# How to plot two moving robot in the same figure and change one of them transparency？

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snow John on 22 Sep 2022
Commented: snow John on 5 Oct 2022
Hello guys ，i want plot two moving robot in the the figure and change on of them transparency.
but i don't know how to change just on of them transparency use the code
alpha(robot,0.2) %change robot transparency
and i just want to implement the effect like below
And i try to use the task and joint space trajectory example to implement the result
The code are below for the purpose change
axis([-.8 .8 -.8 .8 0 1.2]);
view(135,15)
for i=1:length(trajTimes)
% Current time
tNow= trajTimes(i);
% Interpolate simulated joint positions to get configuration at current time
configNow = interp1(tJoint,stateJoint(:,1:numJoints),tNow);
configNow1 = interp1(tJoint,stateJoint(:,1:numJoints),tNow+1);
poseNow = getTransform(robot,configNow,endEffector);
show(robot,configNow1,'PreservePlot',false,'Frames','off');
hold on
show(robot,configNow,'PreservePlot',false,'Frames','off');
jointSpaceMarker = plot3(poseNow(1,4),poseNow(2,4),poseNow(3,4),'r.-','MarkerSize',2);
% alpha(robot,0.2)% here didn't works
alpha 0.2
drawnow limitrate ;
end
but only one moveing like below picture shows
Can someone help me
Best wishes，
-jian

Karsh Tharyani on 4 Oct 2022
Hi Jian,
I hope this snippet helps.
% Create two instances of a rigid body tree since we want two visuals
copyrbt=copy(rbt);
% Some random configurations
q0=homeConfiguration(rbt);
q1=randomConfiguration(rbt);
q2=randomConfiguration(rbt);
% Generate a trajectory to the random configurations
tpts=[0,1];
tquery=tpts(1):0.01:tpts(end);
traj1=quinticpolytraj([q0',q1'],tpts,tquery)';
traj2=quinticpolytraj([q0',q2'],tpts,tquery)';
% Find the patches which have a display name of '_mesh', and set their
% alpha values.
ax=show(rbt,traj1(1,:),PreservePlot=false,FastUpdate=true);
rbtpatches=findobj(ax.Children,'Type','patch','-regexp','DisplayName','_mesh');
set(rbtpatches,'FaceAlpha',0.2);
% Now visualize another instance of the same robot
hold on;
show(copyrbt,traj2(1,:),PreservePlot=false,FastUpdate=true,Parent=ax);
% This call will also find the previous patches. Hence we need to remove
% previously found patches from this query.
patchesnew=findobj(ax.Children,'Type','patch','-regexp','DisplayName','_mesh');
copyrbtpatches=patchesnew(~ismember(patchesnew,rbtpatches));
% You can also change the color aside from alpha
set(copyrbtpatches,'FaceAlpha',0.7);
set(copyrbtpatches,'FaceColor',[1,0,0]);
%% Visualize
rc=rateControl(50);
for i=1:size(tquery,2)
show(rbt,traj1(i,:),PreservePlot=false,FastUpdate=true);
show(copyrbt,traj2(i,:),PreservePlot=false,FastUpdate=true,Parent=ax);
waitfor(rc);
end
hold off;
Best,
Karsh
snow John on 5 Oct 2022
Hi Karsh，
Thanks very much for your kindness help ，The source code are really help a lot. I do want to implement these kind of result，this kinds of visualization is very attractive for representation use.
Thanks agian
Best ,
-Jian

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