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Faking blury Refractions using Reflections
Like
I mentioned in the reflection level
map section, we only want the leaf to
reflect its environment, in such a way
that it will look as the leaf is partially
see trough but we don't want our leaf
to reflect other objects in our scene
in this case, like I mentioned before,
a leaf's reflections and what you see
trough it would have a blur to them
because light would get distorted as
it passes trough and reflects from the
leaf therefore making things you see
trough it and are reflected by it look
blurry. The point is that raytrace reflections
don't have the ability to make blurry
reflections or refractions, so the way
to get around this is by using a blurry
environment/reflection maps. What you
would do is render everything that is
behind the leaf and use that render
as the leaf's environment and the render
environment. Here's a render with en
environment with some spheres set up
as the leaf's environment map with a
blur applied to it. As you can see in
this render, the spheres that you see
trough the leaf are more believable
because of that slight blur.
As
we already know, no objects reflect
at the same amount throughout its surface
in the same way no object has perfect
reflections, all reflections have a
slight blur to them, even the reflection
of a chrome metal, the only thing that
would have perfect reflections is a
"perfectly clean" mirror,
if that mirror was touched by a hand
or got slightly wet witch in hand collected
some dirt, those areas would have duller
reflections than the rest, what this
mans is that raytrace reflections would
only be accurate when applied to a perfectly
clean mirror doe to the inability to
blur reflections, therefore making reflection
mapping more essential. If your 3d package
has the ability to blur raytrace reflections
than you should defiantly put it into
practice but like faking translucency,
faking more accurate reflections is
also an essential skill that you must
master especially if you consider being
a texture artist for a production house
since often times this type of things
are faked using maps in order to save
render time.
So
under the raytrace controls rollout
uncheck "raytrace reflections"
and "raytrace refractions"
under raytrace enable, apply the same
map you would like to use as the background
as your environment map, feel free to
use any outdoor environment you might
desire, under the coordinates rollout
give this map a blur value of about
30 and change the mapping type to "screen"
because we want to make the leaf appear
to be see trough therefore the leaf's
reflection environment has to have the
same position and resolution as the
render environment background.
Click
on the go to parent button to go to
the leaf shader's base level, apply
a falloff map to the reflection channel,
change it's falloff type to "fresnel",
uncheck "override material IOR"
and apply our reflection level map to
the second slot of the falloff map (slot
with a default color of white). Click
the go to parent button again and under
the "raytrace basic parameters"
give index of refl (refl short for reflection)
a value of 4. to clear things up a bit,
fresnel is a real world effect that
causes areas that are further away from
the viewer appear to be more reflective
than areas that are closer to the viewer,
the Index of reflection parameter controls
the amount of between the reflection
amount of the faces that point directly
at the camera and the faces that point
away from the camera, the higher the
IOR the more the object would appear
to reflect and the smaller the difference
between the reflections amount of the
faces pointing toward and away from
the camera. An IOR of 4 seemed right
in this case because we want our leaf
to take some of the color from its environment
but not enough to make it look as if
the leaf was composed of thin plastic
and that finishes off this section.
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