Ball trapped inside a car

I have a car moving forward and i ned to trap a ball inside it.

x_casa = [2,12,12,7,2];
y_casa = [1,1,10,14,10];             %obiectul casa
casa = hgtransform;
patch('XData',x_casa,'YData',y_casa,'FaceColor','white','Parent',casa) 
x_drum=[2,2 , 100 , 100 ];
y_drum=[1, 1.2 , 1.2 ,1];                 %obiectul drum
drum = hgtransform;
patch('XData',x_drum,'YData',y_drum,'FaceColor','black','Parent',drum)
roata_spate = hgtransform;                %back wheel
theta = 0:0.1:2*pi;
rad=0.3;
xCent = 13.5;
yCent = 1.3;
xCoord = xCent+rad*cos(theta);
yCoord = yCent+rad*sin(theta);
patch('XData',xCoord,'YData',yCoord,'FaceColor','blue','Parent',roata_spate)
roata_fata = hgtransform;                     %front wheel
theta = 0:0.1:2*pi;
rad=0.3;
xCent2 = 16;
yCent2 = 1.3;
xCoord2 = xCent2+rad*cos(theta);
yCoord2 = yCent2+rad*sin(theta);
patch('XData',xCoord2,'YData',yCoord2,'FaceColor','blue','Parent',roata_fata)
x_sasiu = [12.5, 17.5, 17.5, 15.5, 12.5, 12.3];            % car chassis
y_sasiu = [1.6, 1.6, 3, 4  , 4  , 1.6];
sasiu = hgtransform;
patch('XData',x_sasiu,'YData',y_sasiu,'FaceColor','white','Parent',sasiu) 
ball = hgtransform;                            %ball 
theta = 0:0.1:2*pi;
rad=1;
xCent3 = 15;
yCent3 = 2.7;
xCoord3 = xCent3+rad*cos(theta);
yCoord3 = yCent3+rad*sin(theta);
patch('XData',xCoord3,'YData',yCoord3,'FaceColor','red','Parent',ball)
axis equal     
xlim([0 100])                                                                
ylim([0 30])
pt1 = [0 0 0];
pt2 = [80 0 0];
for t=linspace(0,1,2500)                                    %making the car moving forward
    sasiu.Matrix = makehgtform('translate',pt1 + t*(pt2-pt1));
    roata_fata.Matrix = makehgtform('translate',pt1 + t*(pt2-pt1));
    roata_spate.Matrix = makehgtform('translate',pt1 + t*(pt2-pt1));
    drawnow
end

[Walter Roberson]

Okay, what is your question?

[Walter Roberson]

Instead of having the ball have independent coordinates, parent it to the car, so that when the car moves it automatically moves as well. The coordinates of the ball at any time should be the position of the ball relative to some reference point inside the car.

It is legal to have one hgtransform be parented to another.

[Robert Mirea]

and how shoul i do independent coordinates for the car ? i am pretty new to the coding an i don't know how to do that.

Answer 1

[VINAYAK LUHA]

Hi Robert Mirea,

It is my understanding that you would like to have the ball trapped inside the car such that it moves along with the latter.

Here’s a workaround in which the ball.matrix transformation is updated using the same translation transformation applied to the car chassis. This ensures that the ball remains trapped inside the car as it moves forward. I’ve also updated the “yCoord3” variable such that the ball fits inside the car.

Here’s the modified code for your reference-

x_casa = [2,12,12,7,2];
y_casa = [1,1,10,14,10];             %obiectul casa
casa = hgtransform;
patch('XData',x_casa,'YData',y_casa,'FaceColor','white','Parent',casa) 
x_drum=[2,2 , 100 , 100 ];
y_drum=[1, 1.2 , 1.2 ,1];                 %obiectul drum
drum = hgtransform;
patch('XData',x_drum,'YData',y_drum,'FaceColor','black','Parent',drum)
roata_spate = hgtransform;                %back wheel
theta = 0:0.1:2*pi;
rad=0.3;
xCent = 13.5;
yCent = 1.3;
xCoord = xCent+rad*cos(theta);
yCoord = yCent+rad*sin(theta);
patch('XData',xCoord,'YData',yCoord,'FaceColor','blue','Parent',roata_spate)
roata_fata = hgtransform;                     %front wheel
theta = 0:0.1:2*pi;
rad=0.3;
xCent2 = 16;
yCent2 = 1.3;
xCoord2 = xCent2+rad*cos(theta);
yCoord2 = yCent2+rad*sin(theta);
patch('XData',xCoord2,'YData',yCoord2,'FaceColor','blue','Parent',roata_fata)
x_sasiu = [12.5, 17.5, 17.5, 15.5, 12.5, 12.3];            % car chassis
y_sasiu = [1.6, 1.6, 3, 4  , 4  , 1.6];
sasiu = hgtransform;
patch('XData',x_sasiu,'YData',y_sasiu,'FaceColor','white','Parent',sasiu) 
ball = hgtransform;                            %ball 
theta = 0:0.1:2*pi;
rad=1;
xCent3 = 15;
yCent3 = 2.7;
xCoord3 = xCent3+rad*cos(theta);
yCoord3 = yCent3+rad*sin(theta);
patch('XData',xCoord3,'YData',yCoord3-2.5,'FaceColor','red','Parent',ball)
axis equal     
xlim([0 100])                                                                
ylim([0 30])
pt1 = [0 0 0];
pt2 = [80 0 0];
for t=linspace(0,1,2500)                                    %making the car moving forward
    sasiu.Matrix = makehgtform('translate',pt1 + t*(pt2-pt1));
    roata_fata.Matrix = makehgtform('translate',pt1 + t*(pt2-pt1));
    roata_spate.Matrix = makehgtform('translate',pt1 + t*(pt2-pt1));

    %%Update the position of the ball relative to the car
    ball.Matrix = makehgtform('translate',[pt1(1) + t*(pt2(1)-pt1(1)), yCent3, 0]);
    drawnow
end

Regards

Vinayak Luha