Quartz_Through_the_Microscope.m

animateFrames();
function animateFrames()
    animFilename = 'Quartz_Through_the_Microscope.gif'; % Output file name
    firstFrame = true;
    framesPerSecond = 24;
    delayTime = 1/framesPerSecond;

    % Create the gif
    for frame = 1:48
        drawframe(frame);
        fig = gcf();
        fig.Units = 'pixels';
        fig.Position(3:4) = [300,300];
        im = getframe(fig);
        [A,map] = rgb2ind(im.cdata,256);

        if firstFrame
            firstFrame = false;
            imwrite(A,map,animFilename, 'LoopCount', Inf, 'DelayTime', delayTime);
        else
            imwrite(A,map,animFilename, 'WriteMode', 'append', 'DelayTime', delayTime);
        end
    end
end
function drawframe(f)
    % yay geology :D
    % looking at quartz through a petrographic microscope!
    % when you rotate a thin section (a slice of rock ~35 µm thick, mounted
    %  on a slide) in cross-polarized light, many minerals change color!
    % these color changes are caused by light getting bounced around the
    %  mineral's crystal lattice; geologists more skilled at optical
    %  mineralogy than i am can use these color changes, along with a
    %  variety of other properties, to determine the mineral composition of
    %  rocks in thin section.
    % quartz (SiO2) is one of the easiest and most important sedimentary rock-forming
    %  minerals to identify through a petrographic microscope; it's perhaps most easily
    %  distinguished by its extinction from black to whitish to black when you rotate
    %  the slide 90º.
    % learn more:
    % http://microckscopic.ro/minerals/silicates/tectosilicates/quartz-thin-section/
    % https://www.ucl.ac.uk/~ucfbrxs/MoreMinerals/Quartz.html
    % https://www.youtube.com/watch?v=r0RPz0i7Rww
    
    close
    th = f*150/48;
    rt = [cosd(th) -sind(th); sind(th) cosd(th)];
    
    % i actually drew out the crystals by hand so i could keep track of
    %  vertices
    % they're all hexagons bc that seemed easier
    % even rows x, odd rows y; start at top/top right corner and work cw
    % xl = crystal btw
    xls = [4   5  4  1  0  1; % xl1x
           10  9  7  6  7  8; % xl1y
           -5 -4 -4 -5 -6 -6; % xl2x
           11 10  7  6  8 10; % xl2y
           7   8  9  9  5  5; % xl3x
           9   6  6  1  1  9; % xl3y
           0   2  0 -2 -3 -3; % xl4x
           2   0 -2 -2 -1  2; % xl4y
           -2 -1 -1 -3 -4 -4; % xl5x
           11 10  7  6  7 10; % xl5y
           -5 -3 -3 -5 -7 -7; % xl6x
           4   2 -1 -1  1  2; % xl6y
           -5 -3 -3 -4 -6 -9; % xl7x
           -4 -6 -7 -8 -7 -6; % xl7y
           3   4  2 -2  0  2; % xl8x
           -5 -6 -9 -9 -7 -6; % xl8y
           9   6  4  5  4  5; % xl9x
           1  -2 -3 -1  0  1; % xl9y 
           5   5  4  2  0  2; % xl10x
           5   1  0  0  2  3; % xl10y
           9  10  9  7  7  6; % xl11x
           1  -2 -6 -6 -3 -2; % xl11y
           1   4  1  0 -1 -1; % xl12x
           11 10  8  7  7 10; % xl12y
           -7 -5 -5 -9 -9 -9; % xl13x
           1  -1 -4 -6 -3 -1; % xl13y
           -6 -5 -5 -7 -8 -8; % xl14x
           8   6  4  2  4  6; % xl14y
           -8 -7 -7 -9 -10 -10; % xl15x
           4   2  1 -1  1  2; % xl15y
           0   2  0 -3 -4 -3; % xl16x
           4   3  2  2  3  4; % xl16y
           -3 -2 -2 -3 -5 -5; % xl17x
           -1 -2 -4 -6 -4 -1; % xl17y
           -2  0 -2 -4 -3 -3; % xl18x
           -4 -7 -9 -8 -7 -6; % xl18y
           0   3  2  0 -2 -2; % xl19x
           -2 -5 -6 -7 -4 -2; % xl19y
           4   5  4  1  0  2; % xl20x
           0  -1 -3 -3 -2  0; % xl20y
           0   1  0 -3 -3 -1; % xl21x
           7   6  4  4  6  7; % xl21y
           6   7  7  4  1  4; % xl22x
           -2 -3 -6 -6 -3 -3; % xl22y
           5   5  2  0  1  4; % xl23x
           9   5  3  4  6  7; % xl23y
           7   6  5  4  2  4; % xl24x
           -6 -8 -8 -9 -9 -6; % xl24y
           -4 -3 -3 -4 -5 -5; % xl25x
           7   6  4  3  4  6]; % xl25y
    
    % now plot 
    for i = 1:2:max(size(xls))
        % rotate
        xl = xls(i:i+1,:)'*rt;
        color = 0.95*abs(sind(th*2+(i*180/24)))*[1 1 1]+0.01; % changes the color to fit the rotation
       
        patch(xl(:,1), xl(:,2), color, 'LineWidth', 0.25) % the grains kinda do actually have lines in between them irl which is really nice
        hold on
    end
    
    % this was the easiest way i could figure out how to make a black
    %  background while leaving the middle clear
    % sue me lol
    px = zeros(1,14996);
    py = zeros(1,14996);
    idx = 1;
    for i = 0:0.1:10
        for j = 0:0.1:10
            if i^2 + j^2 > 81
                px(idx) = i; py(idx) = j;
                px(idx+1) = i; py(idx+1) = -j;
                px(idx+2) = -i; py(idx+2) = -j;
                px(idx+3) = -i; py(idx+3) = j;
                idx = idx+4;
            end 
        end
    end
    
    % set up the background
    plot(px, py, '.k')
    hold on
    plot([0 0], [-10 10], '-k', 'LineWidth', 0.1)
    hold on
    plot([-10 10], [0 0], '-k', 'LineWidth', 0.1)
    xticks([]); yticks([]); xlabel([]); ylabel([]);
    xlim([-10 10]); ylim([-10 10])
 
    % keep an eye out for calcite through the microscope as soon as i can
    %  get the animation to run! lol
end