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Vray Materia Materials ls
I will release my “Creating Vray Materials” video Materials” video training
next week.
Originally I planned to make this theory part available only
for those who buy the video, but I’ve decided to share it with
everyone, so enjoy!
slow, noisy and non-realistic results. VRay is designed to be
used with it’s native shaders, so that is what we are going to do.
Now let’s look at the first section – Diffuse.
Think of Diffuse as the base color of the object. If you see a
tomato, you can instantly tell it’s red. This means that red is the
Diffuse color. It is a bit more complicated for very reflective or
very refractive objects, but we will look at those later.
VRayMtl allows you to choose a simple color as the Diffuse or
use a Map. You can use any Bitmap or Procedural Map in the
Map slot.
Here is an example.
The Roughness parameter can “flatten” the color transitions.
You can use it to make your material appear dusty and flat.
Here is an example with the same green material at 0, 0.5 and
1.0 Roughness.
Next section is Reflection
As the name suggests, this section deals with the reflective
properties of the material. Most real world objects are reflective.
Look at these photos of chrome and brick for example.
The reflections of the chrome are very strong and sharp, you can
instantly recognize it as a reflective surface. But what about the
brick? It might look that it’s not reflective at all, but in fact the
reflections are just weak and very very blurred. The only objects
that don’t reflect any light are the black holes
mind when creating the materials.
Keep this in
makes it fully reflective. All the gray scale values between
increase or decrease the reflection strength. The color sliders in
3Ds Max go from 0 to 255, this means that if you want to make
a material that reflects 50% of the light that hits it, you need to
set the value of the reflections to 128. Here is an example at 0,
128 and 255. Notice how the third image has lost all the Diffuse
color and is only showing the reflections. Reflections make the
base color weaker as they get stronger. The Energy Preservation
law doesn’t allow realistic materials to reflect more light than
they receive. This means that If the material has 0% reflections,
it shows 100% of the Diffuse color. If the material has 30%
reflections, the Diffuse color is weakened to just 70%, and so on.
Think of the reflections as a layer on top of the Diffuse, together
they create the final image.
The Diffuse color for all the examples is 128 gray. Notice how
the Reflect color changes the look of the Diffuse. This color
change happens because VRay adheres to the Energy
Preservation rule. If the material reflects the red colored light,
the red color is subtracted from the Diffuse and only green and
blue are left. This behavior can sometimes make it difficult to
predict the final result, this is why you can change the Energy
Preservation mode in the material options. If you choose
Monochrome, only the reflections will be colored and the
Diffuse color will be left unchanged.
Next up is Reflection Glossiness. This is the parameter that
controls how sharp/blurred are the reflections. Some real world
objects, like polished metal, mirror, chrome, have very sharp
reflections, while other materials, such as wood, concrete,
plastic, etc., have blurred reflections. You can adjust the
Reflection glossiness from 0 to 1 (completely blurred to
perfectly sharp). For most materials you will not need to lower
the glossiness below 0.3. You should always use blurred
reflections with caution, do not lower the glossiness more than
necessary, as this will cause more noise in your image, you can
get rid of it by increasing the Subdivs, but it will take a toll on
the rendertime. Here are some basic examples of how the
glossiness works.
Notice the noise introduced into the image. You can clean it up
with the Subdivs parameter, increasing it will make reflections
smoother at the cost of render time. Notice how the render time
has increased 3.5 times if you compare the third and first
images. 16 is a good choice for decent result without too much
waiting. You can use the subdivs parameter to find a balance
between time and quality.
Next up is the Fresnel parameter. You might have heard that all
real world materials feature Fresnel reflections, but what does it
actually mean? Fresnel changes the reflection strength
depending on the viewing angle. General rule is that reflections
are weaker if the surface is facing you perpendicularly and
increase in strength as the surface approaches parallel position
relative to your viewing angle. Here are some real world
examples where you can see this effect in action. The marble,
car and wall surfaces are much more reflective when they are
more parallel to the viewing angle.
And here is how the Fresnel IOR or Index of Refraction works.
Use only values from 1.01 up, lower values are not physically
correct for normal materials. Increasing the IOR changes the
relationship between the angle of the surface and reflection
strength, look at the examples.
As a general guideline, here are the Reflect IOR values for some
common object types:
water 1.33
plastic 1.45
glass 1.5-1.8
diamond 2.4
compound materials like wood, stone, concrete etc 3-6
metals 20-100
see, 6 reflections are plenty for this scene. Other scenes with
more reflective surfaces might need a larger value.
First parameter that controls the refractions is Refract color. As
before, it goes from black (no refractions) to white (full
refractions) and everything in between is a mix between Diffuse
and Refraction.
Here are some examples with a black material. I recommend
using black diffuse color [1;1;1] for most of the transparent
materials and adjust the overall color with Refract color and Fog
color.
You can use a color, bitmap or procedural map in this slot as
well.
Refraction glossiness. Just like with the reflections, you can
change how blurry are the refractions. This effect is great for
frosted glass or any other rough surface that lets through the
light but distorts it along the way.
