The RenderMan Interface - Paul Bourke

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Reflected ray color Transmitted ray color External Volume Internal Volume Light Sources Attenuated reflection color Attenuated transmission color Light colors Displacement Displaced surface Surface Surface color Atmosphere Apparent surface color Figure 9.2: Shader evaluation pipeline 111
Section 10 RELATIONSHIP TO THE RENDERMAN INTERFACE The Shading Language is designed to be used with the RenderMan Interface described in Part I of this document. This interface is used by modeling systems to describe scenes to a rendering system. Like most graphics systems, the RenderMan Interface maintains a current graphics state. This state contains all the information needed to render a geometric primitive. The graphics state contains a set of attributes that are attached to the surface of each geometric primitive. These shading attributes include the current color (set with RiColor and referred to as Cs) and current opacity (set with RiOpacity and referred to as Os). The geometric primitive also contains a current surface shader (RiSurface) and several volume shaders: the current atmosphere shader (RiAtmosphere), current interior shader (RiInterior) and a current exterior shader (RiExterior). All geometric primitives use the current surface shader for computing the surface shading at their surfaces. Light directed toward the viewer is attenuated with the current atmosphere shader. If the surface shader of a primitive causes rays to be traced (with the trace() function), the ray color will be attenuated with either the current exterior shader or current interior shader, depending on whether the traced ray is in the direction of, or opposite to, the surface normal. The graphics state also contains a current list of light sources that contains the light sources that illuminate the geometric primitives. Light sources may be added to or removed from this list using RiIlluminate. Light sources can be attached to geometric primitives to define area light sources (RiAreaLightSource) or procedurally define their geometric properties (RiLightSource). The current area light source contains a list of geometric primitives that define its geometry. Defining a geometric primitive adds that primitive to this list. The graphics state also maintains the current transformation that is the transformation corresponding to the modeling hierarchy. The graphics state also contains a current displacement shader (RiDisplacement) and an imager (RiImager). The RenderMan Interface predefines standard shaders for light sources, surfaces, and volumes. These standard shaders are available in all rendering programs that implement the RenderMan Interface, even if some algorithmic limitation prevents them from supporting programmable shaders. Standard and implementation-dependent shaders should always be specified in the Shading Language, even if they are built in. The predefined shaders provided by the Shading Language are listed in Table 10.1, Standard Shaders. There is also a null shader that is used as a placeholder. Shading Language definitions for these shaders are given in Appendix A. 112
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The RenderMan Interface Version 3.2
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TABLE OF CONTENTS List of Figures L
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12.1 Surface Shaders . . . . . . .
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Section I DIFFERENCES BETWEEN VERSI
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LIST OF TABLES 4.1 Camera Options .
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PREFACE This document is version 3.
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Section 1 INTRODUCTION The RenderMa
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created using this language. This l
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Depth of Field The ability to simul
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typedef RtPointer typedef RtPointer
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RiContext (ctx1); ... There is no R
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Section 3 RELATIONSHIP TO THE RENDE
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through the interface. Any place wh
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RtContextHandle RiGetContext ( void
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RiWorldBegin (); ... RiColor (...);
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Camera Option Type Default Descript
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ottom top left right Screen Window
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EXAMPLE RiFrameAspectRatio (4.0/3.0
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not support the special projection
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This procedure sets the times at wh
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Output depth values are the camera-
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A particular renderer implementatio
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Renderers may additionally produce
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The number of color components, n,
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RiAttributeBegin () RiAttributeEnd
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RIB BINDING Color c0 c1... cn Color
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An area light source is defined by
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The sequencenumber is the integer l
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4.2.5 Displacement shading The grap
