information
of the aircraft.
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So, when the gun was pointed at the plane
symbol on the screen an event was sent to
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the Whirlwind system which in turn sent the
details as text about the plane or about the
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identification information of the plane which
was then displayed on the screen of the operator.
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Something like this.
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As you can see this is a light gun or light
pen, operator is pointing the pen on the screen
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where an aircraft symbol is shown and once
the pointing is done, then the system sends
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message to the overall system, Whirlwind system
which had all the information, which is sent
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back to the interface to be seen by the operator.
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So as I said, the system SAGE which is part
of the Whirlwind system had traces of interactive
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graphics, where the interaction was done with
the light gun or the light pens, but it was
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still not fully interactive the way we understand
interaction in the modern context.
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True potential of the interactive computer
graphics came into picture after the development
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of another system called Sketchpad by Ivan
Sutherland way back in 1963.
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So, this Sketchpad system was a part of doctoral
theses of Ivan Sutherland at MIT.
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And this system actually demonstrated the
idea as well as the potential of an interactive
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graphics system.
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Like the SAGE system in Sketchpad also, the
interaction was done through light pen and
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it was mean to develop engineering drawings
directly on a CRT screen.
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So, here the operator need not be a passive
input provider instead active input can be
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given in the form of creating drawings itself
on the screen.
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An example is shown in this figure as you
can see, this is the screen and on the screen
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the operator is holding light pen to create
a drawing here.
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Now this Sketchpad system actually contains
many firsts.
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It is widely considered to be the first GUI,
although the term GUI was still not popular
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at that time, it is also credited with pioneering
several concepts of graphical computing namely
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how to represent data in memory, how to deal
with flexible lines, ability to zoom in and
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out, draw perfectly straight lines, corners,
joints.
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These are things that nowadays we take for
granted but these were very, very difficult
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at the time and sketchpad actually managed
to demonstrate that these are possible.
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Accordingly, Sutherland is widely acknowledged
by many as the grandfather of interactive
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computer graphics.
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Now along with SAGE and Sketchpad, this period,
gestational period also saw development of
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many other influential systems.
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During this phase first computer game called
Spaceware was developed in 1961 on a PDP-1
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platform which is an early computing platform.
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IBM also developed the first CAD or Computer
Aided Design system, recollect our previous
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lecture these systems are meant for helping
engineers create mechanical drawings and test
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various thing without actually requiring to
build the system.
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And in the gestational period, IBM came up
with this first CAD system in 1964 although
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the work started in 1959.
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Now, the gestational period was followed by
the childhood period, which is reasonably
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short duration period only of 6, 7 years.
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Now, in this period now much significantly
new things happen only whatever was developed
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earlier in the gestational period, further
development took place along those lines and
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consolidation took place of the earlier ideas.
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Then came the adolescent period, mostly confined
to the 1970s and early phase of 1980s.
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Now, in this phase again, many new things
happen, in 1971 Intel released the first commercial
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microprocessor called the 4004.
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Now, as we all know, with the coming of this
microprocessor, a paradigm shift took placed
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in the way computers were designed and that
in turn impacted the computer graphics field
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in a significant way by making computations
less costly and affordable.
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As a result, in this period several interesting
things happened, primarily two types of developments
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took place, one is techniques for realistic
3D graphics and several applications were
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developed during this phase particularly in
the entertainment and movie making fields.
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As a result of those applications, people
started noticing the potential of the field
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and invested more and more time and money
so, both the development were significant
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in the context of overall evolution of the
field.
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Now, what were the works that were done for
realistic and 3D image generation?
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One important development was the working
on the lighting models.
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Now, these models we will learn later.
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What these models were meant to do, were to
assign colors to pixels and this coloring
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of pixels or smallest graphical units on a
screen is very important to give us a perception
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of realistic images as we all know.
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And we shall see in details in later lectures.
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Apart from that, another thing took place
that is development of texture mapping techniques,
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now texture is basically patterns that we
get to see on the surfaces.
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So, if we can impose textures on our artificially
created object surfaces, then definitely that
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will lead us to a more realistic image representation
and that development took place in this adolescence
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period.
