Visual Details Into Shaders And Patterns
A Surface Shader
is a set of equations used to determine the appearance of a surface and
how it responds to light. A Shader is combined with Maps (Patterns) to
form a Material. Sometimes your material is refereed to as a "shader",
but for clarity sake, I will only refer to the Illumination portion of
your material as a shader.
Now lets look at your Visual Detail List, what on the list is part of
Example, Hydrant (3 shaders):
- Paint Shader
- Metal Shader
- Rust Shader
Look at your
Visual Detail List, what on the list are patterns?
Example, Hydrant (8 patterns):
requires several colors, has a paintbrush bump pattern, a pattern to
change how reflective the surface is, and the paint is worn off to
the metal in a specific pattern (4 patterns).
has some slight blemishes in color (1 pattern)
has a specific color, specific bump, and then is placed on the surface
of the hydrant in a specific pattern (3 patterns).
in the CG World:
- Lambert (Simple
- Phong (Highlight)
- Blinn (Highlight,
less distortion at glancing angles)
- Oren Nayar
(Diffuse for Rough Surfaces)
- Ward Anisotropic
Now lets choose the most appropriate shaders...
could be a Lambert with a Blinn shader for shininess
could use a Cook-Torrance shader, or a Lambert/Blinn made to look
could use a lambert, or Oren Nayar since it's very rough, and doesn't
need a specular Highlight
Here's a few lessons on shaders...
Now we look at our list of patterns. To make a successful material, you
generally want at least 3 patterns per material...
- Bump / Displacement (Disp)
- Specular Amount (Spec)
Although some specialty shaders require more patterns like a
Translucency amount, subsurface color, etc.
Patterns tend to be chains of nodes (maps) that are layered together
and then plugged into a particular channel of a material. Like in this
example, a Placement node places a Pattern, that Pattern is Color
Corrected (CC), then these Color Corrected Patterns are layered
together using a Layer node, the result of that is Color Corrected, and
then plugged into your material as a color, a bump, a specular amount
etc. At its most basic level, pretty much all Pattern Map Chains you do
for any material take on a form like this...
6) Splitting Patterns Into General And Specific Patterns
Patterns: General Patterns
are non-specific, stuff that pretty much covers your entire object. In
the Fire Hydrant example, a General Pattern
would be the brush strokes in the paint. They don't need to be anywhere
specific to read as paint.
Patterns: Specific patterns
are patterns that appear in only very specific spots. In the Fire
Hydrant example, a Specific Pattern would be the spots
that show rust, since that appears only in very specific places on the
hydrant (such as where two objects
Think of this with a traditional painters metaphor. Many painters start
in the basic colors over the entire canvas, then they add details
on top. So your basic color would be the General Patterns, and your
details would be the Specific Patterns.
Also, some companies have a specific "Shader" job and a specific
"Painter" job, usually the Shader handles the
Materials and General Patterns, Painters handles
Specific Patterns. Or in some companies you have Shader Writers and
Painters, in which case the Shader Writer
codes the shader, and almost everything else is handled by the Painter.
Some companies, one person does both the
shader, specific and general patterns.
In our Fire Hydrant Example, these are the General Patterns:
- Paint Color
- Paint Bump
- Paint Specularity
- Metal Color
- Rust Color
- Rust Bump
In our Fire Hydrant Example, these are the Specific Patterns:
- Worn Off Paint Placement
- Rust Placement
Go To Part 4...
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