StarfieldSimulation.gif (500 × 400 pixels, file size: 781 KB, MIME type: image/gif, looped, 240 frames, 7.2 s)
Summary
DescriptionStarfieldSimulation.gif |
English: Inspired by the "Starfield Simulation" Screensaver for Windows. (With more stars in the distance.)
Deutsch: Ähnlich zum "Starfield Simulation" Bildschirmschoner von Windows. (Mit mehr Sternen in weiter Entfernung.) |
Date | |
Source | Own work |
Author | Jahobr |
Other versions |
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GIF development InfoField | |
Source code InfoField | MATLAB codefunction StarfieldSimulation
% Source code that produces a GIF.
% Inspired by the "Starfield Simulation" Screensaver for Windows.
%
% 2017-04-20 Jahobr (update 2019-02-07 Jahobr)
[pathstr,fname] = fileparts(which(mfilename)); % save files under the same name and at file location
uniqueDepth = 200;
nFrames = 240;
renderDist = 200; % should be smaller or equal then uniqueDepth
StarDensity = 0.0005;
imageMax = [400, 500]; % pixel (height width)
subsampPix = 10; % subsampling per pixel in x and y
starRenderLimInPixel = 0.4; % diameter at least a x% of a pixel % if too small it flickers
for currentCase = 1:2
rng(1); % int rand generator to make GIF repeatable; If you dont like the GIF try a differnt value
speed = uniqueDepth/nFrames;
nStars = StarDensity*(2*renderDist * 2*renderDist * uniqueDepth);
x0 = rand(1,nStars)*renderDist*2-renderDist;
y0 = rand(1,nStars)*renderDist*2-renderDist;
sizze = 60+rand(1,nStars)*60;
sizze = [sizze sizze]; % copy space behind each other to loop the gif
depth = rand(1,nStars)*uniqueDepth;
depth = sort(depth); % makes later rendering more efficient
depth = [depth depth+uniqueDepth]; % copy space behind each other to loop the gif
switch currentCase
case 1 % classic
saveName = fname;
x_y = [x0 x0;y0 y0]; % copy space behind each other to loop the gif
thetaList = zeros(1,nFrames); % rotation
case 2 % rot 90° per gif loop
saveName = [fname '_rot'];
x_y = [x0 y0;y0 -x0]; % copy space behind each other to loop the gif
thetaList = linspace(0,pi/2,nFrames+1); % rotation
thetaList = thetaList(1:nFrames);
end
rawImage.cdata = uint8(zeros([imageMax 3]));
rawImage.colormap = [];
tic
for iFrame = 1:nFrames
disp([num2str(iFrame) ' of ' num2str(nFrames)])
image = zeros(imageMax);
%% calculate perspective
theta = thetaList(iFrame);
R = [cos(theta) -sin(theta);
sin(theta) cos(theta)];
x_y_rot = R * x_y; % rotate
plotImCoordX = (x_y_rot(1,:)./depth*imageMax(2))+imageMax(2)/2; % plane of view at depth 1; focal point at [0 0 0]
plotImCoordY = (x_y_rot(2,:)./depth*imageMax(1))+imageMax(1)/2; % plane of view at depth 1; focal point at [0 0 0]
distEuclid = sqrt( x_y_rot(1,:).^2 + x_y_rot(2,:).^2 + depth.^2 );% euclidean distance focal point at [0 0 0]
%% Rendering
% It could be done with figure and plot functions but they are not
% designed to display objects on the pixel and sub-pixel scale.
% The result just looks bad.
