Help [Question] Does the Cross-sectional area of rope change?

[YashJ]

Hi, I have very recently started using Unity physics engine for a research problem. I need to calculate the contact area between two ropes when they are being twisted together. I feel that Obi Rope should be able to bend and change it's cross-sectional area for me to be able to calculate it but I was't sure. Can I define the parameters for the elasticity of the rope in it's cross-section? Will the cross-sectional area change with force applied?

[josemendez]

Hi, I have very recently started using Unity physics engine for a research problem. I need to calculate the contact area between two ropes when they are being twisted together. I feel that Obi Rope should be able to bend and change it's cross-sectional area for me to be able to calculate it but I was't sure. Can I define the parameters for the elasticity of the rope in it's cross-section? Will the cross-sectional area change with force applied?

Hi,

Under no circumstance will cross section of the rope change. Rope is modeled as a linear chain of distance constraints between massive elements (particles), for the cross section to deform due to forces a volumetric approach like tetrahedral FEM would be needed, which is much more expensive.

Imho using a particle-based engine to calculate contact areas is a really bad idea, mainly because the contact manifold area between two spherical particles is guaranteed to always be zero (a single point). You won't be able to extract any meaningful contact area information from it. You could have a very rough approximation : the amount of contacts between the two ropes, scaling each one by the area of the spurious intersection circle between the particle pair (which should always be very close to zero, anyway)…

You can read more about how the simulation works here:
http://obi.virtualmethodstudio.com/tutor...gence.html