搞氣氛！用MATLAB畫一棵Bling Bling的圣誕樹

0.前言

馬上圣誕節了，今天推一篇用MATLAB畫圣誕樹的，效果如下圖所示：

1.準備作業

因為這次用的是MATLAB，不像PYTHON一樣需要裝一些依賴庫，要實作本文的效果，只需安裝MATLAB即可，

2.動起手來

2.1 畫樹

要畫圣誕樹，首先...畫棵樹，然后再想辦法來點綴它，

close all;clear;clc
% setup
snow=450;    % number of snow flakes [0 .. 5000]
% 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
h0  = figure('Units','inches');
pos = h0.Position;
pos(1) = 1; pos(2) = 1;
pos(3) = 7; pos(4) = 7;
h0.Position = pos;
surfl(X,Y,Z,'light')

2.2 服道化

下一步，給樹打個光，填個色，角度調整一下來點三維效果，把坐標系顯示去掉，然后一棵綠油油的樹就出現了，

%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('Merry Christmas','color','w',...
    'fontsize',25,...
    'fontweight','Bold')

接下來，把影像底色調一下，用一個五彩斑斕的黑加點星空藍當背景（此處在某甲方選手不斷提出色彩需求后最終確定的顏色，致謝！）

然后再擺幾個小禮物盒子在樹下，這過節氣氛杠杠的，

set(gcf,'color',[22 32 51]./255)
% Presents
%Draw some presents around the tree (each with random color)
drawPresent(2,-4,0,3,3,2);
drawPresent(-4,3,0,2,3,1.5);
drawPresent(5,3,0,4,3,3);
drawPresent(-14,-5,0,6,3,1);
drawPresent(-9,-10,0,2,2,2);
drawPresent(0,4,0,4,3,3);
drawPresent(-6,-13,0,3,3,3);

2.3 雪花飄飄

最后，關鍵部分，撒點雪花，再畫點彩燈到圖上，調整三維影像的角度，來點影片效果，結束戰斗！

% Snow
%create some random 3D coordinates for the snow (amount as in setup above)
snowX=(rand(snow-100,1)*25-12.5);
snowY=(rand(snow-100,1)*25-12.5);
snowZ=(rand(snow-100,1)*27);
color0 = jet(length(snowX));
%Note:Some flakes will end up IN the tree but just can't be seen then
for ii = 1:length(snowX)
    plot3(snowX(ii),snowY(ii),snowZ(ii),'*','color',color0(ii, :),'markersize',randi(15))%plot coordinates as white snow flakes
    %     plot3(snowX(ii),snowY(ii),snowZ(ii),'*','color',color0(ii, :))%plot coordinates as white snow flakes
end
h=plot3(snowX,snowY,snowZ,'w*');
im = {};
for ii = 1:180
    if mod(ii,3) == 0
        h.Visible = 'off';
        snowX=(rand(snow,1)*25-12.5);
        snowY=(rand(snow,1)*25-12.5);
        snowZ=(rand(snow,1)*27);
        h=plot3(snowX,snowY,snowZ,'w*');
        %         pause(0.25)
    else
        view([ii,4])
        %         pause(0.1)
    end
    if ii > 85
        frame = getframe(gcf);
        im{ii} = frame2im(frame);
    end
end
hold off%Done

2.4 輸出gif檔案

此處有知識點！敲黑板！！如何清除cell陣列中的空元素，

im(cellfun(@isempty,im))=[];

file2write = 'chris.gif';
for ii = 1:length(im)
    [A, map] = rgb2ind( im{ii}, 256);
    if ii == 1
        imwrite(A, map, file2write, 'gif','LoopCount',Inf,'DelayTime', 0.12);
    else
        imwrite(A, map, file2write, 'gif','WriteMode','append','DelayTime', 0.12);
    end
end

3.結論

大功告成，

用MATLAB實作一個Bling Bling的圣誕樹，祝大家玩得開心，

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