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VRay for Rhino Manual
Material: Reflection LayerThis section is
about how to add and edit the refection layer. Please click on the red cup in
the scene. Click on Edit button under Material selections in properties.
Adding
Reflection Layer
1. Click on the "+" next to Cup_red under
Scene Materials to pull out all the layers. Right click on Reflection Layer.
Select "Add new layer" to add a new reflection layer for this material. There
will show Reflection under the material control section, as it shows on the
second image below.
2. To remove a new added layer, right
click on the layer you wish to remove then select remove.
3. By Default the reflection layer has a
fresnel map which varies the amount of reflection based on the viewing angle. If
that map is removed then the reflection is constant over the whole material.
Since the reflection color is set to white this leads to complete reflection on
the whole material. This is a good setting for chrome or a mirror, but not most
materials.
4. Now we will go through the specifics
of the fresnel map. Click on Reflection on the right section, and then click on
the m box to set reflection.
5. If it is not already enabled scroll
down the box next to Type, and then select Fresnel. Fresnel IOR is to control
the reflection intensity. Keep the default value of 1.55, then click Apply.
6. Click on the Material Preview again.
The Material now has reflection quality with the same color on it.
7. Notice the "m" on the right side of
the Reflection is now changed to "M". That means the Map has some other
characteristics associated with it now. Please use the same method and apply Fresnel
to other colors and render it. The white spot on the cup is the Rectangular
light from above.
8. Below image rendered with Fresnel IOR
set to 2.5, it has more reflection and looks more like a metal texture now. The
cup has some black reflection due to the default setting of the background color
is black. Under V-Ray Option, change the color under Environment>Background to
white and see what will you get.
Fresnel
Reflections
Fresnel Reflections are a naturally occurring phenomenon that states that an
object becomes more reflective the greater the angle at which it is seen. An
example of this principle would be a window that is seen from straight ahead as
opposed to at an angle. Through manipulating the Index of Refraction (IOR) the
reflective characteristics of an object can be changed. A lower IOR means that a
larger angle is needed between the observer and the surface before the object
begins to reflect. A higher IOR means that a smaller angle is needed, which in
turn causes the object to reflect sooner. To have your renderings be more
physically correct it is recommended to have the IOR of an object correspond to
its actual IOR.
Below are six rendered samples each with a different Fresnel IOR. The last
one is a rendered with full reflection to create a chrome material.
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