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+--- Thread: Help Difficulty with rope and forces when attached to cloth (/thread-3638.html)
Difficulty with rope and forces when attached to cloth - MEPETAMINALS - 09-11-2022
Essentially what I'm trying to do here:
I have an Obi cloth object (the sail)
The sail has two particle groups, one connected to the mast spar via a static particle attachment point. The second connects to the sphere via a dynamic particle attachment.
The idea is to be able to attach a rope to the sphere as well, and manipulate in a variety of ways. However, when I attach an obi rope to the sphere in the same method -- it seems to be radically more affected by the ambient force in the scene -- enough to stretch the sail in its effort to fly away. Increasing the mass of the rope (or the sphere) has minimal effect.
Can you give me some feedback as to what is going on here? My intent/expectation was for the rope to hang from the sphere in a similar manner to the sphere alone.
I've included two images. The first is the sail + sphere without the rope. The second shows the same scene after activating the rope.
In an effort to minimize variables, collisions have been disabled for all obi colliders. Both the rope and sail use the same solver.
[attachment=1534]
[attachment=1535]
RE: Difficulty with rope and forces when attached to cloth - josemendez - 09-11-2022
(09-11-2022, 02:55 PM)MEPETAMINALS Wrote: Essentially what I'm trying to do here:
I have an Obi cloth object (the sail)
The sail has two particle groups, one connected to the mast spar via a static particle attachment point. The second connects to the sphere via a dynamic particle attachment.
The idea is to be able to attach a rope to the sphere as well, and manipulate in a variety of ways. However, when I attach an obi rope to the sphere in the same method -- it seems to be radically more affected by the ambient force in the scene -- enough to stretch the sail in its effort to fly away. Increasing the mass of the rope (or the sphere) has minimal effect.
Can you give me some feedback as to what is going on here? My intent/expectation was for the rope to hang from the sphere in a similar manner to the sphere alone.
Hi!
Force zones have a special consideration for cloth (and fluids): they're considered wind sources, and aerodynamic constraints are used. The strength of the wind force is modulated by the aerodynamic constraint's drag and lift parameters, which take into account the shape of the cloth and its orientation relative to the wind direction, in addition to its mass. For instance, this drag/lift model is what allows flags to undulate instead of simply stretching straight in the direction of the wind.
Ropes however do not use a specific aerodynamic model, so they do not have any aerodynamic parameters unlike cloth and their reaction to external forces only depends on mass.
In practice: try increasing the drag and lift coefficients of your cloth until it reacts in a way similar to the rope, then lower the force zone strength until both ropes and cloth behave the way you want.
RE: Difficulty with rope and forces when attached to cloth - MEPETAMINALS - 09-11-2022
(09-11-2022, 03:25 PM)josemendez Wrote: Hi!
Force zones have a special consideration for cloth (and fluids): they're considered wind sources, and aerodynamic constraints are used. The strength of the wind force is modulated by the aerodynamic constraint's drag and lift parameters, which take into account the shape of the cloth and its orientation relative to the wind direction, in addition to its mass. For instance, this drag/lift model is what allows flags to undulate instead of simply stretching straight in the direction of the wind.
Ropes however do not use a specific aerodynamic model, so they do not have any aerodynamic parameters unlike cloth and their reaction to external forces only depends on mass.
In practice: try increasing the drag and lift coefficients of your cloth until it reacts in a way similar to the rope, then lower the force zone strength until both ropes and cloth behave the way you want.
Interesting. Thank you for the response, that makes sense.