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  • Ring world

on 11 Nov 2023
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drawframe(1);
Write your drawframe function below
function drawframe(f)
% Ring world...
persistent H CS S3 U
if f==1
rng(2,'v4')
% % % % Make the ring % % % %
r=6; % Radius
N=60; % Number of edge-pixels on base unit
U=8; % Rotating by 1/8 of a circle
% Add texture to ring. Make it tech-y
R=zeros(N,N);
R(randi(N^2, 3))=1;
k1=ones(N/2)/10;
k2=k1;
k2(2:end-1,2:end-1)=0; % Kernel for glowing lights
RL=conv2(R,k2,'same'); % Glowing lights
R=conv2(R,k1,'same'); % Surface
% Tiling
R=repmat(R,[1,U])+1;
RL=repmat(RL,[1,U]);
% Fix seams. Expendable code.
R=s(R,N);
RL=s(RL,N);
RB=(R-1)/2;
RL=RL./RL;
% Notch to fit the land in...
NH=N/2;
NW=floor(N/6);
R(NH-NW+1:NH+NW, :)=0;
% Make our angles
l=@(x)linspace(0,2*pi,x);
ag1=l(N)';
a=l(N*U);
c=cos(a);
v=sin(a);
% Ring torus
b=erf(R.*cos(ag1)*5)+RB; % Make it square-ish
z=R.*sin(ag1);
x=b.*c+r*c;
y=b.*v+r*v;
% % % % Make the land inside.
% Spectral noise shaping... land mass will be a noisy cylinder
q=linspace(-1,1,N);
rand(8);
k=@()exp(6i*randn(N))./(q.^2+q'.^2+2e-4);
oo=@(x)ifft2(x);
B=rescale(abs(oo(k())))-.3;
CS=k();
C=rescale(abs(real(oo(CS.*exp(1i*.10)))))-.5;
X=@(x)max(repmat(x,[1,U])',0);
B=X(B)/2; % Max makes the water
C=X(C); % Clouds
% Assemble the cylinder s
[xl,yl,zl]=cy(a',q,r-B/3-.6,N); % Land
[xc,yc,zc]=cy(a',q,r+0*B-1.1,N); % Cloud
[xa,ya,za]=cy(a',q,r+0*B-1,N); % Atmosphere
za=za*1.1;
% Custom colormap: landscapey with low value = blue = water
cmp=max(copper,summer);
cmp(1,:)=[.1,.3,1]/2;
% Now plot
H=hgtransform();
surf(x,z,y,'pa',H); % Ring
material([0,.1,.6,3]);
hold on;
surf(x,z,y,RL.*cat(3,0,1,1),'AmbientS',1,'pa',H); % Light
hold on;
% Land, clouds, atmosph
S=surf(xl,zl,yl,B,'pa',H);
wn=sin(ag1/2);
alph =(1-wn).^3'.*ones(N*U, 1);
cp = rescale(alph, 0.7, 1);
cp = cat(3, cp.^8, cp.^2.5, cp.^0.9);
mm=@(x,y)material(x,y);
S3=surf(xc,zc,yc,0*xc+cat(3,1,1,1),'FaceAlpha','flat','AlphaData',erf(C*4),'pa',H);
S2=surf(xa,za,ya,cp,'FaceAlpha','flat','AlphaData',alph.^.7);
mm(S3,[1,0,0,5]);
mm(S2,[.6,1,0,5]);
mm(S,[0,1,.3,20]);
colormap(cmp);
caxis([0,.3]);
axis equal
shading flat
% Add stars
x=randn(3,900);
x=x./vecnorm(x)*20;
scatter3(x(1,:),x(2,:),x(3,:),rand(900,1)*100,rand(900,1)*[1,1,1],'.');
hold off;
% Axis / camera etc.
shading flat
axis equal off
light('position',[0,-20,0]);
light('position',[10,10,5]);
lighting('gouraud');
shading flat
set(gcf,'color','k');
camproj('perspective')
camva(30);
campos([78, -40, -40]/6);
camtarget([-1, 0, -1]);
end
ags=linspace(0,2*pi,49);
oo=@(x)ifft2(x);
C=rescale(abs(real(oo(CS.*exp(1i*ags(f))))))-.5;
X=@(x)max(repmat(x,[1,U])',0);
C=X(C); % Clouds
campos([78,-40+sin(ags(f))*2,-40]/6)
S3.AlphaData=erf(C*4);
set(H,'Ma', makehgtform('yrotate',(f-1)*pi/4/48));
end
% Extra functions:
% Make xyz cylinder coordinates
function [x,y,z]=cy(a,q,R,N)
x=cos(a).*R;
y=sin(a).*R;
z=q.*ones(N*8,1)*.9;
end
% Seam joiner
function g=s(g,N)
d=g(N,:)/2+g(1,:)/2;
g(1:4, :) = d.*ones(4,1);
g(end-3:end,:) = d.*ones(4,1);
end
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