Creating
a Stainless Steel Material
by Montree T. (easyyong@hotmail.com) - Smoke3dStudio

This
tutorial was written from my experience
working on metal materials personal obsevations and from photographs.
There
are 3 important things to remember when you create a stainless
steel material.
1. Strong Highlight
Although
the metal shader is the easiest way to create
a stainless steel material, it has limitation
in creating the highlight, so I prefer to use either multilayer
or anisotropic, as we can play with its several highlight shapes.
2 layers of specular level on multi layer shader

The
different between the highlight shape of the blinn shader
and the
anisotropic shader
Besides
the really strong highlight on the stainless steel, that we
can create by changing the basic specular level and glossiness
parameter, I found that there is another strong illumination
of light caused by the reflection on the stainless steel surface
(the highlight appear inside the reflection) that also looks
like another highlight. As this illumination doesn't have an
exact shape, depending on the light in the environment of the
reflection. i.e. Some appear like thin vertical lines and
we need to use anisotropy to create such effect.
Faking the highlight in the environment reflection
using anisotropic
Use
First specular layer that we have in multilayer shader
as a real highlight, so we can adjust only the specular level
to be higher and lower and use glossiness to make the highlight
look more obvious.

The First specular Level is the real specular and the Second
specular Level is the one that appear inside the reflection.
I
also make the Second specular level to be as strong as the First
specular layer,
but this time I adjust the anisotropy parameter to be higher
so the highlight shape is thinner. The orientation
will be changed as well if the effect of the anisotropy doesn't
appear correct. ( The orientation is a value in degrees
that can range from -9,999 to 9,999. Default=0.)

The
different shapes of specular highlights caused by changing
the orientations.
Put
a scratch or brushed metal map in the specualar
map slot for more detail in the material highlights.

2. Low Diffuse level
The
nature of a metal is that it has strong specular highlight and
reflection but it has a diffuse level scale (in 3ds max) lower
than a normal
shader (the brightness of the difuse color is less than
normal). If we are creating the stainleess steel with an anisotropic
shader, we have to make the anisotropy parameter lower than
default. I normally use is around 25 - 70.

3. Motion Blur Reflection
The
reflection on stainless steel is very refractive
and blurry (for example it looks like a motion
blur effect in photoshop). The best reflection
map in 3dsmax is to raytrace, but I found no
such effect in raytrace that is similar to the effect seen
on stainless steel. Though we can use "multi resolution adaptive
antialiaser blur", and the effect is similar
to using a motion blur, it is not quite
the same and it takes
a long time to render.
Put
a motion blur filter on the original environment map. (Note:
This effect does not work well on flat surfaces.)
An alternate method
is to skip almost
all the detail
in environment
map and only
recreate the strong illumination
of the reflection
highlight by
creating a new
reflection map
with a linear
gradient ramp.
As the
most obvious
reflections on
a stainless steel surface
are the lines,
this gradient ramp map should use the "explicit
map channel".

Spherical environment
gradient ramp
Tthe
reflection still
does not look
realistic as it
appears
in every part
of the surface
equally, so we
use a falloff
map to specify
the fading of
the reflection
area.

Apply
a falloff map
over
a reflection
map.

This
picture
shows the
reflection
falloff
when
using
falloff
in
the
raytrace
material.

The
reflection
is
masked
by
falloff
map.
The
fading
distance
is
specifed
by
the
falloff
type.
In
the
picture
I
used "perpendicular
and
parallel"
No
reflection map
produces
realistic effect
on
a flat
surface besides
Raytrace.
I sometimes
use gradient
ramp
maps on
anisotropy to
fake
the effect
on flat
surface. As
the
anisotropy appears
in
the specular
highlight only,
the gradient
ramp
will appear
on the
specular area
only
and fading
into the
diffuse and
ambient area.

Anisotropic
map
The
anisotropy
that
appears
on
the
specular
highlight
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