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  • Adam Danz

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  • Street puddle on a rainy day in the MATropolis

on 22 Nov 2023
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drawframe(1);
Write your drawframe function below
function drawframe(f)
% Persistent variable definitions
% CD: CData of full city reflection image
% R: surface object for the city image in the puddle reflection
persistent CD R
if f==1
%% Create city reflection (variable CD)
rng default
axes(colorm=gray,Color='k',Projection='perspective')
hold on
h=randg(2,5,5); % building heights
b=bar3(h); % buildings
set(b,{'CData'},get(b,'ZData'),{'FaceColor'},{'interp'}) % lighter at top
b(3).delete % remove a row of buildings
% Set up axes and field of view
axis equal
clim([0,3])
campos([3,3,0])
camtarget([4 3 6])
camva(90)
camup([-1 0 0])
% loop through the buildings to add windows
for i=1:5
for j=[1 2 4 5]
s=(j<3)*.82-.41; % which side of the building will be windows be on
c=.1:.2:h(i,j)-.2;
d=[c;c];
z=d(:)'+[0;0;.1;.1];
y=i+[-.2,.2]+[-1;1;1;-1]/12;
y=repmat(y,size(c));
ison=logical(rand(1,numel(d))>0.4);
patch(z(:,ison)*0+j+s,y(:,ison),z(:,ison),[.48 .46 .17]); % Lights on
patch(z(:,~ison)*0+j+s,y(:,~ison),z(:,~ison),[.2 .2 .3]); % Lights off
end
end
% Create coherent noise for clouds
m=400;
X=linspace(-1,1,m);
d=hypot(X,X').^-1.7;
fr=fftshift(fft2(rand(m)));
sd=ifft2(ifftshift(fr.*d));
% Scale the noise to within the clim
cl=rescale(abs(sd),0,2);
% Plot cloudy sky; x and y extents will be large due to perspective
w=linspace(-20,30,m);
surf(w,w,max(h(:))+ones(m)-.9,FaceColor='texturemap',EdgeColor='none',CData=cl);
% capture image
fr=getframe;
CD=flipud(fr.cdata); % Take a peek: clf; imagesc(CD); set(gca,'YDir','normal')
%% Iterate the buffer to the 48th frame so we start with the end-state
% This will simulate the entire 48-frame animation and use the updated
% image as a starting point so the animation cycles (because Ned keeps
% praising animations that cycle :D)
rng(860411,'twister')
G=rng;
updatebuf(CD,1);
for i=2:48
updatebuf(CD,0);
end
%% Create street terrain
rng(790316,'twister') % This seed makes a nice puddle
n=1000; % determines size of the final image
X=linspace(-1,1,n); %create linear r matrix
[~,r]=cart2pol(X,X');
rd=rand(n);
filt=r.^-2.5; % roughness of puddle edges -- 2.5 is great,2.0-edges are too rough
fr=fftshift(fft2(rd));
td=ifft2(ifftshift(fr.*filt));
st=-rescale(abs(td),-0.2,0); % This scales from 0 to .2
wlev=0.13; % Water level; 0.12 and 0.13 look good
%% Plot street terrain
clf % clear figure
g=rescale(imgaussfilt(rand(n),2),0,1); % street texture
surf(1:n,1:n,st,FaceColor='texturemap',CData=g,EdgeColor='none'); % street
hold on
view(2)
colormap gray
set(gca,'Position',[0 0 1 1])
%% Initialize puddle reflection (variable R)
% add the city image and water level depth
u=size(CD);
R=surf(linspace(0,n,u(1)),linspace(0,n,u(2)),zeros(u([2,1]))+wlev,...
FaceColor='Texturemap',EdgeColor='none',CData=CD);
clim([0,1])
%% Return random number generator state to replicate ripples
% This must be at the end of setup
rng(G)
end
% Update ripples and rain drops on each iteration
[xo,yo]=updatebuf(CD,0);
R.CData=updateCD(CD,xo,yo);
end
function [xo,yo]=updatebuf(CD,TF)
% Update buffers
persistent b1 b2
[r,c]=size(CD,1:2); % reflection image size
if TF || isempty(b1)
% Create buffers that map ripples on to the image on first call
b1=zeros(r,c);
b2=b1;
end
% Animation: add rain drops
% Set up some variables that won't change between iterations
d=1/36; % dampening parameter determins how quickly the ripples fade,lower values last longer
M=zeros(3); % mask
M(2:2:end)=1;
xM=[-1 0 1];
yM=[-1;0;1];
[x,y]=meshgrid(1:c,1:r);
% On each frame there is a probability of there being a new rain drop
if rand<.2 % increase threshold to increase frequency of new drops
xp=randi(c);
yp=randi(r);
startX=max(1,xp-10);
startY=max(1,yp-10);
b2(startY:yp,startX:xp)=-randi(100);
end
% Propagate the ripples
for k=1:3
b2=filter2(M,b1)/2 - b2;
b2=b2 - b2*d;
xo=min(c,max(1,x+filter2(xM,b2))); % x-offset bounded by [1,c]
yo=min(r,max(1,y+filter2(yM,b2))); % y-offset bounded by [1,r]
% Swap buffers
tmp=b2;
b2=b1;
b1=tmp;
end
end
function I=updateCD(CD,xo,yo)
% Create the a new image by applying the buffer offsets to the old image CData
f=@(i)interp2(double(CD(:,:,i)),xo,yo);
I(:,:,1)=f(1);
I(:,:,2)=f(2);
I(:,:,3)=f(3);
I=uint8(I);
end
Animation
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