The RenderMan Interface - Paul Bourke

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Section 15 BUILT-IN FUNCTIONS The following built-in functions are provided in the Shading Language. 15.1 Mathematical Functions The following library of math functions is provided. This library includes most of the routines normally found in the standard C math library as well as functions for interpolation and computing derivatives. The following mathematical functions are provided: float PI = 3.14159... ; float radians ( float degrees ) float degrees ( float radians ) float sin ( float a ) float asin ( float a ) float cos ( float a ) float acos ( float a ) float tan ( float a ) float atan ( float yoverx ), atan( float y, x ) The predefined float constant PI is the value of π. The function radians converts from degrees to radians; and conversely, the function degrees converts from radians to degrees. sin, cos, and tan are the standard trigonometric functions of radian arguments. asin returns the arc sine in the range −π/2 to π/2. acos returns the arc cosine in the range 0 to π. atan with one argument returns the arc tangent in the range −π/2 to π/2. atan with two arguments returns the arc tangent of y/x in the range −π to π. float pow( float x, y ) float exp( float x ) float sqrt( float x ) float inversesqrt( float x ) float log( float x ), log( float x, base ) 133
These functions compute power and inverse power functions. pow returns x y , exp returns e x . sqrt returns the positive square root of x, and inversesqrt(x) returns 1/sqrt(x). log with one argument returns the natural logarithm of x (x = log(exp(x))). log with two arguments returns the logarithm in the specified base (x = log(pow(base, x), base)). float mod ( float a, b ) float abs ( float x ) float sign ( float x ) mod returns a value greater than 0 and less than or equal to b such that mod(a,b) = a - n*b for some integer n. abs returns the absolute value of its argument and sign returns -1 if its argument is negative, 1 if its argument is positive, and 0 if its argument is zero. type min (type a, b, ... ) type max ( type a, b, ... ) type clamp ( type a, min, max ) min takes a list of two or more arguments of identical type and returns the argument with minimum value; max returns the argument with maximum value. clamp(a,min,max) returns min if a is less than min, max if a is greater than max; otherwise it returns a. The type may be any of float, point, vector, normal, or color. The variants that operate on colors or point-like objects operate on a component-by-component basis (e.g., separately for x, y, and z). float mix (float x, y; float alpha ) point mix (point x, y; float alpha ) vector mix (vector x, y; float alpha ) normal mix (normal x, y; float alpha ) color mix (color x, y; float alpha ) mix returns x · (1 − α) + y · α, that is, it performs a linear blend between values x and y. The types of x and y must be identical, but may be any of float, point, vector, normal, or color. The variants that operate on colors or point-like objects operate on a component-by-component basis (e.g., separately for x, y, and z). float floor ( float x ) float ceil ( float x ) float round ( float x ) floor returns the largest integer (expressed as a float) not greater than x. ceil returns the smallest integer (expressed as a float) not smaller than x. round returns the integer closest to x. float step ( float min, value ) float smoothstep ( float min, max, value ) 134
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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
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4.3.2 Transformation stack Transfor
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Section 5 GEOMETRIC PRIMITIVES The
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Information Name Type Class Floats
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No checking is done by the RenderMa
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5.2 Patches Patches can be either u
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U V 0 1 2 3 12 13 14 15 4 5 6 7 8 9
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10 x 7 Aperiodic Bezier Bicubic Pat
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SEE ALSO 2 2 [ 0 0 1 1 ] 0 1 ”Pw
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parameterlist is a list of token-ar
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Requests a sphere defined by the fo
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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 and 122: transmit reflect transmit P E light
Page 123 and 124: Section 10 RELATIONSHIP TO THE REND
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: } return 2 * (vector noise(p)) - 1;
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
Page 173 and 174: variable definitions ; variables va
Page 175 and 176: triple sixteentuple arrayindex: [ e
Page 177 and 178: Logical expressions have the value
Page 179 and 180: typedef RtPointer RtContextHandle;
Page 181 and 182: RiOptionV(RtToken name, RtInt n, Rt
Page 183 and 184: RtInt n, RtToken tokens[], RtPointe
Page 185 and 186: #define RIE_NOTATTRIBS ((RtInt)26)
Page 187 and 188: Comments Any occurrence of the ’#
Page 189 and 190: In the following sections the synta
Page 191 and 192: C.2.2 Error handling There are two
Page 193 and 194: 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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