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94 4 Camera- and Exposure EffectsThe “Sunny 16” resultThe settings we used abide by the “Sunny 16” rule in photography; for an aperture of f/16,setting the shutter speed (in fractional seconds) equal to the film speed (as an ISO number)generates a “good” exposure for an outdoor sunny scene. As we can see, indeed, the outdoorarea looks fine, but the indoor area is clearly underexposed.In photography, the “film speed” (the ISO value), the aperture (f number) and shutter timeall interact to define the actual exposure of the camera. Hence, to modify the exposure youcould modify either for the “same” result. For example, to make the image half as bright, wecould halve the shutter time, halve the ISO of our film, or change the aperture one “stop” (forexample from f/16 to f/22, see page 91 for more details).In a real world camera there would be subtle differences between these different methods, butwith this shader they are mathematically equivalent.f/8 f/4Clearly the f/4 image is the best choice for the indoor part, but now the outdoor area isextremely overexposed. This is because we have the burn highlights parameter at 1.0,which does not perform any compression of highlights.burn highlights = 0.5 burn highlights = 0.0
4.1 Tone Mapping 95The left image subdues the overexposure some. The right image is using a burn highlights ofzero, which actually removes any overexposure completely. However, this has the drawbackof killing most contrast in the image, and while real film indeed performs a compression of theover-brights, no film exists that magically removes all overexposure. Hence, it is suggested tokeep burn highlights small, yet non-zero. In our example we pick the 0.5 value.Real cameras have a falloff near the edges of the image known as “vignetting”, which issupported in this shader by using the parameter of the same name:vignetting = 5 vignetting = 11The image on the right is interesting in that it “helps” our overexposed outdoors by the factthat it happens to be on the edge of the image and is hence attenuated by the vignetting.However, the left edge turns out too dark.We will try a middle-of-the road version using a vignetting of 6 and we modify theburn highlights to 0.25 and get this image:vignetting = 6 burn highlights = 0.25This image is nice, but it really lacks that feel of “contrast”. To help this we play with thecrush shadows parameter:
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mental ray Architectural and Design
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Table of Contents1 Introduction 11.
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Table of Contentsix3.8.3 Examples .
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Chapter 2Architectural Material2.1
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2.2 Fundamentals 52.2.1.1 A Note on
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2.3 Features 7Hence, when using GI:
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2.3 Features 9The rules are as foll
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2.3 Features 11In the real world
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2.3 Features 13Used alone, an AO sh
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2.3 Features 152.3.7 Performance Fe
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2.4 Quick Guide to the Material Par
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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
Page 77 and 78: 3.8 Sky- and Environment Portals 71
Page 89 and 90: 3.9 Photometric Lights 833.9 Photom
Page 91: 3.9 Photometric Lights 85• When i
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Page 109 and 110: Chapter 5General Utility Shaders5.1
Page 111 and 112: 5.2 Environment Blur 105replaced by
Page 113 and 114: 5.2 Environment Blur 107But what is
Page 115 and 116: 5.2 Environment Blur 109Glossiness
Page 117 and 118: 5.3 Light Surface 111An example of
Page 119 and 120: 5.3 Light Surface 113the other two
Page 121 and 122: 5.3 Light Surface 115Complex geomet
Page 123: 5.3 Light Surface 117Another exampl
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