這裏我用的空間是x向右為正，y向下為正，z向屏幕裏面為正。相當於標準右手系繞x軸旋轉了180度。

將三個點光源放在

r = [0.3,0,0.5];
g = [0.3,-0.5*cos(pi/6),-0.5*sin(pi/6)];
b = [0.3,0.5*cos(pi/6),-0.5*sin(pi/6)];

這三個位置上，向四周發射光線，取光線到y-z平面的模的倒數作為光的強度。

圖像如下：

程序如下：

clear all;
close all;
clc;

r = [0.3,0,0.5];
g = [0.3,-0.5*cos(pi/6),-0.5*sin(pi/6)];
b = [0.3,0.5*cos(pi/6
 
),-0.5*sin(pi/6)];
imgr1=[];imgr2=[];
imgg1=[];imgg2=[];
imgb1=[];imgb2=[];
for y=-1:0.004:1
   imgr1=[];imgg1=[];imgb1=[];
   for z=-1:0.004:1       
       pm=[0,y,z];         
       lightr=pm-r;
       lightg=pm-g;
       lightb=pm-b;
       imgr=1/norm(lightr);
       imgg=1/norm(lightg);
       imgb
 
=1/norm(lightb);
       
       imgr1=[imgr1 imgr];
       imgg1=[imgg1 imgg];      
       imgb1=[imgb1 imgb];           
   end
   imgr2=[imgr2;imgr1];
   imgg2=[imgg2;imgg1];  
   imgb2=[imgb2;imgb1]; 
end

[h w]=size(imgr2);

img=zeros(h,w,3);
img(:,:,1) = mat2gray(imgr2);
img(:,:,
 
2) = mat2gray(imgg2);
img(:,:,3) = mat2gray(imgb2);
imshow(img)
imwrite(img,‘img.png‘)

matlab練習程序（渲染三原色）