This one increases render times and noise a lot so be careful
with it. No need to go lower than 0.6 for most materials.
To clean up the noise, we need to increase Subdivs parameter.
As you can see, getting a clean result comes with a huge cost.
The render time for the last image is almost 7 times longer than
with the default value. It is also 15 times longer than not using
blurred refractions at all! So try to minimize the blurred
refractions if you need fast renders.
In the real world light changes it’s angle as it travels between
objects of different density, thus the surface ‘refracts’ the light.
IOR value of 1 let’s the light through without bending it, as the
IOR value increases, so does the angle at which light is
refracted. Look at these examples.
Index of Refraction has been calculated for many materials, so
you don’t need to guess. You can find various IOR tables on the
internet. Here is one of them:
Acetone 1.36
Actinolite 1.618
Agalmatoite 1.550
Agate 1.544
Agate, Moss 1.540
Air 1.0002926
Alcohol 1.329
Amber 1.546
Amethyst 1.544
Crystal 2.00
Diamond 2.417
Emerald 1.576
Ethanol 1.36
Ethyl Alcohol 1.36
Glass 1.51714
Glass, Albite 1.4890
Glass, Crown 1.520
Glass, Crown, Zinc 1.517
Glass, Flint, Dense 1.66
Glass, Flint, Heaviest 1.89
Glass, Flint, Heavy 1.65548
Glass, Flint, Lanthanum 1.80
Glass, Flint, Light 1.58038
Glass, Flint, Medium 1.62725
Gold 0.47
Ice 1.309
Ivory 1.540
Jade, Nephrite 1.610
Jadeite 1.665
Lead 2.01
Malachite 1.655
Methanol 1.329
Moonstone, Albite 1.535
Nylon 1.53
Onyx 1.486
Opal 1.450
Oxygen (gas) 1.000276
Oxygen (liq) 1.221
Pearl 1.530
Plastic 1.460
Plexiglas 1.50
Polystyrene 1.55
Quartz 1.544
Quartz, Fused 1.45843
Rock Salt 1.544
Rubber, Natural 1.5191
Ruby 1.760
Sapphire 1.760
Silicon 4.24
Steel 2.50
Tiger eye 1.544
Topaz 1.620
Tourmaline 1.624
Turpentine 1.472
Turquoise 1.610
Water (gas) 1.000261
Water 35′C (Room temp) 1.33157
Zirconia, Cubic 2.170
Max depth works just like with the reflections. The default value
is usually fine, but for scenes with large amount of refractions,
you should increase it.
Next parameter is Fog Color. It is great if you want to tint the
glass in a realistic way. Using the Fog color makes thinner parts
lighter and thicker parts darker. You can use the Fog multiplier
value to adjust how strong is the tint. I suggest using colors with
less than 255 lightness and saturation for realistic results.
You can control the relationship between object thickness and
Fog intensity by using the Fog Bias value. Look at the examples
to see how it works. Negative values make the tinting stronger
and color transitions more extreme, while positive values make
the fog smoother and weaker. Use it together with fog multiplier
to get the effect you need.
The biggest drawback of the Fog color is that you can not use a
map in this slot, this means you can only use a single color. If
you want to create a stained glass material or glass with
multiple colors, you will have to do that by using the Refract
color and not the Fog. It is, however, great for those single-
colored materials and much more realistic than simply changing
the Refract color.
Dispersion also increases the render time.
First is the BRDF model. This parameter affects how the
specular highlights of the material are calculated. VRay offers 3
options: Phong, Blinn and Ward. Phong has the sharpest
highlights, Blinn is a bit more blurred and Ward is even softer.
Blinn is the default value and it is fine for most materials, for
metals you will want to use the Ward model.
Anisotropy allows you to create stretched highlights. In real
world these are most commonly seen on brushed metal surfaces
with long, parallel ‘scratches’. Anisotropy allows you to fake this
by stretching and rotating the highlights as you like.
This example shows how changing the Anisotropy value
changes the speculars. Negative values stretch them highlights
horizontally while positive values stretch them vertically.
And finally you can change the reference axis for even more
control.
Next comes the Maps section of the material. This is a
convenient list of all the slots you can assign bitmaps or
procedural maps to.
There are some important properties of the material that can
only be accessed through this section. These are Bump, Displace
and Opacity.
Let’s look at the Bump and Displace slots first.
Both of these slots allow you to assign a bitmap or procedural
map to simulate unevenness and deformation of the objects
surface. Bump does so without changing the overall geometry of
the object, but Displace actually subdivides and deforms the
object during rendering. The deformations work like this –
middle grey [128;128;128] of the map does not change anything
on the object, darker values push the surface inwards while
lighter values pull it out. The further this value is from medium
gray, the stronger is the effect. Color of the map is not taken into
account and only the lightness value is used.