% So a own small rendering engine is used:
% check if a particular star rendering is necessary
% lay a grid over the star
% find if grid-points are within the star circle
% if yes, match the grid-point to a pixel and add its portion of
% "brightness" to the image
startIndex = find(depth>0,1,'first'); % depth was sorted
stopIndex = find(depth<renderDist,1,'last'); % depth was sorted
for k = startIndex:stopIndex % for all stars that would be in range
radiusStar = sizze(k)/distEuclid(k)/2;
if plotImCoordX(k)+radiusStar < 0 % outside to the left
continue % next star
end
if plotImCoordX(k)-radiusStar > imageMax(2)+1 % outside to the right
continue % next star
end
if plotImCoordY(k)+radiusStar < 0 % outside to the bottom
continue % next star
end
if plotImCoordY(k)-radiusStar > imageMax(1)+1 % outside to the top
continue % next star
end
if radiusStar*2>starRenderLimInPixel % diameter at least a defined part of a pixel
window = ceil(radiusStar *subsampPix); % size of grid to map over stars
inCircle = false(2*window,2*window);
for ix = 1:window % grid-points in positive x
for iy = 1:window % grid-points in positive y
distEuclidPixel = sqrt( ((ix-0.5)/subsampPix).^2 + ((iy-0.5)/subsampPix).^2);% euclidian distance focal point at [0 0 0]
% do a quarter of the circle and flip to -x,y and -x,-y and x,-y (1/8 would be enough actually)
if radiusStar>distEuclidPixel % is grid in reach of star
inCircle(window+ix ,window+iy ) = true; % 1 quadrant
inCircle(window+ix ,window+1-iy) = true; % 2 quadrant
inCircle(window+1-ix,window+iy ) = true; % 3 quadrant
inCircle(window+1-ix,window+1-iy) = true; % 4 quadrant
end
end
end
xGrid = round((( (1:2*window)-0.5-window) /subsampPix)+plotImCoordX(k)); % create x-grid and round to nearest Image pixel
yGrid = round((( (1:2*window)-0.5-window) /subsampPix)+plotImCoordY(k)); % create y-grid and round to nearest Image pixel
for ix = 1:2*window % pixel grid in x
if and(xGrid(ix) >= 1, xGrid(ix) <= imageMax(2)) % if in image
for iy = 1:2*window % pixel grid in y
if and(yGrid(iy) >= 1, yGrid(iy) <= imageMax(1)) % if in image
if inCircle(ix,iy) % if in Circle
image(yGrid(iy),xGrid(ix)) = image(yGrid(iy),xGrid(ix))+1/subsampPix^2; % add brightness to pixel
end
end
end
end
end
end
end
image(image>1) = 1; % fix "over exposure"
depth = depth-speed; % move
%% save animation
f = rawImage;
f.cdata(:,:,1) = uint8(image*255);
f.cdata(:,:,2) = uint8(image*255);
f.cdata(:,:,3) = uint8(image*255);
map = gray(8); % self created map. Otherwise use; [im,map] = rgb2ind(f.cdata,4,'nodither')
imtemp = rgb2ind(f.cdata,map,'nodither');
im(:,:,1,iFrame) = imtemp;
if iFrame == 1
im(1,1,1,nFrames) = 0; % allocate
end
end
toc
imwrite(im,map,fullfile(pathstr, [saveName '.gif']),'DelayTime',1/30,'LoopCount',inf) %
disp([saveName '.gif has ' num2str(numel(im)/10^6 ,4) ' Megapixels']) % Category:Animated GIF files exceeding the 50 MP limit
end
rng('shuffle'); % reset rand
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Licensing
I, the copyright holder of this work, hereby publish it under the following license:
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This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication. |
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.
http://creativecommons.org/publicdomain/zero/1.0/deed.enCC0Creative Commons Zero, Public Domain Dedicationfalsefalse |
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Wikimedia username: Jahobr
author name string: Jahobr
copyright status
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copyright license
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inception
20 April 2017
source of file
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media type
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File history
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Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 11:08, 20 April 2017 | ![]() | 500 × 400 (781 KB) | Jahobr | {{Information |Description ={{en|1=Inpired by the "Starfield Simulation" Screensaver for Windows. (With more stars in the distance.)}} {{de|1=Ählich zum "Starfield Simulation" Bildschirmschoner von Windows. (Mit mehr Sternen in weiter Entfernung)}}... |
File usage
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