The RenderMan Interface - Paul Bourke

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Coordiante System ”object” ”world” ”camera” ”screen” ”raster” ”NDC” Description The coordinate system in which the current geometric primitive is defined. The modeling transformation converts from object coordinates to world coordinates. The standard reference coordinate system. The camera transformation converts from world coordinates to camera coordinates. A coordinate system with the vantage point at the origin and the direction of view along the positive z-axis. The projection and screen transformation convert from camera coordinates to screen coordinates. The 2-D normalized coordinate system corresponding to the image plane. The raster transformation converts to raster coordinates. The raster or pixel coordinate system. An area of 1 in this coordinate system corresponds to the area of a single pixel. This coordinate system is either inherited from the display or set by selecting the resolution of the image desired. Normalized device coordinates — like ”raster” space, but normalized so that x and y both run from 0 to 1 across the whole (uncropped) image, with (0,0) being at the upper left of the image, and (1,1) being at the lower right (regardless of the actual aspect ratio). Table 4.2: Point Coordinate Systems imaging process was described above. When RiBegin is executed it establishes a complete set of defaults. If the rendering program is designed to produce pictures for a particular piece of hardware, display parameters associated with that piece of hardware are used. If the rendering program is designed to produce picture files, the parameters are set to generate a video-size image. If these are not sufficient, the resolution and pixel aspect ratio can be set to generate a picture for any display device. RiBegin also establishes default screen and camera coordinate systems as well. The default projection is orthographic and the screen coordinates assigned to the display are roughly between ±1.0. The initial camera coordinate system is mapped onto the display such that the +x axis points right, the +y axis points up, and the +z axis points inward, perpendicular to the display surface. Note that this is left-handed. Before any transformation commands are made, the current transformation matrix contains the identity matrix as the screen transformation. Usually the first transformation command is an RiProjection, which appends the projection matrix onto the screen transformation, saves it, and reinitializes the current transformation matrix as the identity camera transformation. This marks the current coordinate system as the camera coordinate system. After the camera coordinate system is established, future transformations move the world coordinate system relative to the camera coordinate system. When an RiWorldBegin is executed, the current transformation matrix is saved as the camera transformation, and thus the world coordinate system is established. Subsequent transformations inside of an RiWorldBegin- RiWorldEnd establish different object coordinate systems. 21
ottom top left right Screen Window Y Image plane (Screen coordinates) X Y Camera Perspective Viewing coordinates Frustum (Pyramid) Screen-to-Raster Z Mapping X Display device (Raster coordinates) X Crop Window Y xresolution * pixel-a.r. frame-a.r. Output image resolution yresolution Display maximum resolution xresolution Figure 4.1: Camera-to-Raster Projection Geometry The following example shows how to position a camera: RiBegin (); RiFormat ( xres, yres, 1.0 ); /* Raster coordinate system */ RiFrameAspectRatio ( 4.0/3.0 ); /* Screen coordinate system */ RiFrameBegin (0); RiProjection (”perspective,”...); /* Camera coordinate system */ RiRotate (... ); RiWorldBegin (); /* World coordinate system */ ... RiTransform (...); /* Object coordinate system */ RiWorldEnd (); RiFrameEnd (); RiEnd (); The various camera procedures are described below, with some of the concepts illustrated in Figure 4.1, Camera-to-Raster Projection Geometry. 22
Page 1 and 2: The RenderMan Interface Version 3.2
Page 3 and 4: TABLE OF CONTENTS List of Figures L
Page 5 and 6: 12.1 Surface Shaders . . . . . . .
Page 7 and 8: Section I DIFFERENCES BETWEEN VERSI
Page 9 and 10: LIST OF TABLES 4.1 Camera Options .
Page 11 and 12: PREFACE This document is version 3.
Page 13 and 14: Section 1 INTRODUCTION The RenderMa
Page 15 and 16: created using this language. This l
Page 17 and 18: Depth of Field The ability to simul
Page 19 and 20: typedef RtPointer typedef RtPointer
Page 21 and 22: RiContext (ctx1); ... There is no R
Page 23 and 24: Section 3 RELATIONSHIP TO THE RENDE
Page 25 and 26: through the interface. Any place wh
Page 27 and 28: RtContextHandle RiGetContext ( void
Page 29 and 30: RiWorldBegin (); ... RiColor (...);
Page 31: Camera Option Type Default Descript
Page 35 and 36: EXAMPLE RiFrameAspectRatio (4.0/3.0
Page 37 and 38: not support the special projection
Page 39 and 40: This procedure sets the times at wh
Page 41 and 42: Output depth values are the camera-
Page 43 and 44: A particular renderer implementatio
Page 45 and 46: Renderers may additionally produce
Page 47 and 48: The number of color components, n,
Page 49 and 50: RiAttributeBegin () RiAttributeEnd
Page 51 and 52: RIB BINDING Color c0 c1... cn Color
Page 53 and 54: An area light source is defined by
Page 55 and 56: The sequencenumber is the integer l
Page 57 and 58: 4.2.5 Displacement shading The grap
Page 59 and 60: SEE ALSO RiExterior RiAtmosphere Ri
Page 61 and 62: Matte onoff EXAMPLE RiMatte (RI TRU
Page 63 and 64: object foo2 will be drawn when the
Page 65 and 66: the exterior is the region adjacent
Page 67 and 68: RiIdentity ( ); SEE ALSO RiTransfor
Page 69 and 70: 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
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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
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z N z V point2 height U x x y 0 max
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particle. If a primitive variable i
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The code array is a sequence of mac
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is an array of floats that define t
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The helper program generates geomet
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Procedural ”DynamicLoad” [ ”m
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SolidBegin ( ”difference” ); So
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Section 6 MOTION Some rendering pro
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Transformations Geometry Shading Ri
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channels (usually an RGB color) can
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Image Forward Axis Up Axis Right Ax
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ErrorHandler ”ignore” ErrorHand
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Part II The RenderMan Shading Langu
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spaces (such as CMYK or pseudocolor
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transmit reflect transmit P E light
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Section 10 RELATIONSHIP TO THE REND
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Section 11 TYPES The Shading Langua
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Coordinate System ”shader” ”c
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As in C, individual array elements
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Light Source E Vantage Point N L Il
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Surface Element to Illuminate L N I
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Name Type Storage Class Description
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• conditional execution, • loop
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This example integrates over a hemi
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Shader instance variable values can
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} return 2 * (vector noise(p)) - 1;
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These functions compute power and i
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The actual change in a variable is
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Return a unit vector in the directi
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Return surface normal given a point
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diffuse returns the diffuse compone
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prevent aliasing. If one set of tex
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15.7.3 Shadow depth maps Shadow dep
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These functions access the value of
Page 161 and 162:
The standard data names supported b
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} Oi = sum; Ci = Cs * Oi * (Ka + Kd
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path of the ray. The input Ci and O
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A.2.3 Metal surface surface metal(
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distantlight( float intensity = 1;
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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
Page 225 and 226:
Statement About Pixar’s Copyright
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The RenderMan Interface - Paul Bourke

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