rays2img.m

function [img,x,y] = rays2img(rays_x,rays_y,width,Npixels)
% rays2img - Simulates the operation of a camera sensor, where each pixel
% simply collects (i.e., counts) all of the rays that intersect it. The
% image sensor is assumed to be square with 100% fill factor (no dead
% areas) and 100% quantum efficiency (each ray intersecting the sensor is
% collected).
%
% inputs:
% rays_x: A 1 x N vector representing the x position of each ray in meters.
% rays_y: A 1 x N vector representing the y position of each ray in meters.
% width: A scalar that specifies the total width of the image sensor in 
%   meters.
% Npixels: A scalar that specifies the number of pixels along one side of 
%   the square image sensor.
%
% outputs:
% img is an Npixels x Npixels matrix representing a grayscale image captured by 
% an image sensor with a total Npixels^2 pixels.
% x: A 1 x 2 vector that specifies the x positions of the left and right 
%   edges of the imaging sensor in meters.
% y: A 1 x 2 vector that specifies the y positions of the bottom and top 
%   edges of the imaging sensor in meters.
%
% Matthew Lew 11/27/2018
% 11/26/2021 - edited to create grayscale images from a rays_x, rays_y
% vectors

% eliminate rays that are off screen
onScreen = abs(rays_x)<width/2 & abs(rays_y)<width/2;
x_in = rays_x(onScreen);
y_in = rays_y(onScreen);

% separate screen into pixels, calculate coordinates of each pixel's edges
mPerPx = width/Npixels;
Xedges = ((1:Npixels+1)-(1+Npixels+1)/2)*mPerPx;
Yedges = ((1:Npixels+1)-(1+Npixels+1)/2)*mPerPx;

% count rays at each pixel within the image
img = histcounts2(x_in,y_in,Xedges,Yedges);


% rescale img to uint8 dynamic range
img = uint8(round(img/max(img(:)) * 255));
x = Xedges([1 end]);
y = Yedges([1 end]);

% figure;
% image(x_edges([1 end]),y_edges([1 end]),img); axis image xy;
end