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.\" RCSid $Id$ |
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.EQ |
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delim @@ |
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.EN |
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\f[I]definitions\f[R]. |
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Once a function or variable has been defined, it may be used in later |
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definitions, along with predefined functions such as \f[C]sin(x)\f[R] |
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and \f[C]cos(x)\f[R] and constants such as PI \**. |
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and \f[C]cos(x)\f[R] and constants such as \f[C]PI\f[R]\**. |
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.FS |
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TBD - There once was a footnote here |
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.FE |
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.RE |
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.LP |
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The following are sometimes defined, depending on the program: |
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.IP "\f[B]PI\f[R]" 3 |
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.IP "\f[B]\f[CB]PI\f[B]\f[R]" 3 |
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The ratio of a circle\[cq]s circumference to its diameter. |
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.RS 3 |
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.RE |
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surface normal |
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.RS 3 |
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.RE |
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.LP |
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\f[C]Px, Py, Pz\f[R] :intersection point |
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.IP "\f[B]\f[CB]Px, Py, Pz\f[B]\f[R]" 3 |
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intersection point |
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.RS 3 |
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.RE |
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.IP "\f[B]\f[CB]T\f[B]\f[R]" 3 |
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distance from start |
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.RS 3 |
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.LP |
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Similar to data files, font files are usually read and stored in a |
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lookup table. |
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The data structures for fonts are in src/common/font.h, and the routines |
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for reading and spacing them are in \f[C]src/common/font.c\f[R]. |
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The data structures for fonts are in \f[C]src/common/font.h\f[R], and |
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the routines for reading and spacing them are in |
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\f[C]src/common/font.c\f[R]. |
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The main structure type is \f[C]FONT\f[R]. |
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The routine \f[C]getfont(fname)\f[R] loads a font file from the |
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\f[I]Radiance\f[R] library (set by the \f[C]RAYPATH\f[R] environment |
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\f[I]Radiance\f[R] scene description, some of the same library routines |
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are called indirectly. |
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The header file \f[C]src/common/octree.h\f[R] is needed in addition to |
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the \f[C]src/common/object.\f[R]h file. |
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the \f[C]src/common/object.h\f[R] file. |
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The module \f[C]src/ot/writeoct.c\f[R] contains the main routines for |
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writing an octree to stdout, while \f[C]src/common/readoct.c\f[R] |
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contains the corresponding routines for reading an octree from a file. |
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differ from standard computer graphics images inasmuch as they contain |
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real physical data, namely radiance values at each pixel. |
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To do this, it is necessary to maintain floating point information, and |
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we use a 4-byte/pixel encoding described in Chapter II.5 of Graphics |
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Gems II [Arvo91,p.80]. |
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we use a 4-byte/pixel encoding described in Chapter II.5 of |
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\f[I]Graphics Gems II\f[R] [Arvo91,p.80]. |
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The basic idea is to store a 1-byte mantissa for each of three |
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primaries, and a common 1-byte exponent. |
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The accuracy of these values will be on the order of 1% (±1 in 200) over |
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.IP "\f[B]\f[CB]FORMAT\f[B]\f[R]" 3 |
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A line indicating the file\[cq]s format. |
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At most one \f[C]FORMAT\f[R] line is allowed, and it must be assigned a |
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value of either \f[C]32- bit_rle_rgbe\f[R] or \f[C]32-bit_rle_xyze\f[R] |
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value of either \f[C]32-bit_rle_rgbe\f[R] or \f[C]32-bit_rle_xyze\f[R] |
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to be a valid \f[I]Radiance\f[R] picture. |
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.RS 3 |
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.RE |
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or override old ones. |
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.RS 3 |
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.RE |
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.LP |
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\f[C]PRIMARIES\f[R] The CIE (x,y) chromaticity coordinates of the three |
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(RGB) primaries and the white point used to standardize the |
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picture\[cq]s color system. |
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.IP "\f[B]\f[CB]PRIMARIES\f[B]\f[R]" 3 |
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The CIE (x,y) chromaticity coordinates of the three (RGB) primaries and |
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the white point used to standardize the picture\[cq]s color system. |
