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  • Matlon5's evil twin

on 30 Nov 2023
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drawframe(1);
Write your drawframe function below
function drawframe(f)
% Cloudy planet
% Thanks to Vinay for extending the compiling time limit!
persistent T T2 H pn H2
if f==1
rng(9,'twister');
% Some shorteners
u=@rescale;
v=@vecnorm;
rn=@(x)rand(x,1)/3+1;
% % % Creating the clouds
% Create a Fibonacci sphere with 5e4 points
n1=5e4;
po=FS(n1);
% Add noise & smooth
rd=rn(n1);
[p,k,s]=SM(po',rd,1);
% Now add storm swirling action
% - This will be done using the cross-product with points scattered on the
% surface
% Storms
xp=randn(3,26);
xp=xp./v(xp);
cpz=[-1,0,0];
xp=[xp,cpz(:),cpz(:)];
% Compute migration vectors
p2=p';
c=1;
for nn = 1:148
pob = p2./v(p2);
for n = 1:size(xp, 2)
if n == 1
xc = XP(xp(:,n),pob);
else
xc = xc + XP(xp(:, n),pob);
end
end
p2 = (p2./v(p2) + xc/1500).*s';
% Store for movement in animation
if nn>50&&mod(nn,2)==0
sn=(s'.*u(v(xc),1,1.5)).^.2;
pn{c}=pob.*sn;
tp=(erf((u(sn)-.5)*10)/2+.5)';
c=c+1;
end
end
% Shorteners
A='AmbientS';
E='EdgeC';
F='FaceC';
D='DiffuseS';
O='none';
S='SpecularS';
G='FaceA';
% Plot clouds
T=trisurf(k,pn{1}(1,:),pn{1}(2,:),pn{1}(3,:),E,O,F,[0.5,0.3,0.3],A,.1,D,1,G,'interp','FaceVertexAlphaD',tp,'AlphaDataM',O); % Plot
hold on;
% % % Now for the planet surface...
rng(6,'twister');
n2=5e3; % Fewer points...
po=FS(n2);
% Same procedure but with different smoothing, compression for ocean values
% etc.
rd=rn(n2);
[~,k,s]=SM(po',rd,2);
s=(u(s)-.6)*10;
s(s<0)=erf(s(s<0));
s=(s+.5)/60+1;
p=po'.*s;
% Plot
trisurf(k,p(:,1),p(:,2),p(:,3),s,E,O,A,0,D,1,S,.2,F,'interp'); % Plot
% Choose a terrain colormap
colormap(hot);
caxis([1,1.1]);
% Add light etc.
axis equal off
set(gcf,'color','k');
b='position';
j=@light;
j(b,[-1,-1,1]);
j(b,[-1,-1,1],'color',[1,1,1]*.5);
% % % Have enough room left for some atmosphere effect. Make a ring around
% planet with gaussian transparency
[xf,yf,zf]=sphere(400);
scl=1.12;
xf=xf*scl;
yf=yf*scl;
zf=zf*scl;
ap=exp(-(u(xf)-.35).^2*150);
T2=surf(xf,yf,zf,'FaceC',[0.1,0,0],E,O,G,'flat','AlphaData',ap,A,.15,D,1,S,0);
V=@(x)hgtransform('Parent',gca);
% Transforms
H=V();
H2=V();
w='parent';
set(T2,w,H);
axis vis3d
s=randn(3,n1);
% Adding some stars in the background
s=9*s./v(s);
l=rand(1,n1);
scatter3(s(1,:),s(2,:),s(3,:),l*100,l'.*[1,1,1],'.',w,H2);
% Camera position etc.
campos([-8,0,0]);
camva(12);
camtarget([0,-.2,0]);
end
% Plot
agc=0:.016:.78;
a=agc(f);
T.Vertices = pn{f}';
campos([-8*cos(a),-8*sin(a),0]);
S=@(x,y)set(x,'Matrix',makehgtform('zrotate',a*y));
S(H,1);
S(H2,.9);
end
% Fibonacci sphere
function s=FS(n)
N=0:n-1;
t=2*pi*N/((1+5^.5)/2);
p=acos(1-2*(N+.5)/n);
s=[cos(t).*sin(p);sin(t).*sin(p);cos(p)];
end
% Flow direction on sphere surface
function cp=XP(n,p)
n=n/vecnorm(n)*.9;
d=sqrt(sum((n - p).^2));
cp=cross(p, n.*ones(1,size(p,2)))./d.^2;
end
% Mesh smoothing
function [p,k,s]=SM(in,rd,r)
n=size(in,1);
k=convhull(in); % Points on "in" must lie on unit circle
c=@(x)sparse(k(:,x)*[1,1,1],k,1,n,n); % Connectivity
t=c(1)|c(2)|c(3); % Connectivity
f=spdiags(-sum(t,2)+1,0,t*1.)*r; % Weighting
s=((speye(n)+f'*f)\rd); % Solve for s w/regularizer
p=in.*s;
end
Animation
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