Advanced materials.pdf

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p://www.alzhem.com/_support/_tutorials/tutorial06_en.htm[01/05/2013 9:44:23]

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This tutorial is COPYRIGHT by J os Mara Andrs Martn (ALZHEM)The total or partial reproduction of this tutorial by any means is prohibited to third parties without prior written authorization from J os Mara Andrs Martn (ALZHEM)

Advanced Mater ials

J ob finished! But... What happened? We have made a good model, worked in the illumination setup... butthere is anything sating this is a C.G. picture. Many times the problem is we want to see the first G.Irender and we don't have care of our materials.

In this tutorial, we will create many basic materials very useful explaining step by step what to do. Thismaterials are plastic, wood, chromed metal, glass, metallic paint, water and velvet.We will use VRay, but this tutorial can be followed by another render engine users, as finalRender, Brazilor MentalRay.

To get advanced of this tutorial, we must know many concepts:

Color: chromatic shade of an object. We can use a only color, or a bitmap.Specular highlights : bounce of the light come from a luminous emitter. The rougher (surface) therefracter (light over it). The most used are the Blinn (plastic, wood, almost every material),Anisotropic (CDs, or similar) and Multi-Layer (more attractive).Opacity: level of transparency of an object. It can be configured with a value (%) or with a bitmap.Reflexion : feature of many object to reflect the light. It can be set up with a percentage, and theglossiness.Refraction : feature of the transparent materials or translucent to change the trajectory of thephotons which pass through it, distorting the image seen through them. The amount of variation ofthe trajectory is determined by the Index of Refraction (IOR).

Once explained this concepts, and before to start the "nice" part, we are going to see how to do a veryuseful effect which we will use in almost all the materials: the "Fresnel reflection" .

The "Fresnel reflection" is a kind of bounce of the light which only works in the perpendicular parts ofthe objects (with the camera). Is the realest for plastics, glasses, porcelain, etc.

To do this effect is more or less easy:

1. Add to the "Reflection" a "Falloff" map.
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2. Select as kind of "Falloff" the "Fresnel" one.

3. Do "clic" on the "NONE" button of white color, and add there "VRayMap" . If we use another render

engine we will use the respective raytrace map, or the "Raytrace" for the scanline render.


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4. The "Fresnel" reflect is done. If we want to blur the reflect, we only need to turn the "Glossy" checkbox on, and try with differents values of the Glossiness.


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Once seen this, we are prepared to begin with our materials.

Matte plastic (Standard Material)

1. Assign a color simple (Diffuse) or a picture (Bitmap). This will be the color of ourobject.

2. Use a white specular color, with a low intensity (Specular Level = 20 - 30) and diffuseenough (Glossiness = 10 - 20).

3. To improve the final look we can use a "Fresnel" reflect very blurred.


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Polish plastic (Standard Material)

1. Assign a color simple (Diffuse) or a picture (Bitmap). This will be the color of ourobject, as in the matte plastic

2. Use a white specular color, with a high intensity (Specular Level = 200 - 500) and verysharp (Glossiness = 85 - 95).


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3. Apply a clear "Fresnel" reflect.


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Wood (Standard Material)

1. Use a picture (Bitmap) as the image of the wood we wanted, or the procedural materialof the MAX called "Wood". Is adviced to use a bitmap because of the realism of this one(though if we get a good procedural we won't need to add a mapping to the woodenobjects. In both cases, is used to be needed a desaturation (use as "Diffuse" a grey color

(128,128,128) and change the percentage of the bitmap (or procedural) to 80 - 90%).2. Change the color of the specular to amber or similar, of low intensity (Specular Level =

20 - 30) and very widespread (Glossiness = 10 - 20). It can be improved with a Multi-Layer specular, as in the example.

3. We can simulate the bump copying the "Diffuse" map to the "Bump" box. The intensitywill be changed depending on the contrast of the "Diffuse" map. Try different levels ofbump until it works.

4. If the wood is recent varnished, we will use a sharp "Fresnel" reflect with a 70 - 90% of

intensity. If the wood is matte or if the object is old, we can use the "Glossiness" option ina "Fresnel" reflect with a 50 - 70 % of intensity.


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Chromed metal (Standard Material)

1. To get a not too bright reflect, we must use a dark "Diffuse" color (dark grey or black).

2. The specular will be white and very sharp (Glossiness = 85 - 95) and with a hugeintensity (Specular Level = 200 - 500). It can be enhanced with the Multi-Layerspecular, as it is in the example.

3. Apply a common reflection (not Fresnel) set to 100%.

NOTE: the "quality" of the chromed depends COMPLETELY on the environment thatsurrounds the object. The richer environment (a finished 360 complete and full scene), the

better result.


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Glass (VRayMtl Material)

We are going to create this material using the "VRayMat" of the VRay render engine. Doingthat we will see the facility of using this new material.

1. In the "Diffuse" color select a very dark color (better black), to avoid the bright reflecfts.


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2. Change the black color of the "Reflect" (no reflect) with white (maximun reflection).Activate the "Fresnel reflections" (easier than standard way seen before).

3. The refraction works exactly the same way of reflection. Change the black color (norefraction) with white (maximun refraction).

VERY IMPORTANT: to get a "real" glass, we must use the specific Index Of Refraction(IOR) of the glass (1,52 more os less). If we use another value the effect will be wrong.

