SE 313 – Computer Graphics
Lecture 12: Lighting and Materials
Lecturer: Gazihan Alankuş
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Projects
•
•
•
•
Weekly reports
Video
Sources
Final demo
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Projects
• Weekly reports
– Help me understand your own contribution
• Video
• Sources
• Final demo
3
Projects
• Weekly reports
• Video
– Prepare a video that demonstrates your project
– Example: https://www.youtube.com/watch?v=auurLcPFGrs&list=PL0E431E2DD85623D5&index=6
– Should include:
• A title scene with your names, IEU, SE 313, my name
• Project description and demonstration
• Between 2-5 minutes
– Upload to YouTube with this text(text in [brackets] are optional):
• Term project for SE 313 Computer Graphics in İzmir University of
economics. [your names (optional)]
İzmir Ekonomi Üniversitesi SE 313 Bilgisayar Grafiği dönem projesi.
[your names (optional)]
• Sources
• Final demo
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Projects
• Weekly reports
• Video
• Sources
– Give me all your source files
– Include a README file on how to use them
• Step-by-step instructions
• Versions of software that you used
• External factors
– If you had external help (downloaded models and textures, help you
received from someone else, etc.), clearly write them.
– Was this a project that was a joint project with some other class? If so,
write it down.
– If you don’t do these, you claim that it was all your work and was for this
class only. If I prove that it wasn’t, you have cheated and will be punished
according to university rules.
• Final demo
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Projects
•
•
•
•
Weekly reports
Video
Sources
Final demo
– Set up a half-hour meeting with me
– The last day for the meeting is 18th of January
• My available times may be filled before that. Be quick
and try to find a time.
– Send everything (video, sources, etc.) me 24 hours
before that
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Lighting and Materials
• Lighting
– Real-time (local illumination)
– Better (global illumination)
• Materials and surface detail
– Normals
– Materials
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Lighting and Materials
• Lighting
– Real-time (local illumination)
– Better (global illumination)
• Materials and surface detail
– Normals
– Materials
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Lighting
• Projecting 3D geometry into 2D is not enough.
Projecting
the edges
only
Projecting
the faces
Copying the object’s colors in the
2D projection does not look good
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Lighting
• We see objects through light bouncing from them
• We see different tones according to the way light
bounces
• Computers need to simulate this to create
realistic pictures
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Lighting
• Simulating light is very difficult. There can be
infinite number of rays coming from a light
source. We need something fast!
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Lighting
• Observation: if the light can bounce directly
from the light source to the eye, the surface
looks lighter
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Lighting
• Observation: if the light cannot bounce
directly, then the face looks darker
• We use these observations to simulate lighting
• We use the normal vector to determine the
orientation of the face
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Two types of lighting
• Diffuse reflection
– We see darker color
even if light does not
bounce directly to the
eye
• Specular reflection
– We only see color when
light bounces directly to
the eye
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Ambient lighting
• There is so much light that comes from the
sun, light bounces from everything in the
environment
• Even if you are in a closed room in daytime,
there is light in the environment
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The three types of lighting
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Emission
• Emission is the fourth
type of lighting
• Simulates objects that
emit light by
themselves (if it’s a
lamp, for example)
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Different colors for different lighting
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Simulating lighting in real time
• These four types of light calculations
(ambient, diffuse, specular, emission) help us
simulate lighting in computers in real-time.
• This way we can have video games that look
real and react instantly
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Lighting and Materials
• Lighting
– Real-time (local illumination)
– Better (global illumination)
• Materials and surface detail
– Normals
– Materials
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Global Illumination
• Simulating light locally is an approximation.
Light bouncing from nearby objects is ignored.
• There are algorithms to simulate light better.
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Radiosity
• Relationships between
faces of polygons are
computed to see
whether they would
illuminate or shade
each other
• Slower than local
illumination, better
results
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Ray tracing
• Light is reversible
• Rather than simulating
the actual lights, trace
light rays that would
come to the eye
• Start from the eye and
see whether you reach a
light source after
bouncing on objects
• Slower than radiosity.
Very real-looking results.
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How they are used in practice
Local Illumination
• Real-time applications
• Video Games
• The image does not have to
be very realistic
• Renders very quickly
• What you see in Blender 3D
view
Global Illumination
• Batch applications
• Movies
• The image has to look very
real
• Renders slowly
– Render farms with many
supercomputers are used for
long movies
• What you see in Blender
Render view
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Lighting and Materials
• Lighting
– Real-time (local illumination)
– Better (global illumination)
• Materials and surface detail
– Normals
– Materials
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Normals
• Surface normals
determine the color
tones that the surface
will have because of
lights
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Normal Mapping
• Surface normals
determine the color tones
that the surface will have
because of lights
• Surfaces with such detail
requires too much
geometric detail and
renders slowly.
• We fake it by using
normals from a detailed
model on a non-detailed
model
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Normal Mapping
• With normal mapping, you can have a mesh
with less detail that looks like another mesh
with more detail
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Lighting and Materials
• Lighting
– Real-time (local illumination)
– Better (global illumination)
• Materials and surface detail
– Normals
– Materials
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Materials
• Things that determine the color of a surface
– Properties of lights
– Properties of surfaces
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Materials
• Things that determine the color of a surface
– Properties of lights
• Position
• Colors and intensities for ambient, diffuse, specular
components
– Properties of surfaces
• Normals
• Colors for how ambient, diffuse and specular
components will be reflected
• Emission
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Materials
• Matching properties of the light and the
surface are multiplied together
Diffuse color
of the light
Diffuse color of
the material
Visible diffuse
color on the
surface
LR
LG
LB
MR
MG
MB
SR
SG
SB
Red light
White material
Red surface
(1, 0, 0)
(1, 1, 1)
(1, 0, 0)
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Next week
• We will practice these in Blender next week
• Now we will have a lab that you will be graded
in
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Lab
• Modeling
• Texturing
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Lab: Modeling
• Starting from a cube,
model this table.
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Lab: Modeling
• Model the legs by
subdividing the bottom
face, extrude
individually, scale,
translate, extrude
• Model the book on the
table by creating the
rectangle by cutting the
edges one by one using
the knife tool. Then,
extrude it up.
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Lab: Modeling
• Model the drawer using
extrude.
• After taking the drawer
out, extrude inwards to
create the inside of the
drawer.
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Lab: Texturing
• Open the redwood
texture in the main uv
mapping so that the
whole model has the
redwood texture.
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Lab: Texturing
• Map the book cover on
the book cover on top
of the table.
• Create a separate UV
map for the book and
name it “book”
• Map the book image in
that UVMap
• Using the clone brush,
copy that to the main
texture
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Lab: Texturing
• Create a separate UV
map for the inside of
the drawer and name it
“drawer”.
• Map the junk in it
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Lab: Texturing
• Use the clone brush to
paint into the main UV
map from the drawer
UV map
• Leave some empty
places to give a dirty
look.
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Lab: Bonus
• Bonus1: Use other
wood textures to give a
more detailed view to
the table
• Bonus2: create other
geometry on top of the
table and texture them
with images you find on
the internet
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