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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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|
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scenefile: /* nothing */ |
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| statement scenefile |
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|
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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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|
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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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|
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alias: modifier alias STRING STRING |
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|
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modifier: "void" |
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| "inherit" |
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| STRING |
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|
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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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|
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comment: '#' string_args '\n' |
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|
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string_args: /* nothing */ |
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| STRING string_args |
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|
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integer_args: /* nothing */ |
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| INTEGER integer_args |
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|
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real_args: /* nothing */ |
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| REAL real_args |
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|
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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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|
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Function File |
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============= |
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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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|
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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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-------------------------------------------------------------- |
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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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|
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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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|
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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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|
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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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