Also, we can do variations of this glass as the following ones:

Tinted glass: the glass can be tinted with the color we want. We only need to do some test toget the exactly tint effect, due to the thickness of the object. To get this, change the whitecolor of the Fog color with the desired and change the Fog multiplier until we get the

wanted tint amount.


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Not flat glass: this is a very interesting glass, and can be used in screens, windows, etc. Weonly need to use a bump map. In this case, it's made with a noise map in the "Bump" button.


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Acid glass : it could be a variation of the last material, but with a very small size of noise. Todo this we don't need a bump map, because the VRayMat has an option to get this effect. Weonly need to activate the Glossiness value from 1 (perfect glass with no distortions) to the

value we want (0,8 is the value of the example). The smoothness of this effect depends on theSubdivs value: the higher the smoother (but it increase the render time).


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Metallic paint (Standard Material)

1. In the Diffuse color button add a Falloff map (due to the effect of the real metallicpaint) not a basic color. Once into the "Falloff" options, change the first color with thedesired color of the object (blue, red...) and the second one with a very darker version of


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the first color, or even black.

2. To enhance the specular shine use a Multi-Layer one (it is a mix of two specularshines). The first specular must be a white one, very intense (Specular Level = 300 -500) and very sharp (Glossiness = 90 - 95). The second specular must be of the color ofthe object, but brighter, and diffuse enough (Glossiness = 15 - 30), and its intensity willbe controlled by a Celullar, Noise or similar map, but always using a very small size.

This way we can get the "grease" effect.

3. Apply a Fresnel reflect (in the metallic paint case, we can use a 20% commonreflect).


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Water

At the begining, we must think about wwhat kind of water we need, transparent water (if weare going to see what is under the sea), or opaque one (if we only want it refrecl). If we needtransparent water we will use a "VRayMtl" material due to the possible problems with theshadows if we use a "Standard" one.

Transparent water(VRayMtl Material)

1. To avoid the bright "Fresnel" reflects we will use the black as the "Diffuse" color.

2. Change the black of the "Reflect" box to white and check the Fresnel reflection on.

3. Also, modify the black box of the "Refract" to white (total refraction). The Index OfRefraction (IOR) must be 1,33.

4. We get the relief using a Noise map ("Regular" or "Fractal" as we want).

NOTE: is very important to activate the Affect Shadows checkbox of the VRayMtlmaterial to process correctly the color.


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(changing the size of the "Noise" map)

Opaque water(Standard Material)

1. The Diffuse color will be a lightly desaturated blue (relatively next to grey) and darkenough (the blue of the example is RGB: 28, 48, 58).

2. A nice specular shine is made using the Multi-Layer one. The primary specular will

be a white one, of a high intensity (Specular Level = 200 - 500) and very sharp(Glossiness = 85 95). The secondary specular will be light blue, with not too muchintensity (Specular Level = 20 - 35) and very diffuse (Glossiness = 20 30).

3. Use a Fresnel (remember the "Falloff" technic) reflect in the Reflect button.


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VERY IMPORTANT: similar to the chromed effect, the water quality depends directly on theenvironment. If we can't get a nice reflect, we could use a bitmap to get a reflect different tothe real one. You can get this with the "Reflection/refraction etc environment" - "OverrideMAX's" VRay's option in the render engine configuration window.

Velvet (Standard Material)

1. The key of this material is it's color, because the lack of specular shine, reflect orsimilar. The appropiate effect is produced by the Falloff material applied to the Diffusebutton. The upper color of the "Falloff" material will be garnet (in this case), and the lowerone pink (not pastel pink).

2. Though the effect would be almost achieved, we could improve it adding a little "Noise"to the "Bump". It must be very little and fractal.


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Selection of the original table of J on Reynolds aboutReflect and Refract values


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MaterialReflectance

valuesMaterial

Index of Refraction

(IOR)

Pure aluminum /polished 65 - 75 % Air 1,0002926

Matte aluminum 55 - 75 % Alcohol 1,329

Steel 25 - 30 % Amber 1,546

INOX 80 - 90 % Aquamarine 1,577

High polished copper 60 - 70 % Diamond 2,417

Polished tin 67 - 75 % Emerald 1,56

Light oak /polished/ 25 - 35 % Glass 1,51

Dark oak /polished/ 10 - 15 % Hydrogen (gas) 1,000140White paper 70 - 80 % Ice 1,309

Granite 20 - 25 % Metanol 1,329

Polished marble 30 - 70 % Naylon 1,53

Light stucco 40 - 45 % Oxigen (gas) 1,000276

Dark stucco 15 - 25 % Oxigen (liq) 1,221

Concrete 20 - 30 % Plastic 1,460

Bricks red/new 10 - 15 % Quartz 1,544

Glass 5 - 10 % Ruby 1,760

Silver mirror 80 - 88 % Tiger eye 1,544

High polished mirror 92 - 95 % Topaz 1,620

White tiles 75 - 80 % Water (gas) 1,000261

White enamel 65 - 75 % Water (20 C.) 1, 33335White lacquer 80 - 85 % Zircon 1,777 1,987

If you like this tutorial, please write a comment or a suggestion in the "Guest Book" section.

Thanks
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