Tracing the Trajectory of a Circle of radius R around the line plot of position

I am working on some plots between interacting micro-swimmers in a 2D fluid which are modelled as circles. I have my code to output the positions of the swimmers as they swim and interact. However, because they have a radius R I want to trace the path of the whole circle as it moves to check that the spheres don't collide as my model doesn't account for this.

Below I have an example of a plot of two interacting swimmers that deflect each other due to their flow/turbulance as they progress through the fluid. I would like each line to be exactly of thickness 1 (i.e Radius = 0.5). Changing the line thickness directly on the plot doesn't work as it does not scale with the magnification/axes scale. What would be good is keeping the original line but with a slightly transparent or lighter colour trace of a circle of radius R moving along this line.

Hope this makes sense,

Cheers

[Dyuman Joshi]

You can draw a parallel lines to the original curve, one above the curve and one below the curve, with a specified distance.

Answer 1

[Shushant]

Hi William,

I understand that while plotting a line you want it to be of certain thickness, which is not affected by the change in scale. To achieve this you can use "polyshape".

For example, Plotting a line from (-5,0) to (0,60) with thickness 1.

pgon = polyshape([-5 -5 0 0], [0.5 -0.5 59.5 60.5]);
plot(pgon)

Refer to the following documentation for more information -

2-D polygonal shapes - MATLAB - MathWorks India

I hope this helped in solving the issue you were facing.

Thank you,

Shushant

[Dyuman Joshi]

That would be rather difficult and/or messy for curves with bends, which is what OP is working with.