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Revision 1.39 by greg, Mon Dec 9 19:21:38 2024 UTC vs.
Revision 1.41 by greg, Thu May 29 16:42:28 2025 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 580 | Line 586 | This is only appropriate if the surface hides other (m
586          3 red green blue
587   </pre>
588  
589 + While alternate materials that are reflective will appear as normal,
590 + indirect rays will use the mirror's reflectance rather than the
591 + alternate type.
592 + Transmitting materials are an exception, where both transmission and
593 + reflection will use the alternate type for all rays not specifically
594 + targeting virtual light sources.
595 + Therefore, transmitting alternate types should only have pure specular
596 + reflection if they reflect at all, to maintain a valid calculation.
597 +
598   <p>
599  
600 + The mirror material type reflects light sources only from the front side
601 + of a surface, regardless of any alternate material.
602 + If virtual source generation is desired on both sides, two coincident
603 + surfaces with opposite normal orientations may be employed to achieve
604 + this effect.
605 + The reflectance and alternate material type may be
606 + different for the overlapped surfaces,
607 + and the two sides will behave accordingly.
608 +
609 + <p>
610 +
611   <dt>
612          <a NAME="Prism1">
613          <b>Prism1</b>
# Line 603 | Line 629 | This is only appropriate if the surface hides other (m
629          n A1 A2 .. An
630   </pre>
631  
632 + <p>
633 +
634          The new direction variables dx, dy and dz need not produce a normalized  vector.  
635          For convenience, the variables DxA, DyA and DzA are defined as the normalized direction to the  target  light  source.  
636          See <a HREF="#Function">section 2.2.1</a> on function files for further information.
# Line 646 | Line 674 | This is only appropriate if the surface hides other (m
674          3  source1  mirror1&gt;source10  mirror2&gt;mirror1&gt;source3
675   </pre>
676  
677 + <p>
678   Normally, only one source is given per mist material, and there is an
679   upper limit of 32 to the total number of active scattering sources.
680   The extinction coefficient, if given, is added the the global
# Line 666 | Line 695 | forward direction, as fit by the Henyey-Greenstein fun
695          P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5
696   </pre>
697  
698 + <p>
699 +
700   A perfectly isotropic scattering medium has a g parameter of 0, and
701   a highly directional material has a g parameter close to 1.
702   Fits to the g parameter may be found along with typical extinction
# Line 680 | Line 711 | cloud types in USGS meteorological tables.
711          0|3|6|7 [ rext gext bext [ ralb galb balb [ g ] ] ]
712   </pre>
713  
714 + <p>
715 +
716   There are two usual uses of the mist type.
717   One is to surround a beam from a spotlight or laser so that it is
718   visible during rendering.
# Line 857 | Line 890 | unless the line integrals consider enclosed geometry.
890              A10 ..
891   </pre>
892  
893 + <p>
894 +
895   The sum of specular reflectance (<I>rs</I>), specular transmittance (<I>ts</I>),
896   diffuse reflectance (<I>rfdif gfdif bfdif</I> for front and <I>rbdif gbdif bbdif</I> for back)
897   and diffuse transmittance (<I>rtdif gtdif btdif</I>) should be less than 1 for each
# Line 950 | Line 985 | well-defined, so that all components are fully compute
985          tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn
986   </pre>
987  
988 + <p>
989 +
990          Standard 88% transmittance glass  has  a  transmissivity  of 0.96.  
991          (A <a HREF="#Patterns">pattern</a> modifying glass will affect the transmissivity.)
992          If a fourth real argument is given,  it  is  interpreted as the index of refraction to use instead of 1.52.
# Line 981 | Line 1018 | well-defined, so that all components are fully compute
1018          4+ red green blue spec A5 ..
1019   </pre>
1020  
1021 + <p>
1022 +
1023          The function refl takes four arguments, the x, y and z
1024          direction towards the incident light, and the solid angle
1025          subtended by the source.
# Line 1022 | Line 1061 | well-defined, so that all components are fully compute
1061          6+ red green blue rspec trans tspec A7 ..
1062   </pre>
1063  
1064 + <p>
1065 +
1066          Where trans is the total light transmitted and tspec is  the non-Lambertian  fraction of transmitted light.  
1067          The function brtd should integrate to 1 over each projected hemisphere.
1068  
# Line 1049 | Line 1090 | well-defined, so that all components are fully compute
1090               A10 ..
1091   </pre>
1092  
1093 + <p>
1094 +
1095          The variables rrefl, grefl and brefl specify the color coefficients  for  the ideal specular (mirror) reflection of the surface.  
