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1.1 |
RADIANCE Scene Description Language
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Altogether there are at least 4 "languages" involved with Radiance
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scene descriptions: the basic scene input language, the function file
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language, the data file language and the font language.
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Scene Input
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===========
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scenefile: /* nothing */
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| statement scenefile
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statement: primitive
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| alias
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| command
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| comment
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primitive: modifier type STRING
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INTEGER string_args
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INTEGER integer_args
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INTEGER real_args
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alias: modifier alias STRING STRING
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modifier: "void"
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| "inherit"
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| STRING
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command: '!' STRING string_args command_end
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command_end: '\n'
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| '\\' '\n' string_args command_end
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comment: '#' string_args '\n'
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string_args: /* nothing */
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| STRING string_args
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integer_args: /* nothing */
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| INTEGER integer_args
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real_args: /* nothing */
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| REAL real_args
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type: "polygon"
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| "cone"
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| "sphere"
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| "texfunc"
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| "ring"
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| "cylinder"
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| "instance"
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| "cup"
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| "bubble"
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| "tube"
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| "mesh"
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| "plastic"
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| "metal"
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| "glass"
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| "trans"
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| "dielectric"
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| "plastic2"
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| "metal2"
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| "trans2"
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| "interface"
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| "plasfunc"
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| "metfunc"
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| "brightfunc"
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| "brightdata"
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| "brighttext"
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| "colorpict"
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| "glow"
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| "source"
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| "light"
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| "illum"
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| "spotlight"
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| "mist"
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| "mirror"
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| "transfunc"
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| "BRTDfunc"
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| "plasdata"
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| "metdata"
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| "transdata"
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| "colorfunc"
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| "antimatter"
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| "colordata"
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| "colortext"
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| "texdata"
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| "mixfunc"
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| "mixdata"
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| "mixtext"
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| "prism1"
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| "prism2"
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Function File
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=============
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funcfile: /* nothing */
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| decl funcfile
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decl: ';'
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| function_decl ';'
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| variable_decl ';'
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function_decl: ID '(' id_list ')' assign_op e1
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variable_decl: ID assign_op e1
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id_list: ID
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| ID ',' id_list
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assign_op: '='
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| ':'
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e1: e1 '+' e2
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| e1 '-' e2
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| e2
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e2: e2 '*' e3
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| e2 '/' e3
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| e3
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e3: e4 '^' e3
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| e4
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e4: '+' e5
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| '-' e5
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| e5
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e5: '(' e1 ')'
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| ID
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| ID '(' id_list ')'
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| REAL
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| '$' INTEGER
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Comments may appear between any two tokens set off by curly braces {},
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and may be nested to any level.
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Data File
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=========
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data: dimensions value_list
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dimensions: INTEGER dim_list
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dim_list: dim
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| dim dim_list
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dim: REAL REAL INTEGER
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| '0' '0' INTEGER indep_list
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indep_list: REAL
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| REAL indep_list
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value_list: /* nothing */
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| REAL value_list
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Comments begin with a pound sign ('#') and continue to the end of line.
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Font File
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=========
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glyph_list: /* nothing */
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| glyph glyph_list
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glyph: INTEGER INTEGER coord_list
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coord_list: /* nothing */
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| INTEGER INTEGER coord_list
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Comments begin with a pound sign ('#') and continue to the end of line.
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--------------------------------------------------------------
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With regards to your topics, I have the following comments.
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Specification of scene parameters:
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- Radiance uses a right-hand coordinate system
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- The eyepoint and view direction are given as options
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to the renderers, and can be stored in a separate file
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Supported primitives:
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- N-sided polygons
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- spheres
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- cones, cylinders, rings
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- hierarchical instancing for very complex geometries
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Lighting models:
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- Completely general
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- Converter provided for IES luminaire specification
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Participating media:
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- Single-scatter approximation
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- Mist zones may have different scattering/absorption properties
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Textures:
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- I break "textures" into two kinds, patterns and textures
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- Patterns are variation in color, and can be specified as
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pictures, data or functions in any combination
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- Textures are perturbations in surface normal, and can
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be specified in the same ways as patterns
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- A light source distribution is a pattern
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Bit Mapping:
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- Usually given as a picture-type pattern (ie. "colorpict" type)
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- True bit-maps (ie. 1-bit depth images) may also be produced
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using a special bit font
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CSG:
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- Radiance has an "antimatter" type which supports some rudimentary
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CSG subtraction, but otherwise we are strictly B-rep
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Looping constructs or Recursion:
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- The function file language supports recursion
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- The "xform" program provides iteration for repeated objects
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Functions or Procedures:
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- The function file language supports functions without side effects
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User extensibility:
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- The user may create function files, data files and font files,
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or provide his/her own images for patterns
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- General bidirectional reflection distribution functions may
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also be specified in the same way as patterns and textures
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