Pinning doesn't work for vertical cloth deformation?

Support Particles and Physics Simulations
1

In 2.79, following this tutorial but for a slightly different setup, https://www.youtube.com/watch?v=c11l2o5uCQs

I created a single vertical line (parallel to the global Z axis) mesh with 5 vertices.

Then while in edit mode went to the vertex group panel and created a vertex group,

At the top vertex I set the weight to 1.0 and hit assign,

At the next vertex I selected it, set the weight to 0.5 and hit assign,

At the next vertex I selected it, set the weight to 0.33 and then hit assign and so on.

Now when I go to the cloth physics editor and assign this mesh cloth physics and then I select that vertex group for the pinning and then hit the play button in the timeline, nothing happens, it doesn’t droop down as it should. Does cloth physics somehow have no effect on vertical stretching? If I deselect the pinning option then the entire mesh falls to -infinity, so I know I weighted all the vertices, and double checked in edit mode with the ctrl+N panel to verify they all have the correct weights.

2

As it’s vertical, the cloth (string) might be starting in a stable state. Try rotating it so it’s not parallel to the z axis.

set the weight to 0.33 and then hit assign and so on.

Also, are all the vertices pinned or are some free.

3

It does droop when I rotate the mesh, but then the problem is the mesh is rotated, it’s not realistic because it looks like there’s some magical extra force holding it up for no reason.

How do I get what’s happening in the video to also work in the vertical direction? Do I have to use both cloth and soft body? But then if I use soft body how do I restrict the vertical deformation to only the global z axis? And is there a way to set blender’s global gravity so that it’s -9.8m/s^2?

4

Blenders gravity is set to -9.8m/s^2. See ‘Properties Window’->‘Scene Properties tab’->Gravity.

I’m not fully sure what you’re after. The video show a hat that reacts nicely when it’s moved around. I’m thinking you’re after a string that reacts nicely when it’s moved around. Have you tried animating the object to move it around.

5

Vertical. Vertical vertical vertical vertical vertical,
vertical
is the key word here.

Realistically, a flexible object will sag down under its own weight. If I hold a vertical line segment (parallel to the global Z axis), it should sag down on its own too, without rotating it at all by any amount. However, for some reason cloth physics does not make this vertical sag happen, even though it can calculate it at other angles.

6

The cloth has a tension property (cloth->‘physical properties’->stiffness->tension. Try changing it to 0.1 .

7

That sounds promising but unfortunately I don’t see it. Are you sure it’s an option available for 2.79?

When I try and find that panel under for 2.79 in the documentation I get this https://docs.blender.org/manual/en/2.79/physics/cloth/settings/physical_properties.html

so you must be using a later version.

8

I’m using version 2.80

I think this is 2.79:

Structural is the property you need to play with. (Ignore the highlighted area, it came with the image from the internet.)

9

Alright thank you, it looks like that does allow sagging when I move the value to near 0, and the velocity seems to control how fast is slows down, though I don’t know which velocity setting corresponds to a more spring-like object falling.