6.837
Introduction
to
Computer
Graphics
Assignment
3:
Ray
Tracing
and
Phong
Materials
Due
Wednesday
October
1,
2003
at
11:59pm
This
week,
we
add
local
and
global
illumination
to
our
Ray
Caster.
Because
we
cast
secondary
rays
to
account
for
shadows,
reflection
and
refraction,
we
now
call
it
a
Ray
Tracer.
We
clean
up
and
improve
shading
calculation
(local
illumination).
We
define
an
abstract
material
class
and
derive
a
Phong
Material
class
that
implements
a
diffuse
and
a
specular
component
(highlight).
You
will
encapsulate
the
high-level
computation
in
a
RayTracer
class
that
will
be
responsible
for
sending
rays
and
recursively
computing
colors
along
them.
To
compute
cast
shadows,
you
will
send
rays
from
the
visible
point
to
the
light
source.
If
an
intersection
is
reported,
the
visible
point
is
in
shadow
and
the
contribution
from
that
light
source
is
ignored.
Note
that
shadow
rays
must
be
sent
to
all
light
sources.
You
will
add
reflection
and
refraction
effects.
For
this,
you
need
to
send
sec-
ondary
rays
in
the
mirror
and
transmitted
directions,
as
explained
in
class.
The
computation
is
recursive
to
account
for
multiple
reflections
and
or
refractions.
1
Tasks
•
Implement
an
abstract
Material
class
and
derive
a
PhongMaterial
class
that
computes
Phong
shading.
•
Update
your
intersection
routines
to
return
the
Material
of
the
intersected
object,
instead
of
just
a
simple
color.
•
Create
a
new
class
RayTracer
that
computes
radiance
(color)
along
a
ray.
Update
your
main
function
to
use
this
class
for
the
rays
through
each
pixel.
•
Treat
the
case
of
multiple
light
sources
by
accumulating
shading
contri-
butions
for
all
light
sources.
•
Compute
cast
shadows
by
sending
rays
toward
the
light
sources.
1
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•
Compute
perfect
mirror
reflection
by
sending
rays
recursively
in
the
mirror
direction.
•
Compute
transparency
effects
by
sending
rays
recursively
in
the
refracted
direction.
•
Provide
a
README.txt
file
that
discusses
any
problems
you
encountered,
how
long
it
took
to
complete
the
assignment,
any
extra
credit
work
that
you
did
and
how
we
can
test
the
new
features.
•
Extra
credit:
semi-transparent
shadows
where
the
attenuation
depends
on
the
distance
traveled
in
the
transparent
object;
nested
refracting
materials;
shadow
ray
acceleration
using
early
termination
and
without
returning
the
normal
and
material;
Fresnel
reflection
term;
other
BRDF
models
such
as
Cook-Torrance
or
Ward;
anisotropic
BRDFs;
solid
textures.

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- Fall '03
- Durand
- Light, Computer Graphics, Total internal reflection, Geometrical optics
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