makeTree.m

% Modified from a plot by 
% Anselm Ivanovas<anselm.ivanovas@student.unisg.ch>
% URL: http://www.mathworks.com/matlabcentral/fileexchange/22478-a-christmas-tree-plot
% Copyright (c) 2008, Anselm
% All rights reserved.

function [X,Y,Z] = makeTree
%% draw tree
h=0:0.2:25; %vertical grid
[X,Y,Z] = cylinder(tree(h)); %produce a tree formed cylinder
Z=Z*25; %scale to the right heigth

%Add some diffusion to the surface of the tree to make it look more real

treeDiffusion=rand(126,21)-0.5;%some horizontal diffusion data

%add diffusion to the grid points 
for cnt1=1:21
    
    for cnt2=16:126%starting above the trunk
        %get the angle to always diffuse in direction of the radius
        angle=atan(Y(cnt2,cnt1)/X(cnt2,cnt1));
        %split the diffusion in the two coordinates, depending on the angle
        X(cnt2,cnt1)=X(cnt2,cnt1)+cos(angle)*treeDiffusion(cnt2,cnt1);
        Y(cnt2,cnt1)=Y(cnt2,cnt1)+sin(angle)*treeDiffusion(cnt2,cnt1);
        %some Vertical diffusion for each point
        Z(cnt2,cnt1)=Z(cnt2,cnt1)+(rand-0.5)*0.5;
    end
    
end
%draw the tree
surfl(X,Y,Z,'light')

%% View and format

%Use as nice green color map (darker at the bottom, lighter at the top)
r=(0.0430:(0.2061/50):0.2491)';%red component
g=(0.2969:(0.4012/50):0.6981)';%green component
b=(0.0625:(0.2696/50):0.3321)';%blue component
map=[r,g,b];%join in a map
for cnt=1:6
    %change the lower part to brown for the trunk
    map(cnt,:)=[77,63,5]/265;
end

colormap(map)%set the map
view([-37.5,4])%Change the view to see a little more of the Actual 3D tree
lighting phong %some nice lighting
shading interp %remove grid and smoothen the surface color
axis equal %takes care of display in the right proportion
axis([-10 10 -10 10 0 30]) %give some more axis space (for the snow later)
% axis off %but don't show axis
hold on %to draw the rest
title('Ornaments Placement')%self explaining

end % of function


%% ============= private functions

function r=tree(h)%Gives a profile for the tree
for cnt=1:length(h)
    
    if(h(cnt)==0)%no Width at the bottom. Ensures a "closed" trunk
        r(cnt)=0;
    end
    %smaller radius for the trunk
    if (h(cnt)>0 && h(cnt)<=3)
        r(cnt)=1.5;
    end

    %reduce radius gradually from 8 to 0. Note: will only work with a trunk heigth
    %of 3 and a whole tree heigth of 25. Scale the height of the tree in
    %the "draw tree" section, since the cylinder command will return a 1
    %unit high cylinder anyway
    if(h(cnt)>3)
        r(cnt)=8-(h(cnt)-3)*0.3636;
    end

end

end % of function