1096          The variables rtrns, gtrns and btrns  specify  the color coefficients for the ideal specular transmission.  
1097          The functions rbrtd, gbrtd and bbrtd take the direction to the incident light (and its solid angle) and  
# Line 1093 | Line 1136 | well-defined, so that all components are fully compute
1136          4+ red green blue spec A5 ..
1137   </pre>
1138  
1139 + <p>
1140 +
1141          The coordinate indices (x1, x2, etc.) are  themselves  functions  of  the  x,  y and z direction to the incident light, plus the solid angle
1142          subtended by the light source (usually ignored).
1143          The data function (func) takes five variables, the
# Line 1259 | Line 1304 | well-defined, so that all components are fully compute
1304          0
1305   </pre>
1306  
1307 + <p>
1308 +
1309          The first modifier will also be used to shade  the  area  leaving the  antimatter  volume and entering the regular volume.  
1310          If mod1 is void, the antimatter volume is completely invisible.
1311          Antimatter  does  not  work  properly with the material type <a HREF="#Trans">&quot;trans&quot;</a>,
# Line 1313 | Line 1360 | A texture is a perturbation of the surface normal,  an
1360          n A1 A2 .. An
1361   </pre>
1362  
1363 + <p>
1364 +
1365   </dl>
1366  
1367   <p>
# Line 1452 | Line 1501 | A colorfunc is a procedurally  defined  color  pattern
1501                  [spacing]
1502   </pre>
1503  
1504 + <p>
1505 +
1506   or:
1507  
1508   <pre>
# Line 1489 | Line 1540 | or:
1540                  [spacing]
1541   </pre>
1542  
1543 + <p>
1544 +
1545   or:
1546  
1547   <pre>
# Line 1696 | Line 1749 | A mixfunc mixes  two  modifiers  procedurally.   It  i
1749          n A1 A2 .. An
1750   </pre>
1751  
1752 + <p>
1753 +
1754          Foreground and background are modifier names that must be
1755          defined earlier in the scene description.
1756          If one of these is a material, then
# Line 1724 | Line 1779 | A mixfunc mixes  two  modifiers  procedurally.   It  i
1779          m A1 A2 .. Am
1780   </pre>
1781  
1782 + <p>
1783 +
1784   <dt>
1785          <a NAME="Mixpict">
1786          <b>Mixpict</b>
# Line 1768 | Line 1825 | A mixfunc mixes  two  modifiers  procedurally.   It  i
1825                  [spacing]
1826   </pre>
1827  
1828 + <p>
1829 +
1830   or:
1831  
1832   <pre>
# Line 1783 | Line 1842 | or:
1842                  [spacing]
1843   </pre>
1844  
1845 + <p>
1846 +
1847   </dl>
1848  
1849   <p>
# Line 1827 | Line 1888 | An example function file is given below:
1888          cfunc(x) : 10*x / sqrt(x) ;
1889   </pre>
1890  
1891 + <p>
1892 +
1893   Many variables and functions are already defined by the program, and they are listed in the file rayinit.cal.  
1894   The following variables are particularly important:
1895  
# Line 1841 | Line 1904 | The following variables are particularly important:
1904                  arg(i)                  - i'th real argument
1905   </pre>
1906  
1907 + <p>
1908 +
1909   For mesh objects, the local surface coordinates are available:
1910  
1911   <pre>
1912                  Lu, Lv                  - local (u,v) coordinates
1913   </pre>
1914  
1915 + <p>
1916 +
1917   For BRDF types, the following variables are defined as well:
1918  
1919   <pre>
# Line 1855 | Line 1922 | For BRDF types, the following variables are defined as
1922                  CrP, CgP, CbP           - perturbed material color
1923   </pre>
1924  
1925 + <p>
1926 +
1927   A unique context is set up for each file so
1928   that  the  same variable may appear in different
1929   function files without conflict.  
# Line 1909 | Line 1978 | The basic data file format is as follows:
1978          DATA, later dimensions changing faster.
1979   </pre>
1980  
1981 + <p>
1982 +
1983   N is the number of  dimensions.  
1984   For  each  dimension,  the beginning  and  ending  coordinate  values and the dimension size is given.  
1985   Alternatively, individual coordinate  values can  be  given when the points are not evenly spaced.  
# Line 1937 | Line 2008 | All numbers are decimal integers:
2008           ...
2009   </pre>
2010  
2011 + <p>
2012 +
2013   The ASCII codes can appear in any order.  N is the number of vertices,  and  the  last  is automatically connected to the first.  
2014   Separate polygonal sections are joined by coincident sides.  
2015   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 2197 | OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
2197   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
2198   SUCH DAMAGE.
2199   </pre>
2200 +
2201 + <p>
2202  
2203   <hr>
2204  

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