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So, the first work was done by Catmull in
1974.
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First notable work, as you can see, that on
this object some textures are shown, because
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of that, we are able to make out that it is
a 3D object and it is having certain characteristics.
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So, without texture, it will look dull and
non realistic.
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An advanced form of texture mapping was done
through Bump mapping by Blinn in 1978.
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Like the example shown here, on the object
surfaces, we can see that that special type
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of textures were incorporated, inserted to
make it look more real, natural.
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These are called bumps, Bump mapping.
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Also another development took place which
is an advanced technique of creating 3D images
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that is called Ray Tracing and first notable
development took place in 1980s in the adolescence
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period, using this technique, we can develop
realistic 3D images on a 2D screen, in a more
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better way than using the other techniques.
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Now, these are techniques that were developed
to improve the quality of the synthesized
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images, to make them more realistic, more
natural.
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So, to recap, broadly 4 approaches were develop
in this phase.
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First one is lighting modern, basic work on
the lighting model followed by texture model
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and bump modeling, bump mappings and finally
Ray tracing methods.
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Apart from that, as I mentioned earlier, another
strand of development that took place during
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this phase was development of several applications
of computer graphics, whatever was the state
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of the art at that time based on that several
applications were developed.
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Particularly in entertainment and movie making.
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So, in 1973 the first movie came out named
Westworld, which was the first movie to use
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computer graphics.
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This was followed in 1977 by the movie Star
Wars, I think most of you, if not all, may
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be aware of this movie.
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So, the first movie came out in 1977 and it
became hugely popular throughout the world
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and as a result, people learned about the
potential of computer graphics in a more compelling
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way.
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The adolescence period was followed by the
adulthood period, starting from the early
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phase of 1980s.
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Now, in this period, the field entered the
adulthood with the release of IBM PC in 1981.
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Now as we all know, after the advent of the
PC or personal computers, computers became
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a mass product, earlier it used to be confined
to only a few people who were well educated
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in an advanced stage of studies and primarily
does research or development works using this
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but after the advent of PC proliferated and
become a mass product.
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And since it had become a mass product, focus
now shifted to the development of applications
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that were appealing to the masses.
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And using computer graphics lots of such applications
were developed and focus shifted from graphics
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for expert to graphics for laymen.
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And as a result, we got to see several developments
including the development of GUIs and the
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associated concepts.
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In fact, so many developments took place that
it gave rise to a new field of study, which
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is called human-computer interaction or HCI
in short.
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One thing happened during this phase, a self
sustaining cycle of development emerged, what
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is that?
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As more and more user friendly systems emerge,
they create more and more interest among people,
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in turn that brings in new enthusiasm and
investments on innovative systems.
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So, it is a self sustaining cycle of development,
more and more applications are there that
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is appealing to more and more people and the
people in turn want more and more so, more
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and more investment came and it continued
and it is still continuing.
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And as a result of this self sustaining cycle
of development, other associated developments
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took place.
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So, from CPU, we migrated to GPU or graphics
processing, dedicated hardware for graphics,
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storage capacity improved significantly to
be able to store and process large amount
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of data required for 3D realistic graphics.
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So, now we are talking in terms of terabytes,
petabytes, instead of kilobytes or megabytes
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that used to be the case earlier.
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Similarly, display technology have seen huge
improvement from the earliest cathode ray
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tubes to modern day touchscreens or situated
walls or even better things.
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So, all this took place because of this self
sustaining cycle of development.
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So, we can say that these technological developments
brought in a paradigm shift in the field and
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we are now in a position with the help of
new technology to develop algorithms to generate
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photorealistic 3D graphics in real time.
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So, all these things are important and this
will form the core subject matter of our discussion
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in subsequent lectures.
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Now, note that all these are computation intensive
process and because of the advancement in
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technologies, such computation intensive process
has become manageable, possible to implement
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in real time.
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And since we are able to do those things now
then the appeal and application of computer
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graphics have increased manifold and they
presence of all these factors implies that
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the field is growing and will continue to
grow in the foreseeable future.
