RenderMan Tutorial

1
RenderMan Tutorial

• COMP238 Fall 2000

2
Overview

• Two languages
• Geometry - set of C subroutines
• Shading - a C-like language
• Geometry code can be run directly, or output to
  RIB file
• Shading code is compiled to byte-code

3
Process
RIB File
Rman Geom Code
Rman Program
cc
render Program
Rman Shader .sl
shader
Byte-code Shader .slo
Image File
txmake
TIFF image
Rman texture
4
Local Configuration

• Files are in /usr/local/prman
• On Suns, SGI, Linux
• File /usr/local/prman/rendermn.ini has default
  values (file paths, etc).
• You can make your own .rendermn.ini to override
• Blue Moon now does Windows

5
Resources

• RenderMan Companion copies in Glab
• Pixar web pages
• http//www.pixar.com/products/renderman/toolkit/To
  olkit/user.html
• Look on course resources web page for links

6
RenderMan code

• include ltri.hgt
• RtPoint Square4 .5,.5,.5, .5,-.5,.5,
  -.5,-.5,.5, -.5,.5,.5
• main(void)
• RiBegin(RI_NULL) / Start the renderer /
• RiDisplay("RenderMan", RI_FRAMEBUFFER,
  "rgb", RI_NULL)
• RiFormat((RtInt) 256, (RtInt) 192, -1.0)
• RiShadingRate(1.0)
• RiWorldBegin()
• RiSurface("constant", RI_NULL)
• RiPolygon( (RtInt) 4, /
  Declare the square /
• RI_P, (RtPointer) Square,
  RI_NULL)
• RiWorldEnd()
• RiEnd() / Clean up /

7
RIB

• Display "RenderMan" "framebuffer" "rgb"
• Format 256 192 -1
• ShadingRate 1
• WorldBegin
• Surface "constant"
• Polygon "P" 0.5 0.5 0.5 0.5 -0.5 0.5 -0.5 -0.5
  0.5 -0.5 0.5 0.5
• WorldEnd

8
Output to a File

• Examples have display output
• RiDisplay("RenderMan", RI_FRAMEBUFFER, "rgb",
  RI_NULL)
• Change to
• RiDisplay("filename", RI_FILE, RI_RGBA,
  RI_NULL)
• or RIB to
• Display "filename" "file" "rgba"

9
Making a Model

• Procedural
• RIB files on web
• Look at my resources page
• Many programs output RIB
• Format converter

10
Parameter Lists

• Variable length
• Name/Value pairs or vector
• RiPatch(RI_BICUBIC, RI_P, (RtPointer)
• Patch, RI_NULL)

11
Surface Shader Specification

• ks 0.5 ka kd 0
• RiSurface("plastic",
• (RtToken)"Ka", (RtPointer)ka,
• (RtToken)"Kd", (RtPointer)kd,
• (RtToken)"Ks", (RtPointer)ks,
• RI_NULL)
• RiCylinder(0.5, -0.5, 0.5, 360.0, RI_NULL)

12
Shader Instances

• ks 0.5 ka kd 0
• RiSurface("plastic",
• (RtToken)"Ka", (RtPointer)ka,
• (RtToken)"Kd", (RtPointer)kd,
• (RtToken)"Ks", (RtPointer)ks,
• RI_NULL)
• RiCylinder(0.5, -0.5, 0.5, 360.0, RI_NULL)
• ks 0.2 ka 0.3 kd 0.1
• RiSurface("plastic",
• (RtToken)"Ka", (RtPointer)ka,
• (RtToken)"Kd", (RtPointer)kd,
• (RtToken)"Ks", (RtPointer)ks,
• RI_NULL)

13
Shader Example

• surface clouds(float Kd.8, Ka.2 )
• float sum
• float i, freq
• color white color(1.0, 1.0, 1.0)
• point Psh transform("shader", P)
• sum 0
• freq 4.0
• for (i 0 i lt 6 i i 1)
• sum sum 1/freq abs(.5 - noise(freq
  Psh))
• freq 2 freq
• Ci mix(Cs, white, sum4.0)
• Oi 1.0 / Always make the
  surface opaque /

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Result
15
Shader Example (defaults)
Must have default values

• surface clouds(float Kd.8, Ka.2 )
• float sum
• float i, freq
• color white color(1.0, 1.0, 1.0)
• point Psh transform("shader", P)
• sum 0
• freq 4.0
• for (i 0 i lt 6 i i 1)
• sum sum 1/freq abs(.5 - noise(freq
  Psh))
• freq 2 freq
• Ci mix(Cs, white, sum4.0)
• Oi 1.0 / Always make the
  surface opaque /

16
Why?

• Because youre not required to specify
  parameters
• RiWorldBegin()
• RiColor(color)
• RiSurface("clouds", RI_NULL)
• RiPolygon( (RtInt) 4,
• RI_P, (RtPointer) Square, RI_NULL)
• RiWorldEnd()

