O Christmas Tree

on 1 Dec 2023

drawframe(40);

function drawframe(f)

% This is Xor's AMAZING shader

% https://www.shadertoy.com/view/7lKSzw

% Here is my translation to MATLAB

iRes = 300;

iTime = f/48*2;

persistent fragCoord

if isempty(fragCoord)

[x,y]=meshgrid(1:iRes, 1:iRes);

fragCoord = cat(3,x,flip(y,1));

end

im = mainImage(fragCoord);

im = imresize(im, [3*iRes, 3*iRes], 'method', 'bilinear');

imshow(im);

axis equal

axis off

%% magic

function finalColor = mainImage(fragCoord)

finalColor = zeros(iRes, iRes, 3);

r = cat(3,iRes,iRes);

for i=0:400

if mod(i,8) < 6

even = mod(i,2);

c = [even,1- even,0];

else

c = [1 1 1];

end

p = (fragCoord.* 2 - r)./r(:,:,2).*300 + cat(3,0,i-230)....

+ cat(3,i+mod(i,99),i/4).*cos(iTime.*0.5+cat(3,i,i+11)).*0.5;

for j = 1:3

finalColor(:,:,j) = finalColor(:,:,j) + c(j)./vecnorm(p,2,3).^2;

end

finalColor = sqrt(finalColor./0.1);

end