问奇数或高级语言中的射线追踪器

EN

(mat.ps) run  % load matrix library
/div { dup 0 eq { pop 10000 }{ div } ifelse } bind def  % make divide-by-zero safe
/tan { dup sin exch cos div } def 

%[vector] scalar {op}  .  [vector']
%create a new vector and fill with the scalar,
%call matrix library's vector-op
/sop {
    exch % [] {} s
    [ exch % [] {} [ s 
    3 index length 1 sub{dup}repeat % [] {} [ s*n-1
    ] exch % [] [] {}  
    vop 
} def 

/normalize { dup mag {div} sop } def 

<< % parameters
    /Cam    [ 0 0 0 ]   % camera location
    /Lookat [ 0 0 -1 ]  % camera lookat point
    /Up     [ 0 1 0 ]   % up vector
    /fovx   45          % horizontal field of view
    /W      320         % image width
    /H      200         % image height
    /Sc     [ 1 1 -5 ]  % sphere center
    /Sr     2           % sphere radius
>> begin

<< % dependent constants
    /Left Lookat Cam {sub} vop Up cross
    /buf W string
    /fovy H W div fovx mul 
    /ang 0
    /pos 3
>> {def} forall  % add these values to existing dictionary

% place the light in the scene according to the /ang parameter
/setLight { /Light [ ang cos pos mul 3 ang sin pos mul ] def } def 

0 10 360 { /ang exch def   % for-loop sets /ang, calls image and showpage
setLight                   % place the light
150 200 translate          % position lower left corner of image on page
/y 0 def                   % initial y-value
W H 8                      % put width height depth on stack  for `image` call
[ 1 0 0 1 0 0 ]            % 1-to-1 matrix, so width*height points is the image size
{                          % image procedure yields a string with one image row 
    0 1 W 1 sub { /x exch def                   % for-loop iterates over x-values
        Left   x 2 mul W sub W div fovx tan mul  {mul} sop  % construct vector from eye through center of pixel
        Up     y 2 mul H sub H div fovy tan mul  {mul} sop 
        Lookat {add} vop {add} vop 
        Cam {sub} vop 
        normalize /R exch def 

        Cam Sc {sub} vop   % use the quadratic formula to check for real intersection
        dup R dot 2 mul /B exch def 
        dup dot Sr dup mul sub /C exch def 

        B dup mul C 4 mul sub /disc exch def  % discriminant, the part under the radical-sign

        % ray hits sphere? no:0 yes:calculate
        disc 0 lt { 0 }{
            disc sqrt /sdisc exch def  % complete the quadratic formula to yield t value
            B neg sdisc sub .5 mul /t exch def
            t 0 le { B neg sdisc add .5 mul /t exch def } if
            R t {mul} sop
            Cam {add} vop /ri exch def  %intersection point
            ri Sc {sub} vop
            1 Sr div {mul} sop %normalize
            /rn exch def  %surface normal
            Light
            ri
            {sub} vop %normalize
            rn dot  % normal .dot. light-ray
            1 add .3 mul
            %.3 mul
            dup 0 lt {pop 0} if  % clip value into 8-bit range
            dup 1 gt {pop 1} if
            255 mul truncate cvi
        } ifelse   % pixel_color = 0..255

        buf x 3 2 roll put  % put pixel value in string
    } for
    /y y 1 add def  % increase y for next row
    buf  % yield string buffer to image
}
%exec  % image doesn't report internal errors, debug the procedure with `exec`
image
showpage

} bind for