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Revision 1.39 by greg, Mon Dec 9 19:21:38 2024 UTC vs.
Revision 1.40 by greg, Fri Dec 13 18:17:17 2024 UTC

# Line 148 | Line 148 | It is stored as ASCII  text,  with  the  following bas
148           ...
149   </pre>
150  
151 + <p>
152 +
153   A comment line begins with a pound sign, `#'.
154  
155   <p>
# Line 394 | Line 396 | The basic types are given below.
396          0
397   </pre>
398  
399 + <p>
400          If the modifier is &quot;void&quot;, then surfaces will
401          use the modifiers  given  in  the  original  description.  
402          Otherwise, the modifier specified is used in their  place.  
# Line 438 | Line 441 | The basic types are given below.
441          0
442   </pre>
443  
444 + <p>
445 +
446          If the modifier is &quot;void&quot;, then surfaces will
447          use the modifiers  given  in  the  original  mesh description.  
448          Otherwise, the modifier specified is used in their  place.  
# Line 532 | Line 537 | A material defines the way light interacts with a  sur
537          4 red green blue maxrad
538   </pre>
539  
540 + <p>
541          If maxrad is zero, then the surface will never be tested for shadow,  although  it  may participate in an interreflection calculation.  
542          If maxrad is negative, then the  surface  will never  contribute  to scene illumination.  
543          Glow sources will never illuminate objects on the other side of an illum  surface.  
# Line 603 | Line 609 | This is only appropriate if the surface hides other (m
609          n A1 A2 .. An
610   </pre>
611  
612 + <p>
613 +
614          The new direction variables dx, dy and dz need not produce a normalized  vector.  
615          For convenience, the variables DxA, DyA and DzA are defined as the normalized direction to the  target  light  source.  
616          See <a HREF="#Function">section 2.2.1</a> on function files for further information.
# Line 646 | Line 654 | This is only appropriate if the surface hides other (m
654          3  source1  mirror1&gt;source10  mirror2&gt;mirror1&gt;source3
655   </pre>
656  
657 + <p>
658   Normally, only one source is given per mist material, and there is an
659   upper limit of 32 to the total number of active scattering sources.
660   The extinction coefficient, if given, is added the the global
# Line 666 | Line 675 | forward direction, as fit by the Henyey-Greenstein fun
675          P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5
676   </pre>
677  
678 + <p>
679 +
680   A perfectly isotropic scattering medium has a g parameter of 0, and
681   a highly directional material has a g parameter close to 1.
682   Fits to the g parameter may be found along with typical extinction
# Line 680 | Line 691 | cloud types in USGS meteorological tables.
691          0|3|6|7 [ rext gext bext [ ralb galb balb [ g ] ] ]
692   </pre>
693  
694 + <p>
695 +
696   There are two usual uses of the mist type.
697   One is to surround a beam from a spotlight or laser so that it is
698   visible during rendering.
# Line 857 | Line 870 | unless the line integrals consider enclosed geometry.
870              A10 ..
871   </pre>
872  
873 + <p>
874 +
875   The sum of specular reflectance (<I>rs</I>), specular transmittance (<I>ts</I>),
876   diffuse reflectance (<I>rfdif gfdif bfdif</I> for front and <I>rbdif gbdif bbdif</I> for back)
877   and diffuse transmittance (<I>rtdif gtdif btdif</I>) should be less than 1 for each
# Line 950 | Line 965 | well-defined, so that all components are fully compute
965          tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn
966   </pre>
967  
968 + <p>
969 +
970          Standard 88% transmittance glass  has  a  transmissivity  of 0.96.  
971          (A <a HREF="#Patterns">pattern</a> modifying glass will affect the transmissivity.)
972          If a fourth real argument is given,  it  is  interpreted as the index of refraction to use instead of 1.52.
# Line 981 | Line 998 | well-defined, so that all components are fully compute
998          4+ red green blue spec A5 ..
999   </pre>
1000  
1001 + <p>
1002 +
1003          The function refl takes four arguments, the x, y and z
1004          direction towards the incident light, and the solid angle
1005          subtended by the source.
# Line 1022 | Line 1041 | well-defined, so that all components are fully compute
1041          6+ red green blue rspec trans tspec A7 ..
1042   </pre>
1043  
1044 + <p>
1045 +
1046          Where trans is the total light transmitted and tspec is  the non-Lambertian  fraction of transmitted light.  
1047          The function brtd should integrate to 1 over each projected hemisphere.
1048  
# Line 1049 | Line 1070 | well-defined, so that all components are fully compute
1070               A10 ..
1071   </pre>
1072  
1073 + <p>
1074 +
1075          The variables rrefl, grefl and brefl specify the color coefficients  for  the ideal specular (mirror) reflection of the surface.  