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SEE ALSO RiExterior RiAtmosphere Ri
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Matte onoff EXAMPLE RiMatte (RI TRU
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object foo2 will be drawn when the
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the exterior is the region adjacent
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RiIdentity ( ); SEE ALSO RiTransfor
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RiScale ( RtFloat sx, RtFloat sy, R
Page 71 and 72: 4.3.2 Transformation stack Transfor
Page 73 and 74: Section 5 GEOMETRIC PRIMITIVES The
Page 75 and 76: Information Name Type Class Floats
Page 77 and 78: No checking is done by the RenderMa
Page 79 and 80: 5.2 Patches Patches can be either u
Page 81 and 82: U V 0 1 2 3 12 13 14 15 4 5 6 7 8 9
Page 83 and 84: 10 x 7 Aperiodic Bezier Bicubic Pat
Page 85 and 86: SEE ALSO 2 2 [ 0 0 1 1 ] 0 1 ”Pw
Page 87 and 88: parameterlist is a list of token-ar
Page 89 and 90: Requests a sphere defined by the fo
Page 91 and 92: Hyperboloid 0 0 0 .5 0 0 270 ”Cs
Page 93 and 94: z N z V point2 height U x x y 0 max
Page 95 and 96: particle. If a primitive variable i
Page 97 and 98: The code array is a sequence of mac
Page 99 and 100: is an array of floats that define t
Page 101 and 102: The helper program generates geomet
Page 103 and 104: Procedural ”DynamicLoad” [ ”m
Page 105 and 106: SolidBegin ( ”difference” ); So
Page 107 and 108: Section 6 MOTION Some rendering pro
Page 109 and 110: Transformations Geometry Shading Ri
Page 111 and 112: channels (usually an RGB color) can
Page 113 and 114: Image Forward Axis Up Axis Right Ax
Page 115 and 116: ErrorHandler ”ignore” ErrorHand
Page 117 and 118: Part II The RenderMan Shading Langu
Page 119 and 120: spaces (such as CMYK or pseudocolor
Page 121: transmit reflect transmit P E light
Page 125 and 126: Section 11 TYPES The Shading Langua
Page 127 and 128: Coordinate System ”shader” ”c
Page 129 and 130: As in C, individual array elements
Page 131 and 132: Light Source E Vantage Point N L Il
Page 133 and 134: Surface Element to Illuminate L N I
Page 135 and 136: Name Type Storage Class Description
Page 137 and 138: • conditional execution, • loop
Page 139 and 140: This example integrates over a hemi
Page 141 and 142: Shader instance variable values can
Page 143 and 144: } return 2 * (vector noise(p)) - 1;
Page 145 and 146: These functions compute power and i
Page 147 and 148: The actual change in a variable is
Page 149 and 150: Return a unit vector in the directi
Page 151 and 152: Return surface normal given a point
Page 153 and 154: diffuse returns the diffuse compone
Page 155 and 156: prevent aliasing. If one set of tex
Page 157 and 158: 15.7.3 Shadow depth maps Shadow dep
Page 159 and 160: These functions access the value of
Page 161 and 162: The standard data names supported b
Page 163 and 164: } Oi = sum; Ci = Cs * Oi * (Ka + Kd
Page 165 and 166: path of the ray. The input Ci and O
Page 167 and 168: A.2.3 Metal surface surface metal(
Page 169 and 170: distantlight( float intensity = 1;
Page 171 and 172: A.6 Imager Shaders A.6.1 Background
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variable definitions ; variables va
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triple sixteentuple arrayindex: [ e
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Logical expressions have the value
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typedef RtPointer RtContextHandle;
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RiOptionV(RtToken name, RtInt n, Rt
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RtInt n, RtToken tokens[], RtPointe
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#define RIE_NOTATTRIBS ((RtInt)26)
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Comments Any occurrence of the ’#
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In the following sections the synta
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C.2.2 Error handling There are two
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adhandle badparamlist badripcode ba
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v e r s i o n 212 # version 003 007
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Using RIB File structuring conventi
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Attribute Format PixelFilter Shadin
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##Include filename This entry allow
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D.2.1 RIB Entity File example ##Ren
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Motion Blur Programmable Shading Di
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} E.4 Gaussian Filter RtFloat RiGau
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Appendix G RENDERMAN INTERFACE QUIC
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Function RiOpacity (color) RiOption
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Geometric Primitives (continued) Fu
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Function abs(x) Math Functions Desc
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Function area(P) calculatenormal(P)
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Texture Mapping Functions Function
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RiInterior 47 RiLightSource 42 RiMa
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and uniform variables on an RiNuPat
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Statement About Pixar’s Copyright
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The RenderMan Interface - Paul Bourke

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