A tiny simplistic python raytracer based on a BBC BASIC program https://twitter.com/bbcmicrobot/status/1464585083109707776

raytracer1_for_twitter.py

# An attempt to port this https://twitter.com/bbcmicrobot/status/1464585083109707776 from BBC Basic to python
# To understand how it works and maybe attempt to write something similar in 65816 assembly (SNES)

# License for my part of the code is MIT, cannot speak for the many people that worked on the original BBC BASIC version though.
# Requires the python modules PIL or Pillow for image output. Outputs a 8 bit monochrome PNG image.

from PIL import Image, ImageOps
import math

# Set up image
img=Image.new("L",(320,256))


# Pixel Plot loops
for pix_y in range(img.size[1]):
    for pix_x in range(img.size[0]):

        #Camera Position
        X=0
        Y=-0.1
        Z=3

        #Camera Rotation
        U=(pix_x-(img.size[0]/2)-0.5)/(img.size[0]/2) # Replaced the hardcoded image dimensions with variables here so that the resolution can easily be changed
        V=(pix_y-(img.size[1]/2)-0.5)/(img.size[0]/2)
        W=1/math.sqrt(U*U+V*V+1)

        #Perspective projection (?)
        U=U*W
        V=V*W
        I = (-1,1)[U > 0]  # Ternary operator replacing the "SGN" command

        while(True): #Infinite loop with break and continue replacing GOTO
            E=X-I
            F=Y-I
            P=U*E+V*F-W*Z

            # Spheres (?)
            D=P*P-E*E-F*F-Z*Z+1
            if D>0:
                T=-P-math.sqrt(D)
                if T>0:
                    X=X+T*U
                    Y=Y+T*V
                    Z=Z-T*W
                    E=X-I
                    F=Y-I
                    G=Z
                    P=2*(U*E+V*F-W*G)
                    U=U-P*E
                    V=V-P*F
                    W=W+P*G
                    I=-I
                    continue
            break
                
        # Ground Checkerboard
        if V<0:
            P=(Y+2)/V
            V=-V*((int(X-U*P)+int(Z-W*P) & 1)/2+.3)+.2                

        img.putpixel((pix_x,pix_y),int(255-V*255)) # Original has a backwards palette so i am inverting the pixels by subtracting them from the max brightness



img=ImageOps.flip(img) #Original plots from bottom, so image should be flipped
img.save("output.png")