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So, that is in brief the evolution of the
field, 4 phases starting with the gestational
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period to the adulthood and the major developments
we briefly discussed.
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Now, let us shift our focus to another important
aspect of the field that is what are the issues
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and challenges that confront workers in this
field?
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Now, in the formative stages of the field,
primary concern was as we all know, generation
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of 2D images or 2D scenes.
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But again as we have already discussed that
subsequently changed and 2D graphics is no
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longer the thrust area and we are mostly focused
on, nowadays we are mostly focused on the
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generation of 3D graphics and animation.
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In the context of 3D graphics and animation,
there are 3 primary concerns related to software,
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software development for the system.
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One is modeling which essentially means creating
and representing object geometry in 3d world
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and here we have to keep in mind that we are
not only talking about solid geometric objects,
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but also some phenomena such as bellowing
of smoke, rain, fire, some natural events
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phenomena so, how to model both objects as
well as phenomena, that is one concern.
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Second concern is rendering, essentially creating
and displaying 2D image of the 3D objects,
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why 2D image?
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Because our screen is 2D so we have to convert
the 3D objects into a 2D form.
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So, then this rendering deals with issues
related to displaying the modeled objects
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on the screen and there are some other related
issues involved namely color, coloring of
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the pixels on the screen, color and illumination
which involves simulating the optical process.
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Then, visible surface determinism with respect
to the viewer position, textured patterns
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on the surfaces or texture synthesis to mimic
realism, 3D to 2D transformation and so on.
00:31:05
So, these are the issues that are there in
rendering.
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Then the third issue, third major issue related
to graphic software is animation, describing
00:31:21
how the image changes over time so, what it
deals with?
00:31:28
It deals with imparting motion on the objects
to simulate movement, so, give us a perception
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of movement.
00:31:41
Then the key concerns here are modeling of
motion and interaction between objects during
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motion.
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So, the 3 major issues related to software
are modeling of objects, rendering of objects
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and creating of animation.
00:32:00
Now, there are some hardware related issues
as well.
00:32:05
Why those are important, because quality and
cost of the display technology is of important
00:32:15
concern, because there is always a tradeoff
between the two, quality of the hardware as
00:32:23
well as the cost, so we cannot get high quality
in low cost and vice versa.
00:32:33
And while building a graphics system application,
we need to keep in mind this tradeoff.
00:32:40
Along with that, we need to keep in mind selection
of appropriate interaction device because
00:32:49
nowadays we are talking of interactive computer
graphics.
00:32:53
So, the interaction component is important
and it is important to choose an appropriate
00:32:58
mode of interaction or input device such that
the interaction appears intuitive to the user.
00:33:08
The user should not be forced to learn complex
patterns or complex operations, it should
00:33:16
be as natural as possible.
00:33:19
Finally, design of specialized graphic devices
to speed up the rendering process is also
00:33:26
of utmost importance.
00:33:30
Because graphics algorithms are computation
intensive and if we can have dedicated hardware
00:33:42
to perform those computations, then we can
expect better performance.
00:33:47
Now, the issue is how to design such hardware
at an affordable cost and that is of primary
00:33:56
concern related to hardware platforms for
computer graphics.
00:34:04
So, from the point of view hardware, we have
this quality of the hardware as well as cost
00:34:14
tradeoff to keep in mind also, we have to
keep in mind the type of input device we are
00:34:20
using as well as the dedicated graphic systems
that we can afford.
00:34:26
Now, one thing we should note here is that
in this course, we shall learn how the issues
00:34:33
are addressed, but we will not discuss issues
related to animation, we will restrict our
00:34:38
discussion to modeling and rendering of 2D
images on the screen.
00:34:49
So, whatever we have discussed so far can
be found in chapter 1 of the book that we
00:34:59
are following.
00:35:01
You are advised to go through section 1.1
and section 1.2 for getting more details on
00:35:07
the topics that we have covered today.
00:35:10
So, that is all for today, we will meet again
in the next lecture, thank you and good bye.
