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VRay for Rhino Manual
Refraction LayerOpen file:
Cups-Refraction Original.3dm. We are going to
introduce how to add and edit the refraction layer. Select the red cup from
above. Under Properties>Material, select Edit to edit the cup's material.
Add Refraction Layer
1. Click on the "+" to the right of the Cup_Red, and then right click on
Refraction Layers. Select Add new layer. You will see the Refraction layer added
to the right of the window.
Controlling the amount of transparency
2. If you don't see the transparency from the material preview window, that's
because the Transparency is set to black. Use this color to adjust the degree of
Transparency. Click on the color and change it to white, which will give you
100% of transparency to the material.
3. Click on the Update Preview again and you will see the transparency, but
without its original red color. When you set the transparency to 100% white, no
matter what you have for diffuse color, it will not show up. It will render like
the second image below.
The color of refractive materials
When you want to apply color to a refractive material, the best way to do
this is through the Fog Color, which is located to the lower right of the
Refraction dialog box.
4. Click on Fog Color and change it to the same color as the original Diffuse
Color. Click on the Update Preview and you will see the red color show up on the
material this time.
The first image below is what you will get. Do the same changes to the other two
colors and you will get the second image below. Under Render
Options>Environment, change the background color from black to white and see
what you will get this time.
Fog Settings Explained
The appearance of Fog depends on three parameters; Fog color, Fog Multiplier,
and object size. The Fog color is a very important factor, and the wrong color
can make it hard to achieve your desired effect. It is best to set your color to
a very light or desaturated version of the desired color. The Fog multiplier
will be determined by the Fog color and the object size. The object’s size is
important because Fog is created by calculating how much light penetrates an
object. Therefore, a larger object will absorb more light than a smaller object.
This means that a single setting will not necessarily produce the same effect
from object to object. The image below is two spheres with the same
material applied to them, but the sphere on the right is 4 times larger. The
additional
images below are tests of different multipliers with a saturated and desaturated
color.
Fresnel IOR: 1.55
Refract IOR: 1.55
IOR: 1.55
Fog Color: R244, G250, B230
Fresnel IOR: 1.55
Refract IOR: 1.55
IOR: 1.55
Fog Color: R175, G250, B0
Adjusting Refractions with Index of
Refraction
IOR (Index of Refraction) is used to calculate among of the light refracted
from transparent object. The newly added IOR default is set to 1.55. Please see
the chart for typical objects' IOR value.
Default set the Refraction IOR to 1.55; please refer to images below for
setting of IOR to create desire material.
Please note that reflection and refraction IOR values are separate, but to
achieve an accurate effect these values should be the same.
The Glossiness of Refractive materials
Both refractive objects and reflective object have option setting for
Glossiness. The difference is that Reflection Glossiness only affects the
surface, where Refraction Glossiness will have an effect on the object’s
transparency.
The Glossiness of a refractive object usually used to represent different
type of glass, for example, frosted glass. The refractions will become more
blurry as the value is decreased, and at a certain point these refractions will
become so blurry that they prevent what is behind the object from being
distinguished.
Refraction Glossiness default is set to 1.00, please refer to images below
for impacts on different settings of Refraction Glossiness.
Images below set the Refraction IOR to 1.55, you can see the Glossiness changes
gradually from 0.85. It changes rapidly between 0.80 and 0.75. When the setting
for Refraction Glossiness remains the same, different Refraction IOR will change
the Glossiness of the object.
Just like the intensity of the Fog Multiplier affects its transparency, the
Refraction Glossiness in thicker object becomes more obvious.
Image below shows the influence of Refraction Glossiness material to objects
behind it. Objects further away become very blurry.
Shadows of refractive materials
There is an Affect Shadow option to the right hand bottom corner of the
Refraction dialog box, default is unchecked. When checked, the color of the
transparent object will affect its shadow and it's not black anymore. The shadow
also becomes more depth as well.
It is recommended to always have Affect Shadows checked, as it produces a
more realistic effect.
Images below show the difference with and without the Affect Shadows checked.
Double-sided material
Under Options of each material, you will find this Double-sided selection.
Default setting is checked. This option is particularly important for
transparent material. When this option is unchecked, light enter to the inside
surfaces will not be rendered and show up black. The reason to have this option
is that sometimes you may want to uncheck this option when render object with
translucent material (see next page) in order to get the right texture.
Unless you want to create some special effects, please have this option
checked.
The double sided option will not have any affect on the shadows of the
object.
Translucent material
We've talked about changing the Diffuse color to get the degree of
transparency we want to create before. White means 100% transparent, black means
100% opaque. You can create translucent materials with colors anywhere between
white and black. But now we want to introduce a different translucent material.
It is related to special light absorption materials.
Open file: Translucency.3dm and render
it, you will get image like below. You will see that colors where
partitions meet the outside box and at the base of the box are darker. This is
because the thickness of the object changes and the light travel distance
changes also. So the degree of light absorption varies. To create this kind of
material, you have to check the Translucency option under the Refraction. The
second image below is the rendered result for Layer 02.
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Check the Translucent box under Translucency first. Thickness is for control
of light pass through the object, the unit for this is unclear. Keep these three
settings as default. Other items required to change include:
1. Double-Sided must be unchecked so the light can get through to the inside
of the object. This setting is extremely important.
2. Change the IOR to 1.
3. Decrease the Refraction Glossiness to a value below 1.
4. Do not use white color for the Transparency because that will turn the
object to completely transparent and become dark after rendered due to absorb
too much light. Do not use black color, either. That will not allow light get
through the object at all. Pick a color anywhere between Val 80~150 will give
you the best result.
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Many rendering engines use Sub-Surface Scattering (SSS) to create this kind
of material. This material is good for creating things like: wax, skin, milk,
cheese, plastic and jade which all have a little translucency in it.
Translucency is created by absorbing light to the object's surface so the
color of the object will show up a little darker than its original color. If you
still think that it's too dark even though the original color is set to the
highest Val 255, the best way to fix it is increasing the intensity of your
light in the scene.
Below are some examples.
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