17
Shader Example (data types)

• surface clouds(float Kd.8, Ka.2 )
• float sum
• float i, freq
• color white color(1.0, 1.0, 1.0)
• point Psh transform("shader", P)
• sum 0
• freq 4.0
• for (i 0 i lt 6 i i 1)
• sum sum 1/freq abs(.5 - noise(freq
  Psh))
• freq 2 freq
• Ci mix(Cs, white, sum4.0)
• Oi 1.0 / Always make the
  surface opaque /

Specialized data types
18
Data Types

• Float (no integer!)
• String
• Point
• Color
• New in latest RenderMan
• Vector, matrix
• Also arrays of any type

19
Uniform vs. Varying

• Uniform means that the parameter is the same
  across surface
• More efficient
• default
• Varying variables can be attached to vertices
• Interpolated across surface

20
Shader (magic variables)

• surface clouds(float Kd.8, Ka.2 )
• float sum
• float i, freq
• color white color(1.0, 1.0, 1.0)
• point Psh transform("shader", P)
• sum 0
• freq 4.0
• for (i 0 i lt 6 i i 1)
• sum sum 1/freq abs(.5 - noise(freq
  Psh))
• freq 2 freq
• Ci mix(Cs, white, sum4.0)
• Oi 1.0 / Always make the
  surface opaque /

Surface position
Color and opacity
21
Predefined Global Variables

• Position P
• Normal N
• Surface color Cs
• Output color Ci
• Output opacity Oi
• Others P.292 of RenderMan Companion

22
Shader (built-in functions)

• surface clouds(float Kd.8, Ka.2 )
• float sum
• float i, freq
• color white color(1.0, 1.0, 1.0)
• point Psh transform("shader", P)
• sum 0
• freq 4.0
• for (i 0 i lt 6 i i 1)
• sum sum 1/freq abs(.5 - noise(freq
  Psh))
• freq 2 freq
• Ci mix(Cs, white, sum4.0)
• Oi 1.0 / Always make the
  surface opaque /

23
Built-in Functions

• Trig functions
• Standard math
• Texture, bump, environment, and shadow mapping
  functions
• Geometric - area(), normalize(V)
• printf()

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Shader (return value Ci, Oi)

• surface clouds(float Kd.8, Ka.2 )
• float sum
• float i, freq
• color white color(1.0, 1.0, 1.0)
• point Psh transform("shader", P)
• sum 0
• freq 4.0
• for (i 0 i lt 6 i i 1)
• sum sum 1/freq abs(.5 - noise(freq
  Psh))
• freq 2 freq
• Ci mix(Cs, white, sum4.0)
• Oi 1.0 / Always make the
  surface opaque /

25
Constant Shader

• surface
• constant()
• Oi Os
• Ci Os Cs

26
Lighting

• illuminance(point , axis, angle)
• Executes each light within specified angle
• Rarely used.
• Returns Cl, L

27
Alternate Approach

• Usually shortcut with ambient(), diffuse(),
  specular()
• Examples next

28
Diffuse Surface

• surface
• matte( float Ka 1,
• Kd 1 )
• normal Nf faceforward(normalize(N),I)
• Oi Os
• Ci Os Cs (Kaambient() Kddiffuse(Nf))

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Plastic

• surface plastic( float Ks .5, Kd .5,
• Ka 1, roughness .1
• color specularcolor 1 )
• normal Nf faceforward(normalize(N), I )
• vector V normalize(-I)
• Oi Os
• Ci Os( Cs (Kaambient() Zddiffuse(Nf))
• specularcolor Ks specular(Nf,V,roughness)
  )

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Lights

• The light shaders generate Cl, the intensity of
  the light
• Also control cone of light

31
Ambient Light

• light
• ambientlight(
• float intensity 1
• color lightcolor 1 )
• Cl intensity lightcolor

32
Point Light

• light
• pointlight(
• float intensity 1
• color lightcolor 1
• point from point "camera" (0,0,0) )
• illuminate( from )
• Cl intensity lightcolor / L.L

33
illuminate

• illuminate(position , axis, angle)
• Position specifies apex of cone
• Axis direction of center of cone
• Angle of cone

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What Next?

• Look at Chapter 16 of RenderMan Companion
• Compile and modify some of the examples
• http//www.pixar.com/products/rendermandocs/toolki
  t/Toolkit/tut.html
• will help you with compilation, etc.

35
Other Resources

• RenderMan Docs (PDF and HTML)
• http//www.pixar.com/products/renderman/toolkit/To
  olkit/
• Articles
• http//www.cgrg.ohio-state.edu/smay/RManNotes/
• http//howto.tucows.com/LDP/LDP/LG/issue15/bmrt-pa
  rt1.html
• http//howto.tucows.com/LDP/LDP/LG/issue17/bmrt-pa
  rt2.html