1076          The variables rtrns, gtrns and btrns  specify  the color coefficients for the ideal specular transmission.  
1077          The functions rbrtd, gbrtd and bbrtd take the direction to the incident light (and its solid angle) and  
# Line 1093 | Line 1116 | well-defined, so that all components are fully compute
1116          4+ red green blue spec A5 ..
1117   </pre>
1118  
1119 + <p>
1120 +
1121          The coordinate indices (x1, x2, etc.) are  themselves  functions  of  the  x,  y and z direction to the incident light, plus the solid angle
1122          subtended by the light source (usually ignored).
1123          The data function (func) takes five variables, the
# Line 1259 | Line 1284 | well-defined, so that all components are fully compute
1284          0
1285   </pre>
1286  
1287 + <p>
1288 +
1289          The first modifier will also be used to shade  the  area  leaving the  antimatter  volume and entering the regular volume.  
1290          If mod1 is void, the antimatter volume is completely invisible.
1291          Antimatter  does  not  work  properly with the material type <a HREF="#Trans">&quot;trans&quot;</a>,
# Line 1313 | Line 1340 | A texture is a perturbation of the surface normal,  an
1340          n A1 A2 .. An
1341   </pre>
1342  
1343 + <p>
1344 +
1345   </dl>
1346  
1347   <p>
# Line 1452 | Line 1481 | A colorfunc is a procedurally  defined  color  pattern
1481                  [spacing]
1482   </pre>
1483  
1484 + <p>
1485 +
1486   or:
1487  
1488   <pre>
# Line 1489 | Line 1520 | or:
1520                  [spacing]
1521   </pre>
1522  
1523 + <p>
1524 +
1525   or:
1526  
1527   <pre>
# Line 1696 | Line 1729 | A mixfunc mixes  two  modifiers  procedurally.   It  i
1729          n A1 A2 .. An
1730   </pre>
1731  
1732 + <p>
1733 +
1734          Foreground and background are modifier names that must be
1735          defined earlier in the scene description.
1736          If one of these is a material, then
# Line 1724 | Line 1759 | A mixfunc mixes  two  modifiers  procedurally.   It  i
1759          m A1 A2 .. Am
1760   </pre>
1761  
1762 + <p>
1763 +
1764   <dt>
1765          <a NAME="Mixpict">
1766          <b>Mixpict</b>
# Line 1768 | Line 1805 | A mixfunc mixes  two  modifiers  procedurally.   It  i
1805                  [spacing]
1806   </pre>
1807  
1808 + <p>
1809 +
1810   or:
1811  
1812   <pre>
# Line 1783 | Line 1822 | or:
1822                  [spacing]
1823   </pre>
1824  
1825 + <p>
1826 +
1827   </dl>
1828  
1829   <p>
# Line 1827 | Line 1868 | An example function file is given below:
1868          cfunc(x) : 10*x / sqrt(x) ;
1869   </pre>
1870  
1871 + <p>
1872 +
1873   Many variables and functions are already defined by the program, and they are listed in the file rayinit.cal.  
1874   The following variables are particularly important:
1875  
# Line 1841 | Line 1884 | The following variables are particularly important:
1884                  arg(i)                  - i'th real argument
1885   </pre>
1886  
1887 + <p>
1888 +
1889   For mesh objects, the local surface coordinates are available:
1890  
1891   <pre>
1892                  Lu, Lv                  - local (u,v) coordinates
1893   </pre>
1894  
1895 + <p>
1896 +
1897   For BRDF types, the following variables are defined as well:
1898  
1899   <pre>
# Line 1855 | Line 1902 | For BRDF types, the following variables are defined as
1902                  CrP, CgP, CbP           - perturbed material color
1903   </pre>
1904  
1905 + <p>
1906 +
1907   A unique context is set up for each file so
1908   that  the  same variable may appear in different
1909   function files without conflict.  
# Line 1909 | Line 1958 | The basic data file format is as follows:
1958          DATA, later dimensions changing faster.
1959   </pre>
1960  
1961 + <p>
1962 +
1963   N is the number of  dimensions.  
1964   For  each  dimension,  the beginning  and  ending  coordinate  values and the dimension size is given.  
1965   Alternatively, individual coordinate  values can  be  given when the points are not evenly spaced.  
# Line 1937 | Line 1988 | All numbers are decimal integers:
1988           ...
1989   </pre>
1990  
1991 + <p>
1992 +
1993   The ASCII codes can appear in any order.  N is the number of vertices,  and  the  last  is automatically connected to the first.  
1994   Separate polygonal sections are joined by coincident sides.  
1995   The  character  coordinate  system is a square with lower left corner at (0,0), lower right at (255,0) and upper right at (255,255).
# Line 2124 | Line 2177 | OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
2177   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
2178   SUCH DAMAGE.
2179   </pre>
2180 +
2181 + <p>
2182  
2183   <hr>
2184  

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