This document discusses using a dynamic color palette system for toon rendering. It describes how a typical workflow uses static color palettes and masks, which has disadvantages like extra disk usage and work when geometry changes. The presented solution uses a node-based network to generate code for a dynamic color palette shader. The shader selects palettes and colors based on conditions like object properties, time, lights. This allows space-time varying palettes with less composition work. Future work could make palettes fully dynamic by mapping colors to textures over a network.

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Space Time Varying
Color Palette
Bo ZHOU
J Cube Inc.
!
Paolo Berto Durrante
J Cube Inc.
Polygon Pictures Inc.

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Introduction

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Toon Rendering
no PBR
flat shading
artistic design

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Color Palette
color matrix
object index
semantics

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Color Palette
column
object index
row
semantics
lit color
shadow color
2nd shadow color
outline color etc.

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Color Palette
Daylight Night Jungle Sunset

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Color Palette
advantage
fast design
reusable
material/shading system independent

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Color Palette
disadvantage
static color
predefined before rendering

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Reality

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Problem
Character was lit by both environment light
and visual effect elements.

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Typical Workflow
create 2 color plattes
1 according environment and 2 for vfx
generate masks from renderer
fill the regions in post composition software
R = Lit, G
= Shadow,
Y =
Specular
Object Id

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Typical Workflow
disadvantage
image was done in composition
software.
extra overhead on disk usage
more masks
not invertible
once geometry was changed, must
regenerate the all masks

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Goal
finish the image in renderer
less disk usage
maximal flexibility as manual switching the
color palette in composition software

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Solution

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Solution
DAG network
a typed eventing network
time
space position
special light
…
generate dynamic code for specific network
independent from any renderer/software
what we want is a set of colors outputed from the network
constant statement will be optimised by compiler

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Use Case
2 palettes, use the 1st between frame 1 - 4
but the rest associated with 2nd

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Use Case
generated shader code
class jcubeToon5_PalettesCoShader_1()
{
uniform float num_rows = 5 ;
uniform float cell_size = 30 ;
uniform float border_size = 2 ;
!public uniform float has_light_event = 0 ;
!uniform string color_palettes[2] =
{
"/Users/Bo/Documents/maya/projects/default/sourceimages/Palette_A.tif" , // file2
"/Users/Bo/Documents/maya/projects/default/sourceimages/Palette_B.tif" // file1
};
!public void construct()
{
Gather( color_palettes[0] , cell_size , border_size , num_rows ) ;
Gather( color_palettes[1] , cell_size , border_size , num_rows ) ;
}
!//////////////////////////////////////////
public void surface( output color Ci , Oi ;
output color outputs[5] ;
uniform float float_index = - 1 ;
color color_index = 0 )
{
float choice = - 1 ;
! // jcubeToonNumericEvent1
//
float jcubeToonNumericEvent1_outputs = - 1 ;
uniform float jcubeToonNumericEvent1_first_term = 1.0 ;
uniform float jcubeToonNumericEvent1_second_term = 4.0 ;
uniform float jcubeToonNumericEvent1_if_palette = 0 ; // file2
uniform float jcubeToonNumericEvent1_else_palette = 1 ; // file1
if ( jcubeToonNumericEvent1_first_term > jcubeToonNumericEvent1_second_term )
{
jcubeToonNumericEvent1_outputs = jcubeToonNumericEvent1_if_palette ;
}
else
{
jcubeToonNumericEvent1_outputs = jcubeToonNumericEvent1_else_palette ;
}
choice = jcubeToonNumericEvent1_outputs ;
if ( float_index > - 1 )
{
Search( color_palettes[choice] , float_index , outputs ) ;
}
else
{
Search( color_palettes[choice] , color_index , outputs ) ;
}
}
}

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Use Case
if (“P” in pCube1)
if (time > 4)
pick A
else
pick C
else
pick B