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This is used mainly by the \f[B]ra_xyze\f[R] program to convert between |
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color systems. |
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If no \f[C]PRIMARIES\f[R] line appears, we assume the standard primaries |
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defined in \f[C]src/common/color.h\f[R], namely |
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\f[C]0.640 0.330 0.290 0.600 0.150 0.060 0.333 0.333\f[R] for red, |
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green, blue and white, respectively. |
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.PP |
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.RS 3 |
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.RE |
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.LP |
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As always, the end of the header is indicated by an empty line. |
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.SH 4 |
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Resolution String |
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.IP "\f[B]New run-length encoded\f[R]" 3 |
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In this format, the four scanline components (three primaries and |
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exponent) are separated for better compression using adaptive run-length |
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encoding (described by Glassner in Chapter II.8 of Graphics Gems II |
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[Arvo91,p.89]). |
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encoding (described by Glassner in Chapter II.8 of \f[I]Graphics Gems |
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II\f[R] [Arvo91,p.89]). |
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The record begins with an unnormalized pixel having two bytes equal to |
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2, followed by the upper byte and the lower byte of the scanline length |
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(which must be less than 32768). |
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\f[C]luminance(col)\f[R]. |
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.PP |
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If the \f[C]FORMAT\f[R] string indicates XYZ data, then the units of the |
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Y primary are already lm/st/m\*{2\*}, so the above conversion is |
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Y primary are already lm/sr/m\*{2\*}, so the above conversion is |
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unnecessary. |
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.SH 3 |
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\f[BI]Radiance\f[B] programs |
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Here are the relevant calls for reading and copying information headers: |
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.IP "\f[B]\f[CB]int checkheader(FILE *fin, char *fmt, FILE *fout);\f[B]\f[R]" 3 |
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Read the header information from \f[C]fin\f[R], copying to |
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\f[C]fou\f[R]t (unless fout is \f[C]NULL\f[R]), checking any |
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\f[C]fout\f[R] (unless fout is \f[C]NULL\f[R]), checking any |
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\f[C]FORMAT\f[R] line against the string \f[C]fmt\f[R]. |
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The \f[C]FORMAT\f[R] line (if it exists) will not be copied to |
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\f[C]fout\f[R]. |
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Macro** | puts real exposure value \f[C]ex\f[R] to stream \f[C]fp\f[R]. |
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.RS 3 |
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.RE |
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.LP |
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\f[C]iscolcor(s)\f[R] :Macro returns non-zero if the line \f[C]s\f[R] is |
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a \f[C]COLORCORR\f[R] setting. |
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.IP "\f[B]\f[CB]iscolcor(s)\f[B]\f[R]" 3 |
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Macro returns non-zero if the line \f[C]s\f[R] is a \f[C]COLORCORR\f[R] |
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setting. |
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.RS 3 |
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.RE |
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.IP "\f[B]\f[CB]colcorval(cc,s)\f[B]\f[R]" 3 |
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Macro assign color correction value from line \f[C]s\f[R] in the |
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\f[C]COLOR\f[R] variable \f[C]cc\f[R]. |
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.RS 3 |
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.RE |
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.IP "\f[B]\f[CB]scanlen(rs)\f[B]\f[R]" 3 |
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Macro to get the scanline length from the \f[C]RESOL\f[R]U structure |
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Macro to get the scanline length from the \f[C]RESOLU\f[R] structure |
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pointed to by \f[C]rs\f[R]. |
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.RS 3 |
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.RE |
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.RS 3 |
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.RE |
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.IP "\f[B]\f[CB]fscnresolu(slp,nsp,fp)\f[B]\f[R]" 3 |
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Macro to read in a resolution string from \f[C]f\f[R]p and assign the |
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Macro to read in a resolution string from \f[C]fp\f[R] and assign the |
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scanline length and number of scanlines to the integers pointed to by |
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\f[C]slp\f[R] and \f[C]nsp\f[R], respectively. |
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This call expects standard English-text ordered scanlines, and returns |
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access routines in \f[C]src/common/portio.c\f[R] for reading and writing |
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portable binary data. |
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The information header is handled by the routines in |
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s\f[C]rc/common/header.c\f[R], similar to the method described for |
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\f[C]src/common/header.c\f[R], similar to the method described for |
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\f[I]Radiance\f[R] picture files. |
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Here are the main calls from \f[C]src/rt/ambio.c\f[R]: |
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.IP "\f[B]\f[CB]putambmagic(FILE *fp);\f[B]\f[R]" 3 |
