#!F-adobe-helvetica-medium-r-normal--18*
#!N 
#!CNavyBlue #!N  #!Rall1130 Surface 
Shading #!N #!EC #!N #!N Shading is the process of applying 
lights to a surface according to shading parameters specified for the 
surface and the scene. #!N #!N The shading process described here 
is performed by the  #!F-adobe-times-bold-r-normal--18*   DXRender() #!EF function for surface objects 
only; volumes are rendered directly, using the colors and opacities specified. 
Lights are specified by light Objects (see  #!Llightsc,dxall1139 h Light Class  #!EL  ) contained in 
the input Object. Shading is defined only for 2-dimensional connections (lines, 
triangles, and quads) and is applied only if normals are present. 
The shading process uses the following Field components: #!T,1,51,151  #!F-adobe-times-bold-r-normal--18*   #!N 
TAB Componen| Meaning #!EF #!N TAB "positio|spoints #!N TAB "colors"| front 
and back #!N TAB - TAB colors #!N TAB "front TAB 
colors of front #!N TAB colors" TAB of face #!N TAB 
"back TAB colors of back #!N TAB colors" TAB of face 
#!N TAB "normals| surface normals #!N #!N A Field may have 
both "colors" and "front colors" or both "colors" and "back colors," 
in which case the "front colors" or "back colors" component overrides 
the "colors" component for the specified side of the object. The 
front and back of a surface are defined in  #!Ldatmod,dxall197 h Understanding the Data Model  #!EL  in 
IBM Visualization Data Explorer User's Guide. #!N #!N Shading parameters are 
specified by a set of attributes of an input Object: #!T,1,51,151 
 #!F-adobe-times-bold-r-normal--18*   #!N TAB Attribut| Meaning #!EF #!N TAB "ambient| ambient lighting 
#!N TAB - TAB coefficient k[a] #!N TAB "diffuse| diffuse lighting 
#!N TAB - TAB coefficient k[d] #!N TAB "specula|"specular #!N TAB 
- TAB lighting #!N TAB - TAB coefficient k[s] #!N TAB 
"shinine|sspecular #!N TAB - TAB lighting #!N TAB - TAB exponent 
sp #!N #!N These parameters apply to both the front and 
back of an object. In addition, for each shading parameter " 
 #!F-adobe-times-medium-i-normal--18*   x #!EF ," there is also a "front  #!F-adobe-times-medium-i-normal--18*   x 
#!EF " and a "back  #!F-adobe-times-medium-i-normal--18*   x #!EF " parameter that 
apply only to the front and back of a surface respectively. 
These parameters are used in the following shading model: #!N I 
= k sub a A C + k sub d L 
C ( #!EF n #!EF dot  #!F-adobe-times-bold-r-normal--18*   l #!EF ) + 
k sub s L (  #!F-adobe-times-bold-r-normal--18*   n #!EF dot  #!F-adobe-times-bold-r-normal--18*   h 
#!EF )**sp #!N #!N #!N where: #!N  #!F-adobe-times-medium-i-normal--18*   I #!EF = 
apparent intensity of the object  #!F-adobe-times-medium-i-normal--18*   k #!EF = a lighting 
coefficient  #!F-adobe-times-medium-i-normal--18*   A #!EF = an ambient light  #!F-adobe-times-bold-r-normal--18*   n #!EF 
= the surface normal  #!F-adobe-times-medium-i-normal--18*   C #!EF = the color of 
the object  #!F-adobe-times-bold-r-normal--18*   l #!EF = the direction to the light 
 #!F-adobe-times-medium-i-normal--18*   L #!EF = a point or distant light  #!F-adobe-times-medium-i-normal--18*   sp 
#!EF = specular lighting exponent  #!F-adobe-times-bold-r-normal--18*   h #!EF = a unit 
vector halfway between the direction to the camera and the direction 
to the light. #!CIndianRed #!N #!N #!N  #!F-adobe-times-bold-r-normal--18*   Color, Opacity, and 
Normals Dependencies #!N #!N Colors, opacities, and normals may be dependent 
on the positions (when the corresponding components have a "dep" attribute 
of "positions") or on connections or faces (when the corresponding components 
have a "dep" attribute of "connections" or "faces"). #!N #!N Opacities 
and normals, if present, must depend on the same component that 
the colors depend upon, with one exception: if the colors are 
dependent on the positions and the normals are dependent on the 
connections, the face will be flat-shaded with the average color of 
the face vertices. #!N #!N If the colors, opacities, and normals 
are dependent on the positions, the color and opacity of each 
face is linearly interpolated between the vertices (Gouraud shading). If they 
are dependent on the connections or faces, the color and opacity 
of each face is constant (flat shading). #!N #!N #!EC #!N 
#!N #!N  #!F-adobe-times-medium-i-normal--18*   Next Topic #!EF #!N #!N  #!Lall1131,dxall1132 h Tiling  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   
#!N 
