dForce: keep the bending object's shape

feldarzt

How can I keep an object's shape while it's bending? Like it's a garden hose or an optic cable?

rosseliani

Export it as an.obj file, then use Morph loader Pro to retrieve the shape.Set the new morph at 100%, Erc freeze (edit mode), save as morph asset.

Richard Haseltine

If you want to stop it from collapsing into a ribbon while still bening the answer is a dForce AddOn - e.g. a series of squares with corners that exactly coincide with the vertices of your tube. When simulating dForce will track those collisions, but otherwise will not interact with the AddOn, so it can act as a stiffener without otherwise affecting the simulation. Mada has a video on this.

feldarzt

Thanks for the idea!
However, I failed to mention (actually, didn't think it would matter) that I'm making a scene with animation, so a single morph solution won't really work. But it's definitely a good idea for a single-frame render.

rosseliani said:

Export it as an.obj file, then use Morph loader Pro to retrieve the shape.Set the new morph at 100%, Erc freeze (edit mode), save as morph asset.

feldarzt

Richard, you're a life saver, as usual! For those who'll look for the solution in the future, here's the video:

Richard Haseltine said:

If you want to stop it from collapsing into a ribbon while still bening the answer is a dForce AddOn - e.g. a series of squares with corners that exactly coincide with the vertices of your tube. When simulating dForce will track those collisions, but otherwise will not interact with the AddOn, so it can act as a stiffener without otherwise affecting the simulation. Mada has a video on this.

feldarzt

But it seems like in some cases/frames this doesn't work as expected. Like that Dynamic Addon isn't strong enough to support the weight/force of the object.

Maybe there are more options for keeping the object's shape?

Mada

I don't do a lot of animation so I'm not sure how far you can push it. For a cable you'd need a lot of geometry to keep it from collapsing. I did something similar on the Gorgon Tail so it can be simulated flat against a surface. I ended up with 2 add ons. One to support the main shape, and then another set to support the sides because they were collapsing a bit more than I liked during a sim. Combining both into 1 geometry didn't work as well, I got better results by splitting them into 2.

First image shows the tail with the internal shapes in wireframe

2nd image is the first addon

3rd image is the second addon to support the sides

4th image is after a sim where it dropped down lower on a plane

 

feldarzt

Looks like I made my support addon slightly wrong. Thanks so much for the pics, they are super informative!

Also, is it really important for the faces in the addon to be bridge? Won’t “regular” faces (like the ones Blender adds by the Fill command) work as much as bridges?

 

Mada said:

I don't do a lot of animation so I'm not sure how far you can push it. For a cable you'd need a lot of geometry to keep it from collapsing. I did something similar on the Gorgon Tail so it can be simulated flat against a surface. I ended up with 2 add ons. One to support the main shape, and then another set to support the sides because they were collapsing a bit more than I liked during a sim. Combining both into 1 geometry didn't work as well, I got better results by splitting them into 2.

First image shows the tail with the internal shapes in wireframe

2nd image is the first addon

3rd image is the second addon to support the sides

4th image is after a sim where it dropped down lower on a plane

 

Mada

feldarzt said:

Looks like I made my support addon slightly wrong. Thanks so much for the pics, they are super informative!

Also, is it really important for the faces in the addon to be bridge? Won’t “regular” faces (like the ones Blender adds by the Fill command) work as much as bridges?

I don't think it matters how you make them, as long as the vertices stays put where it connects to the main mesh. The slightest shift will cause the add on to not connect. Only way is to make it and experiment till you get the best option :)

feldarzt

I’m using the same .obj for both the object and the addon, cutting the (seemingly) unnecessary parts for the latter, so the vertices are probably in the same places.
Currently, I think I made the addon as it should be, as a set of broadwise “walls” along the “cable.” But the “cable” explodes as soon as I start the simulation. I know that for clothing and such items, a (mostly) working solution is to increase the space between the clothing and the figure, but in this case, it obviously is not an option. Have you encountered such behavior during your work on that tail?


UPD: Maybe I'm doing something wrong with the addon property because as long as I list the addon itself as a dynamic surface, the simulation per se is going okay. But the object is crumbling, although not totally. Oh, dForce, mysterious thine ways art!
 

Mada said:

feldarzt said:

Looks like I made my support addon slightly wrong. Thanks so much for the pics, they are super informative!

Also, is it really important for the faces in the addon to be bridge? Won’t “regular” faces (like the ones Blender adds by the Fill command) work as much as bridges?

I don't think it matters how you make them, as long as the vertices stays put where it connects to the main mesh. The slightest shift will cause the add on to not connect. Only way is to make it and experiment till you get the best option :)

crosswind

@mada

I ever learnt Dynamic Surface Add-on just from you. But this time the usage of add-on in Gorgon Tail is superbly awesome! I can't wait to experiment. Many thanks!!!

@feldarzt

BTW, if the object you use is a dForce item, Dynamic Surface Add-on would be the best choice in terms of result, though there'll be more workload. If you just use a simple object for bending, you may utilize the technique of JCMs... like Jay's 'Magic Tube', in his tutorial: https://www.youtube.com/watch?v=G4bpd_xgjWU&t=290s

Mada

feldarzt said:

I’m using the same .obj for both the object and the addon, cutting the (seemingly) unnecessary parts for the latter, so the vertices are probably in the same places.
Currently, I think I made the addon as it should be, as a set of broadwise “walls” along the “cable.” But the “cable” explodes as soon as I start the simulation. I know that for clothing and such items, a (mostly) working solution is to increase the space between the clothing and the figure, but in this case, it obviously is not an option. Have you encountered such behavior during your work on that tail?


UPD: Maybe I'm doing something wrong with the addon property because as long as I list the addon itself as a dynamic surface, the simulation per se is going okay. But the object is crumbling, although not totally. Oh, dForce, mysterious thine ways art

Double checking that you're setting the add as an add on? Image attached

I had exploding too when I made the add on too complex and detailed... changing over to 2 add ons each supporting just one direction helped for that. Adjusting your dforce settings will also help with explosions - its hard to say without seeing your mesh. 

 

Mada

This is the sim settings I have for the gorgon tail. Keep in mind that a lot depends on your mesh density. I tend to work in lower polygons, and then use subdivision in DS to up the resolution.

Richard Haseltine

Using the same mesh for the add-on as for the base probably won't work - the idea is to add some bracing, which the original probably won't do or it wouldn't need bracing.

feldarzt

Looks like I misspoke a little. I’m using the original mesh as a base for making the addon, i.e. I’m cutting the addon parts from it. Kinda making sure that the vertices of what’s left are the same vertices that the full mesh has.

Thanks a lot to both you and @mada! After a few iterations of the addon and dForce parameters, I think I have finally achieved the wanted result. Now I only have to figure how to “soften” the dForce reaction to a rapid coordinates change from 0 to 300 at one of my frames, but that’s definitely another story.
 

Richard Haseltine said:

Using the same mesh for the add-on as for the base probably won't work - the idea is to add some bracing, which the original probably won't do or it wouldn't need bracing.