mental ray Architectural and Design Visualization Shader Library

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28 2 Architectural Materialtexture map to steer the angle:anisotropy rotation values of 0.0 (left), 0.25 (center) and textured (right)Note: When using a textured anisotropy rotation it is important that this texture isnot anti-aliased (filtered). Otherwise the anti-aliased pixels will cause local vortices in theanisotropy that appear as seam artifacts.For values of 0 or above, the space which defines the “stretch directions” of the highlights arederived from the texture space set by anisotropy channel 10 .anisotropy channel can also have the following “special” values:• -1: the base rotation follows the local object coordinate system.• -2: the base rotation follows the bump basis vectors• -3: the base rotation follows the surface derivatives• -4: the base rotation follows a vector placed in state>tex prior to calling mia materialSee also “brushed metal” on page 58 in the tips section.2.5.6 BRDFAs explained in the introduction on page 9 the materials reflectivity is ultimately guided bythe incident angle from which it is viewed.10 Note that deriving the anisotropy from texture space only creates one space per triangle and may causevisible seams between triangles.
2.5 Detailed Description of Material Parameters 290 degree (green) and 90 degree (red) view anglesThere are two modes to define this BRDF curve:The first mode is “by IOR”, i.e. when brdf fresnel is on. How the reflectivity depends onthe angle is then solely guided by the materials IOR. This is known as Fresnel reflections andis the behavior of most dielectric materials such as water, glass, etc.The second mode is the manual mode, when brdf fresnel is off. In this mode thebrdf 0 degree refl parameter defines the reflectivity for surfaces directly facing the viewer(or incident ray), and brdf 90 degree refldefines the reflectivity of surfaces perpendicularto the viewer. The brdf curve parameter defines the falloff of this curve.This mode is used for most hybrid materials or for metals. Most material exhibit strongreflections at grazing angles and hence the brdf 90 degree refl parameter can generally bekept at 1.0 (and using the reflectivity parameter to guide the overall reflectivity instead).Metals tend to be fairly uniformly reflective and the brdf 0 degree reflvalue is high (0.8to 1.0) but many other layered materials, such as linoleum, lacquered wood, etc. has lowerbrdf 0 degree refl values (0.1 - 0.3).See the tips on page 48 for some guidelines.2.5.7 Special Effects2.5.7.1 Built-in Ambient OcclusionThe built in Ambient Occlusion (henceforth shortened to “AO”) can be used in two ways.Either it is used to enhance details and “contact shadows” in indirect illumination (in whichcase there must first exist some form of indirect illumination in the first place), or it is usedtogether with a specified “ambient light” in a more traditional manner. Hence, if neither
Page 1 and 2: mental ray Architectural and Design
Page 3 and 4: Table of Contents1 Introduction 11.
Page 5: Table of Contentsix3.8.3 Examples .
Page 9 and 10: Chapter 2Architectural Material2.1
Page 11 and 12: 2.2 Fundamentals 52.2.1.1 A Note on
Page 13 and 14: 2.3 Features 7Hence, when using GI:
Page 15 and 16: 2.3 Features 9The rules are as foll
Page 17 and 18: 2.3 Features 11In the real world
Page 19 and 20: 2.3 Features 13Used alone, an AO sh
Page 21 and 22: 2.3 Features 152.3.7 Performance Fe
Page 23 and 24: 2.4 Quick Guide to the Material Par
Page 25 and 26: 2.5 Detailed Description of Materia
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Page 55 and 56: 2.6 Tips and Tricks 49• For extre
Page 57 and 58: 2.6 Tips and Tricks 51Diagram for g
Page 59 and 60: 2.6 Tips and Tricks 53There is one
Page 61 and 62: 2.6 Tips and Tricks 55• Glass-Liq
Page 63 and 64: 2.6 Tips and Tricks 57Enjoy the tro
Page 65 and 66: 2.6 Tips and Tricks 59Many small ad
Page 67 and 68: Chapter 3Sun and Sky3.1 Introductio
Page 69 and 70: 3.4 Common Parameters 633.3 Importa
Page 71 and 72: 3.5 Sun Parameters 65• saturation
Page 73 and 74: 3.6 Sky Parameters 67light"sun",# T
Page 75 and 76: 3.6 Sky Parameters 69• sun direct
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3.9 Photometric Lights 833.9 Photom
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3.9 Photometric Lights 85• When i
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88 4 Camera- and Exposure EffectsAl
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90 4 Camera- and Exposure Effects4.
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92 4 Camera- and Exposure Effects1,
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94 4 Camera- and Exposure EffectsTh
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96 4 Camera- and Exposure Effectscr
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98 4 Camera- and Exposure EffectsEv
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100 4 Camera- and Exposure EffectsS
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Chapter 5General Utility Shaders5.1
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5.2 Environment Blur 105replaced by
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5.2 Environment Blur 107But what is
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5.2 Environment Blur 109Glossiness
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5.3 Light Surface 111An example of
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5.3 Light Surface 113the other two
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5.3 Light Surface 115Complex geomet
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5.3 Light Surface 117Another exampl
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