Shading
Adding Color
Lambert’s law
Light a point in any direction varies as the cosine of the angle
between a vector from the point to the light source and the
normal vector of the surface at the point
n
L
q
Warnock (Flat) Shading
• Flat shading
• Decrease intensity
with distance from
light and object
• Highlights
Gouraud Shading
• Compute
shading at
each vertex
• Interpolate
shading
Problem with Gouraud Shading
• Highlights across polygons
Phong Shading
Phong Shading
Diffuse Shading
Idiffuse = kd Ilight cos q
n
L
q
eye
Specular Shading
Add specular by looking at
reflection, r
Shiny surfaces, such as a
mirror
n
L
q
q s
r
e
Phong Shading
lights
Itotal = ka Iambient +
Si = 1 I (k (N . L) + k (V . R)n )
n
L
q
q s
i
r
e
d
s
shiney
Phong Shading
n
L
q
q s
r
e
Review: Surface Properties
Perfectly Specular:
“Mirror”
“infinite gloss”
Surface
Normal
Reflected
Light
q
Phong
Specular
Model:

L R cos (q)
Andrew Glassner et al.. SIGGRAPH`94 Course 18:
“Fundamentals and Overview of Computer Graphics”
Incident
Light
Ray
Review: Surface Properties
Slightly scattered Specular:
“high gloss”
Reflected
Light
Surface
Normal
Phong
Specular
Model:
15
L R cos (q)
Andrew Glassner et al.. SIGGRAPH`94 Course 18:
“Fundamentals and Overview of Computer Graphics”
Incident
Light
Ray
Review: Surface Properties
More Scattered Specular:
“medium gloss”
Surface
Normal
Phong
Specular
Model:
5
L R cos (q)
Andrew Glassner et al.. SIGGRAPH`94 Course 18:
“Fundamentals and Overview of Computer Graphics”
Incident
Light
Ray
Review: Surface Properties
Perfectly Diffuse
“flat”, “chalky”,…
Surface
Normal
Andrew Glassner et al.. SIGGRAPH`94 Course 18:
“Fundamentals and Overview of Computer Graphics”
Incident
Light
Ray
Review: Surface Properties
Most Materials:
Combination of
Diffuse and Specular
Surface
Normal
Andrew Glassner et al.. SIGGRAPH`94 Course 18:
“Fundamentals and Overview of Computer Graphics”
Incident
Light
Ray
Rendering Realism
Cornel Measurement Lab
Rendering Realism
Real
Synthetic
Shirley, et. al., cornell
Is this real?
m fajaro, usc
Terrain Modeling: Snow and Trees Added
s premoze, et.al., utah
Rendering Realism
Morning
Evening
a preetham, e
Humans
Final Fantasy (Sony)
Jensen et al.
Artistic Shading
Is Photorealism Everything?
Is Photorealism Everything?
Enough Information…?
Just a bit more…
Or did we mean this…?
Diffuse shaded model
I = cr(ca + cl max(0, L.n)) with cr=cl=1 and ca = 0.
Just Highlights and Edge Lines
Hand-tuned Phong shading
From Jose Parramon, 1993
Shading used by Artists
Complementary Shading
Final Image
From “The Book of Color” by Jose Parramon, 1993
Tints, Tones, and Shades
White
tint
Hue
tone
Gray
shade
From Birren (1976)
Black
Creating Tones
Green to Gray (tone)
Model Shaded using Tones
Using Color Temperature
Warm to Cool Hue Shift
Constant Luminance Tone Rendering
Creating Undertones
Warm to Cool Hue Shift
Green with Warm to Cool Hue Shift
Model tone shaded with
cool to warm undertones
Combining Tones with Undertones
Green with Tone and Undertone
Model shaded with tones and
undertones
Phong Shaded Spheres
Spheres with New Shading
New Shading
Warm to Cool Shading
Phong Shaded
New Shading
Without Edge Lines
New Shading
With Edge Lines
Toon Shading
Intel: http://www.intel.com/labs/media/3dsoftware/nonphoto.htm
Toon Shading
Nvidia: developer.nvidia.com/object/Toon_Shading.html
Toon Shading
Blender: w3imagis.imag.fr/Membres/Jean-Dominique.Gascuel/DEAIVR/ Cours2002/17%20janvier/Blender-tutorial80.pdf
Non-Photorealistic Rendering
b gooch, et.al., utah
NonPhotorealistic Rendering
Shading in Maya
Hypershade
• Shading models = Materials
Material Types
• Lambert
– Flat, matte,
diffuse, rough
surface
– Reflection
greatest where
surface
orientation is
coincident with
light direction
Material Types
Material Types
• Phong
– Shiny, glossy, smooth surface
– Lambert + highlight
Material Types
• PhongE
– Similar to Phong, but with softer highlight
– Renders slightly faster than Phong
Material Types
• Blin
– Simulating metallic surfaces
– More control over highlight
Material Types
• Anisotropic
– Simulates small, invisible grooves
Material Attributes
• Color
Material Attributes
• Transparency
Material Attributes
• Ambient color
– adds color to all parts of the object
Add deep purple
Material Attribute
• Incadenscence
– Simulate light being reflect from object itself
• Does not actually affect other objects
Adding slight dark green incandescence:
Material Attribute
• Translucence
– Light pass thru opaque material
0.0
0.6
Ray Tracing
• http://www.cs.berkeley.edu/~efros/java/tracer/tracer.ht
ml
• http://www.siggraph.org/education/materials/HyperGr
aph/raytrace/rt_java/raytrace.html
Shadows
• Shadows are created with….
1) Shadow casting light(s)
– Depth Map Shadows or Ray Trace Shadows on/off (attribute)
2) Surface(s) that cast shadows
– Render Stats attribute -> Casts Shadows (checked/unchecked)
3) Surface(s) that receive shadows
– Render Stats attribute -> Receive Shadows (checked/unchecked)
Shadow Properties
• Color
• Softness: Gradiation/blurring of shadow edges
• Graininess: smoothness of shadow edge
Depth Map shadows
• Per light, shadows section,
attribute editor > Use Depth Map
Depth map Properties: Graininess
• Shadows attribute > Dmap resolution (on
light)
• Higher resolution increases rendering time
• Dmap resolution 256 512
Depth map properties: Softness
• Shadows attribute – Dmap Filter Size (on
light)
• Tip: drop Dmap resolution size, increase
filter size
• Higher filter size increases rendering time
• Dmap res = 128, filter size = 3, 5, 7
Trouble Shooting Dmap
• http://woodall.ncsa.uiuc.edu/dbock/Class/cs
c187/Lecture/LightingAndShadows.html
Ray-traced shadows
• Per light, shadows section, attribute editor –
Use Ray Trace Shadows
• Window->Render Globals, Raytracing
quality, turn on raytracing
Ray-traced shadow properties
• Softness/Graininess – smoothness of shadow
edges
• Shadows attribute – Light radius (point, spot) or
light angle (directional)
• Shadows attribute – Shadow Rays (on light)
• Tip – time consuming for soft edges w/ ray-tracing
• Light radius = 0.5, Shadow Rays = 10 (similar to
area light)
Compare
• Depth map shadows create soft edges by blurring
• Ray-traced shadows simulate a more natural
softening with distance
Point light, depth-mapped shadow
Point light, ray-traced shadow
Area lights & Ray Traced
shadows
• Increase number of shadow rays (1, 5, 20)
Depth Map Shadows