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Use Case
class jcubeToon5_PalettesCoShader_1()
{
uniform float num_rows = 5 ;
uniform float cell_size = 30 ;
uniform float border_size = 2 ;
!public uniform float has_light_event = 0 ;
!uniform string color_palettes[3] =
{
"/Users/Bo/Documents/maya/projects/default/sourceimages/Palette_C.tif" , // file3
"/Users/Bo/Documents/maya/projects/default/sourceimages/Palette_A.tif" , // file2
"/Users/Bo/Documents/maya/projects/default/sourceimages/Palette_B.tif" // file1
};
!public void construct()
{
Gather( color_palettes[0] , cell_size , border_size , num_rows ) ;
Gather( color_palettes[1] , cell_size , border_size , num_rows ) ;
Gather( color_palettes[2] , cell_size , border_size , num_rows ) ;
}
!float inside_box( uniform point box_min , box_max ; point x )
{
if ( x[0] > box_min[0] && x[0] < box_max[0] )
if ( x[1] > box_min[1] && x[1] < box_max[1] )
if ( x[2] > box_min[2] && x[2] < box_max[2] )
return 1 ;
return 0 ;
}
!float inside_sphere( uniform point sphere_position ; uniform float sphere_radius ; point x )
{
if ( distance( x , sphere_position ) < sphere_radius )
return 1 ;
return 0 ;
}
!float inside_cone( uniform point cone_position ; uniform vector cone_direction ; uniform float cone_angle ; point x )
{
color a = transmission( cone_position , x , "samples" , 1 ) ;
float b = step( cos( radians( cone_angle ) * 0.5 ) , normalize( x - cone_position ) . normalize( cone_direction ) ) ;
return a[0] * b ;
}
!//////////////////////////////////////////
public void surface( output color Ci , Oi ;
output color outputs[5] ;
uniform float float_index = - 1 ;
color color_index = 0 )
{
point Pw = transform( "current" , "world" , P ) ;
!float choice = - 1 ;
!// jcubeToonNumericEvent1
//
float jcubeToonNumericEvent1_outputs = - 1 ;
uniform float jcubeToonNumericEvent1_first_term = 1.0 ;
uniform float jcubeToonNumericEvent1_second_term = 4.0 ;
uniform float jcubeToonNumericEvent1_if_palette = 1 ; // file2
uniform float jcubeToonNumericEvent1_else_palette = 2 ; // file1
if ( jcubeToonNumericEvent1_first_term > jcubeToonNumericEvent1_second_term )
{
jcubeToonNumericEvent1_outputs = jcubeToonNumericEvent1_if_palette ;
}
else
{
jcubeToonNumericEvent1_outputs = jcubeToonNumericEvent1_else_palette ;
}
// jcubeToonRegionEvent2
//
float jcubeToonRegionEvent2_outputs = - 1 ;
point jcubeToonRegionEvent2_Pw = Pw ;
float jcubeToonRegionEvent2_in_palette = jcubeToonNumericEvent1_outputs ; // jcubeToonNumericEvent1
uniform float jcubeToonRegionEvent2_out_palette = 0 ; // file3
uniform point jcubeToonRegionEvent2_box_min = point(-0.14332814514636993, 8.197878287319327e-08, -5.021854877471924) ;
uniform point jcubeToonRegionEvent2_box_max = point(2.2686707973480225, 7.261795997619629, -1.861090064048767) ;
if ( inside_box( jcubeToonRegionEvent2_box_min , jcubeToonRegionEvent2_box_max , jcubeToonRegionEvent2_Pw ) > 0 )
{
jcubeToonRegionEvent2_outputs = jcubeToonRegionEvent2_in_palette ;
}
else
{
jcubeToonRegionEvent2_outputs = jcubeToonRegionEvent2_out_palette ;
}
choice = jcubeToonRegionEvent2_outputs ;
if ( float_index > - 1 )
{
Search( color_palettes[choice] , float_index , outputs ) ;
}
else
{
Search( color_palettes[choice] , color_index , outputs ) ;
}
}
}
Sorry, a bit long then :)

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Renderer
to the RSL-like renderer (3Delight)
generate coshader
invoked by shader as a black box
to the DSO renderer (mental ray)
generate LLVM JIT code
directly executed by shader as part of
the shader

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Conclusion
advantage
reusable network for similar objects
much less composition work
cover all most any situations
space-varying or time-varying

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Future
get rid of color palette completely
web+databased solution
abstract color palette
mapping semantics color to anything
replace color in cell with texture stream over
network
interactive feedback when changing palette

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Thanks !
Q&A