Last map we are going to look at is the Opacity map. It works
very simple. Pure white value is used for the non-transparent
parts of the material and pure black is for completely invisible
parts of the material, everything in between is more or less half
transparent. It is great if you need to simulate stuff like tree
leaves or lace fabric without using a large amount of polygons.
Here is an example using the same map as in the Bump
samples.
The two next segments of VRayMtl are Reflect Interpolation
and Refract Interpolation. They are supposed to be a quicker
way for calculating blurred reflections and refractions, but I will
not be covering those, as I have often found troubleshooting the
issues/glitches that can appear from them take longer time than
rendering non-interpolated materials.
This wraps up the basic VRayMtl, it already allows you to create
90% of the materials you will encounter in your work. There
are, however, some special cases where other materials are
better suited.
Let’s look at the VRayBlendMtl. It is the perfect tool for making
compound materials.For example, if you need to create a black,
shiny surface with blurred gold spots, it is way easier to create
two materials and blend them together than hand painting all
the different maps you would need to achieve this effect in a
single VRayMtl.
base material and finally pure black doesn’t show any coat
material at all.
Each next coat layer treats everything above it as a single
material, if you have a base material and 2 coat materials at
50%, the result is 0.5(0.5base+0.5_1st_coat)+0.5_2nd_coat.
In this example I’ve added a second coat layer with pure green
diffuse color, if all 3 parts would be used equally, the resulting
color should be white (RGB at equal values result in grayscale
color), but it is instead a 50/50 mix of purple and green.
You can use up to 10 material in a blend (if you then create a
new VRayBlendMtl and keep the filled one as sub-material, you
can add 9 more materials, repeating this procedure gives you
unlimited amount of slots). Here is a somewhat more complex
example of a 4 material blend.
I am sure you now see the potential of VRayBlendMtl. I will
show you some practical examples on how to use it in the
videos.
Let’s move on to the next material type – VRayFastSSS2. The
letters SSS stand for Sub-Surface Scattering, another common
name is Translucency. This effect happens when light rays don’t
go straight through the object, but are scattered in multiple
directions when inside, this does not allow you to see through
the object, but you can see the light inside it. Unlike refraction
glossiness which scatters light rays at the surface, SSS does this
inside the object. This makes some interesting lighting effects,
the light penetrates the object and lights it from within. Some
real world examples are: flesh, milk, marble, jade, fruit, wax etc.
Look at these photos to see what I’m talking about.
surface while VRayfastSSS2 is more illuminated. The effect is
very subtle though.
Next parameter, SSS prepass, controls the accuracy of the
scattered light. Lower values give blurrier results, while higher
values give a more precise rendering, the precision comes with
an increased render time. For production renders, I suggest
using values of -1 to 1.
Fast SSS allows you to set the IOR as well. Most water based
materials like skin, milk, juice, plants have IOR of ~1.3, for
stone type materials 1.5-1.7 is more suitable.
You can also use the built-in presets to quickly create some
common materials, these are:
Skin (brown)
Skin (pink)
Skin (yellow)
Milk (skimmed)
Milk (whole)
Marble (white)
Ketchup
Cream
Potato
Spectralon
Water (clear)
First is the Overall color. This color allows you to change the
color of the whole material (the surface and the inside).
Look at the examples to see how this color changes the look of
the default VRayfastSSS2 material.
Next is the Diffuse color and Sub-Surface color. First one
controls the outer surface, second one controls the inside of the
object. This works somewhat different than VRaymtl. By
default, VRayfastSSS2 only uses the sub-surface color and
scatter color as the main sources of pigment. You can assign a
diffuse color and increase the diffuse amount to mix it with
those two colors. It is a bit hard to explain, I’ll show you an
example. Here I have assigned a Red Diffuse color and a Blue
sub-surface color. With the default setting of 0 Diffuse is not
seen at all, when I increase it to 0.5 it is a 50% mix with the blue
and finally, when I set it at 1, there is no more translucency and
only the red diffuse color is seen.
Ok, let’s look at the Scatter color now. The lightness of this color
affects how strong is the scattering effect. It get’s stronger from
black to white, as usual.
I’m using a simple grey material with red sub-surface color in
this example.
You can also use a saturated color in this slot to give a tint to the
object. It work’s best if you use a color that is close to the sub-
surface color. It also tints in the opposite direction, sounds
weird, I know. What it means is if your sub-surface color is red
and you set the scatter color as orange, the actual tint will be to
the opposite direction of the hue scale – purple. If you use
purple, the tint will be orange. Look at the pictures to see it in
action. The effect is subtle, but sometimes it’s just what is
needed!
highlights just like with the VRaymtl – by changing the
glossiness value.
There are 3 possibilities you should use depending on the
material you are trying to create.
Simple mode is best for materials where the light doesn’t go too
deep, best examples are skin, plastic.
Refractive mode is great for materials that are very translucent
but at the same time quite opaque (marble, milk)
Refractive (raytraced) mode is for more transparent materials,
this also creates nice refractions and transparent shadows. Use
it for materials like glass, water, crystals.
