Efficient data storage for real-time simulation
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I am currently working on a real-time simulation using MATLAB and MEX-files. I have a triangulated mesh of ~2000 vertices and ~4000 faces stored in two matrices v (Nx3, N:number of vertices and 3-dimensions) and f. I am using a mass-spring model to simulate deformations, for which I am constantly pulling and inserting data from the vertex matrix v to calculate displacements, distances, spring-forces etc. The reason why I am storing in Nx3 format is to be able to plot using trisurf(f,v(:,1), v(:,2), v(:,3)).
I am currently not reaching my target updates of 20 iterations/sec (currently around ~11 iterations/sec) and the profiler does not really target any specific area in the code for improvement. I am wondering if maybe a different approach to store the vertices may be more efficient? E.g. storing the vertices in a 3*Nx1 long vector instead. This would not make it suitable for trisurf though. Thoughts or comments?
Current version, pseudo-code:
for t=1:T
for i = 1:N
%Pull vertex i
xi = v(i,:); %xi = [x_i y_i z_i]
for k = 1:numConn(i) %number of connections numConn(i) is precomputed
%Pull a vertex
j=connection(k,i); %j equals a row in v, i.e a vertex
xj=v(j,:);
%Distance
xij=xi-xj;
d = sqrt(xij*xij');
end
...
%Update
v(i,:)=v(i,)+f(d,xi,vj,t);
end
%Plot
trisurf(f,v(:,1),v(:,2),v(:,3));
drawnow;
end
4 个评论
Wouter
2013-3-21
If you have the parallel processing toolbox, you could perhaps try to make the code run parallel on all you processors; this could theoretically speed up the execution (if processing power is actually the limiting factor).
If you are lucky, you could change the inner for loop into this:
parfor k = 1:numConn(i)
however I suspect that your iterations depend on previous iterations (line v(i,:) = v(i,:)+f(d,xi,vj,t). In that case ignore my comment :)
采纳的回答
Wouter
2013-3-20
You could try to update these lines:
trisurf(f,v(:,1),v(:,2),v(:,3));
drawnow;
Into:
if ~exist('htri','var')
htri = trisurf(f,v(:,1),v(:,2),v(:,3));
else
set(htri,'vertices',v); % use if faces (f) do not change
% set(htri,'vertices',v,'faces',f); % use if both vertices
% % and faces change
end
drawnow
This might be faster as you then do not run the entire trisurf function again.
6 个评论
Wouter
2013-3-20
If the connections between the vertices remain the same you could try to find the connected vertices before the for-loops (e.g. using the ismember function) and then use these in the for loop in stead of calculating them each iteration.
Another option would be to vectorize you innermost for-loop (for i = 1:N). If this can be done depends however on the fact that subsequent iterations do not depend on each other.
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