# Dynamic Relaxing Method and Force Density Method

Hello Friends
I wanted to find an optimal form
What is the difference between Dynamic Relaxing Method and Force Density Method?
I saw some educational videos in Kangaroo 2 plugin, but I did not understand the difference between these two methods.
Thanks.

Force density method works on link or cable elements where the ratio F/L defined as the force density is assigned. Equilibrium equations on the nodes are solved and a net in equilibrium with all links in tension is the result.(F =final tension L=final length)

Dynamic relaxation instead of a force density we assign a initial pre stress to the links and equilibrium is searched using dynamic equilibrium equations of motion with fictions masses and damping.

Both methods have been extended to surface (triangles and quad elements) to solve for surface in equilibrium under predefined warp-weft pre stress field.

Kangaroo I think is a variation of the dynamic method where more features are available.

Gd

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If you set the initial length to zero in Kangaroo, then the strength becomes the force density. If your model has only cables with initial lengths zero, then both methods solve exactly the same equation, return the same solution.

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This paper provides a terse overview and comparison:

I’ve found this book to be a terrific resource for understanding and comparing the various form finding methods in greater detail and with practical examples:

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