#!F-adobe-helvetica-medium-r-normal--18*
#!N 
#!CSeaGreen 
#!N  #!Rrendmdl Rendering Model #!N #!EC #!N #!N The interpretation of 
"colors" and "opacities" differs between surfaces and volumes. For surfaces, a 
surface of color  #!F-adobe-times-medium-i-normal--18*   c[f] #!EF and opacity  #!F-adobe-times-medium-i-normal--18*   o #!EF 
are combined with the color  #!F-adobe-times-medium-i-normal--18*   c[b] #!EF of the objects 
behind it, resulting in a combined color  #!F-adobe-times-medium-i-normal--18*   c[f]o + c[b] 
(1 - o) #!EF . #!N #!N For volumes, the "dense 
emitter" model is used, in which the opacity represents the instantaneous 
rate of absorption of light passing through the volume per unit 
thickness, and the color represents the instantaneous rate of light emission 
per unit thickness. If  #!F-adobe-times-medium-i-normal--18*   c(z) #!EF represents the color of 
the object at  #!F-adobe-times-medium-i-normal--18*   z #!EF and  #!F-adobe-times-medium-i-normal--18*   o(z) #!EF represents 
its opacity at  #!F-adobe-times-medium-i-normal--18*   z #!EF , the total color  #!F-adobe-times-medium-i-normal--18*   
c #!EF of a ray passing through the volume is given 
by: #!N c = integral to infinity from - infinity c 
( z ) 'exp' (- integral to z from - infinity 
o ( zeta ) d zeta) dz #!N #!N #!N #!N 
 #!F-adobe-times-medium-i-normal--18*   Next Topic #!EF #!N #!N  #!Lall1133,dxall1134 h Tiling Options  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   #!N 
