stfeatures_demo.m

cuboid democuboid democuboid democuboid demo

% Demo of stfeatures on the "oscillating example".
%
% From Laptev & Lindeberg papers.
%
% INPUTS
%   periodic    - if 1 uses periodic detector else uses harris detector

function stfeatures_demo( periodic )

    %%% SETTABLE PARAMETERS
    sigma = 1; % a good range appears to be [.2,1.5]?
    tau = 2.5; 
    thresh = .2; maxn = 50; 
    show = 1;

    %%% get parameters for mesh (width must be ints!)
    xstart = .5; xend = 2.2; xstep = .02;
    xwidth = round( (xend-xstart) / xstep )+1;
    tstart = .8; tend = 1.9; tstep = .02;
    twidth = round( (tend-tstart) / tstep )+1;
    ystart = -3; yend = 3; ystep = 1/30; 
    ywidth = round( (yend-ystart) / ystep )+1;
    
    %%% create images
    [X,Y] = meshgrid( xstart:xstep:xend, ystart:ystep:yend );
    sinX4 = sin(X.^4);   tvec = tstart:tstep:tend;
    I = zeros( ywidth, xwidth, twidth );
    for i=1:length(tvec);
        t = tvec(i);
        Z = -sign( Y - sinX4 * sin(t^4) );
        I(:,:,i) = Z;
    end
    
    %%% run harris corner detector
    [R,subs,vals] = stfeatures( I, sigma, tau, periodic, thresh, maxn, [],[],[], show );
    nfeatures = size(subs,1)

    %%% create and dipslay surface mesh with detected interest points

    % create surface mesh
    [X,T] = meshgrid( xstart:xstep:xend, tstart:tstep:tend );
    Y = sin( X.^4 ) .* sin( T.^4 );
        
    % transform X,Y,T to have correct coordinates
    Y = (Y - ystart) ./ ystep +1;  %rows
    X = (X - xstart) ./ xstep +1;  %cols
    T = (T - tstart) ./ tstep +1;  %time
        
    % display surface mesh
    figure(show+4); clf;
    surf(X,T,Y,'FaceColor','red','EdgeColor','none');
    set(gca,'YDir','reverse'); set(gca,'ZDir','reverse'); 
    camlight left; lighting phong; %lighting Gouraud;
    xlabel('col'); ylabel('time'); zlabel('row');
    view(-15,55);
        
    % plot detected interest points on top of mesh
    hold('on');
    for i=1:nfeatures
        ellipsoid( subs(i,2), subs(i,3), subs(i,1), 2.5*sigma, 2.5*tau, 2.5*sigma, 8 );
    end
    hold('off');