render_views.m

function ims = render_views( mesh, varargin )
%RENDER_VIEWS render a 3d shape from multiple views
%   mesh::
%       a mesh object containing fileds
%           .F 3 x #faces (1-based indexing)
%           .V 3 x #vertices
%       OR a path to .off file
%   `az`:: (default) [0:30:330]
%       horizontal viewing angles, use this setting for shapes that are
%       upright oriented according to +Z axis!
%   `el`:: (default) 30
%       vertical elevation, , use this setting for shapes that are
%       upright oriented according to +Z axis!
%   `use_dodecahedron_views`:: (default) false
%       ignores az, el -  places cameras on the vertices of a unit
%       dodecahedron, rotates them, and produces 80 views.
%       use this setting for shapes that are not upright oriented.
%   `colorMode`:: (default)  'rgb'
%       color mode of output images ('rgb' or 'gray')
%   `outputSize`::  (default)  224
%       output image size (both dimensions)
%   `minMargin`:: (default)  0.1
%       minimun margin ratio in output images
%   `maxArea`:: (default)  0.3
%       maximun area ratio in output images
%   `figHandle`:: (default) []
%       handle to existing figure

opts.az = [0:30:330];
opts.el = 30;
opts.use_dodecahedron_views = false;
opts.colorMode = 'rgb';
opts.outputSize = 224;
opts.minMargin = 0.1;
opts.maxArea = 0.3;
opts.figHandle = [];
opts = vl_argparse(opts,varargin);

if isempty(opts.figHandle)
    opts.figHandle = figure;
end

if opts.use_dodecahedron_views
    phi = (1+sqrt(5))/2;
    
    vertices = [
        1, 1, 1;
        1, 1, -1;
        1, -1, 1;
        1, -1, -1;
        -1, 1, 1;
        -1, 1, -1;
        -1, -1, 1;
        -1, -1, -1;
        
        0, 1/phi, phi;
        0, 1/phi, -phi;
        0, -1/phi, phi;
        0, -1/phi, -phi;
        
        phi, 0, 1/phi;
        phi, 0, -1/phi;
        -phi, 0, 1/phi;
        -phi, 0, -1/phi;
        
        1/phi, phi, 0;
        -1/phi, phi, 0;
        1/phi, -phi, 0;
        -1/phi, -phi, 0;
        ];
    
    num_vertices = size(vertices,1);
    
    opts.az = zeros(num_vertices, 1);
    opts.el = zeros(num_vertices, 1);
    
    for i=1:num_vertices
        opts.az(i) = (vertices(i,2) / vertices(i,1));
        opts.az(i) = atan(opts.az(i)) / pi * 180 + 180 * (sign(vertices(i,1))==-1);
        
        opts.el(i) = (vertices(i,3) / sqrt(vertices(i,1) * vertices(i,1) + vertices(i,2) * vertices(i,2)));
        opts.el(i) = atan(opts.el(i)) / pi * 180;
    end
end

if ischar(mesh),
    if strcmpi(mesh(end-2:end),'off') || strcmpi(mesh(end-2:end),'obj')
        mesh = loadMesh(mesh);
    else
        error('file type (.%s) not supported.',mesh(end-2:end));
    end
end

if opts.use_dodecahedron_views
    ims = cell(1, length(opts.az) * 4);
    im_counter = 0;
    for i=1:length(opts.az)
        plotMesh(mesh,'solid',opts.az(i),opts.el(i));
        for cv=1:4
            im_counter = im_counter + 1;
			ims{im_counter} = print('-RGBImage', '-r100'); %in case of an error,you have an old matlab version: comment this line and uncomment the following 2 ones
            %saveas(opts.figHandle, '__temp__.png');
            %ims{im_counter} = imread('__temp__.png');
            if strcmpi(opts.colorMode,'gray'), ims{im_counter} = rgb2gray(ims{im_counter}); end
            ims{im_counter} = resize_im(ims{im_counter}, opts.outputSize, opts.minMargin, opts.maxArea);            
            camroll(90);
        end        
    end
else
    ims = cell(1,length(opts.az));
    for i=1:length(opts.az),
        plotMesh(mesh,'solid',opts.az(i),opts.el);
		ims{i} = print('-RGBImage', '-r100');  %in case of an error,you have an old matlab version: comment this line and uncomment the following 2 ones
        %saveas(opts.figHandle, '__temp__.png');
        %ims{i} = imread('__temp__.png');
        if strcmpi(opts.colorMode,'gray'), ims{i} = rgb2gray(ims{i}); end
        ims{i} = resize_im(ims{i}, opts.outputSize, opts.minMargin, opts.maxArea);
    end
end

%delete('__temp__.png');

end




function im = resize_im(im,outputSize,minMargin,maxArea)

max_len = outputSize * (1-minMargin);
max_area = outputSize^2 * maxArea;

nCh = size(im,3);
mask = ~im2bw(im,1-1e-10);
mask = imfill(mask,'holes');
% blank image (all white) is outputed if not object is observed
if isempty(find(mask, 1)),
    im = uint8(255*ones(outputSize,outputSize,nCh));
    return;
end
[ys,xs] = ind2sub(size(mask),find(mask));
y_min = min(ys); y_max = max(ys); h = y_max - y_min + 1;
x_min = min(xs); x_max = max(xs); w = x_max - x_min + 1;
scale = min(max_len/max(h,w), sqrt(max_area/sum(mask(:))));
patch = imresize(im(y_min:y_max,x_min:x_max,:),scale);
[h,w,~] = size(patch);
im = uint8(255*ones(outputSize,outputSize,nCh));
loc_start = floor((outputSize-[h w])/2);
im(loc_start(1)+(0:h-1),loc_start(2)+(0:w-1),:) = patch;

end