Color and Shading
Color Models
Need
to be able to quantify and describe colors numerically in a computer
Components
can be described spatially using different color models
Software
systems often provide several models to assist color creation
RGB
color model
Based
on additive mixing
Color
from direct light combines by adding, known as additive mixing
Red
and green lights shining at same spot on white canvas (red and green add to
create yellow)
Used
in stage lighting, photography, interior design, computer monitors
Primary
red, green, blue are added to create other colors
Adding
all primaries creates white
Maya
provides color specification using RGB color model
Note
sliders are colored to indicate colors formed if added
HSV
color model
Color
defined by three components: hue, saturation, and value
Represents
a more intuitive representation of color selection
Select
a color, then adding levels of black or white to produce final color
The
primary color selected around a color wheel
Primary
colors often associated with primary emotions
Yellow
is closest to light, warmth
Red
is most emotional and active
Blue
is passive and soft
Saturation
Relative
purity of a color from the hue to a shade of gray
Adding
more white lessens purity, less saturated
Saturation
of 0.0: shade of gray, no hue
Saturation
of 1.0: pure hue
Fully
saturated color is simple, highly emotive and expressive (circus)
Less
saturated colors are subtle and restful (dentist’s office)
Value
Relative
intensity or brightness from light to dark
Tonal
gradations (tone is constant, not affected by color)
Adding
more black lessens brightness, less value
Value
of 0.0: 100% black added
Value
of 1.0: 0% black added
Maya
provides color specification using HSV color model
Note
sliders are colored to indicate colors formed if added
Shading Models
Simulates
how light interacts with surfaces to create different types of surface
appearances or quality
Shading
models calculate the color of a pixel(s) from user-specified shading
attributes
Based
on physics with several simplifying assumptions, also called illumination,
lighting, or reflection models
Different
shading models simulate different surface appearances (e.g. rough, smooth,
velvet-like, …)
Shading Panel
Hypershade - Panel for working with materials
Note:
useful layout, Panels->Saved
Layouts->Hypershade/Render/Persp
Consists
of three separate areas: Create
Bar, Visor and Work Area
Icon
buttons display and hide Create
Bar, Visor and Work Area windows
Visor
Catalog
of all appearance-related elements (materials, textures, lights, cameras,
…)
Icons
for default materials (lambert1, particleCloud1, shaderGlow1)
NOTE: Do not adjust attributes for the
default materials
With
heavy scenes, Visor becomes very useful for selection (i.e. lights)
Work
Area
Used
to build up more complex surfaces from simple material node
We
will use this area when we study surface mapping, feature, and textures
Create
Bar
Displays
various types of nodes used to build up complex surface treatment
Shows
all available types of materials, textures, lights, and low-level utility nodes
Shading Materials
In Maya, shading models are referred to as Materials
Complex
surface treatments are built from first selecting a material (shading model)
User
then modifies various material attributes to create different appearances
Materials,
as with other objects in Maya, are nodes with attributes
Creating Materials (several
methods)
RMB in Hypershade work
area (Create->Materials->…)
MMB drag and drop from Visor Create directory to Work Area
Panel Create menu
selection (Create->Materials->…)
RMB marking menu on object (Materials->…)
Applying Materials (several
methods)
MMB drag and drop material node on object in scene
Select object, shift-select node, RMB menu on node, Assign Material to Selection
RMB marking menu on object (Materials->…)
Material Types
Lambert
Simulates a flat, matte, diffuse, rough surface
Light reflects and scatters in several directions
No shiny highlight (specular reflection)
Reflection greatest where surface orientation is coincident with light direction
Phong
Simulates a shiny, glossy, smooth surface
Combines lambert material with shiny highlight
Specular highlight dependent on viewing angle
Phong E
Similar to phong, softer highlights than Phong
Renders slightly faster than Phong
Blinn
Softer highlights than Phong models
Useful for simulating metallic surfaces
Less likely to exhibit highlight artifacts as in Phong models
More flexible highlight parameters
Anisotropic
Simulates surfaces made up of small, invisible “grooves”
Specular reflection scattered unevenly following grooves
Useful for simulating hair, velvet, brushed metal, compact discs
Material
Attributes
Materials,
as with any other node, can be adjusted by modifying its attributes
There
are several ways to load material attributes in the Attribute Editor
Click
on the material node in the Hypershade and select Attribute Editor
Click
on the material node, ctrl-A will activate the Attribute Editor
RMB over object with material, Materials->Material Attributes
Material
attributes are rich in functionality to create interesting appearances
Experiment
and push the settings to explore how each attribute functions
Color
Base color of the material node
Transparency
Opacity of material, “see-through”
Value of 0.0: completely opaque (black)
Value of 1.0: completely transparent (white)
Ambient Color
Adds color to all parts of object
Adding deep purple
Incandescence
Adds value to the color and intensity of light being reflected from object
Simulating emission of light from object itself
Does not radiate light nor illuminate other objects
Adding a slight dark green incandescence
Translucence
Allows light to pass through opaque material
Simulates thin materials allowing light passage (i.e. blinds, lampshades, leaves, wax paper)
Will also allow shadows to be cast on backside of object between light and material
Example
Spot light toward camera added inside of sphere
Torus added between light and inside of box
No Translucence
Translucence adjusted to 0.6
Translucence Focus
Focuses translucent light in the direction of the light (lower values
scatter light)
Decreasing Translucence
Focus
Increasing Translucence
Focus
Diffuse
Degree to which material reflects light equally in all directions
Scaling factor of base color
Diffuse factor: 0.45
Specular Shading
Not available in Lambert model (only Blinn, Phong, PhongE, Anisotropic)
Variety of attributes in different models
Can modify size, color, falloff of highlight
Tip: size of highlight should match light position, size, type
Tip: light gray value will blend highlight with base color more naturally
Tip: highlights and transparency
May need to increase intensity to see on transparent surfaces
Increasing specular intensity (value component)
Tip: highlights and metallic surfaces
Use base color for specular color
Can copy exact colors by sampling other colors
Open
Specular Color chooser
Select
eye-dropper icon
Sample
color from base Color button
Specular
color contains same color
