I was wondering how to apply cloth physics to this cape vertex group. I do not need cloth physics on the rest of the mesh. The cape is apart of the mesh and is not separate. Any help is appreciated.

Updated: The main goal of the wind simulation is to test the cloth simulation of the cape. I have done both a cloth simulation, which yielded no results when baked with the wind, and a soft body simulation, which pushed the non-pinned cape away from the model but did not have the cape react as a cloth, just as a stiff object that translated across the view port. I feel like I am missing something more fundamental to this process, but I'm not sure what it is.

enter image description here

  • $\begingroup$ Hey there and welcome. As far as i can see in the vertex group list, you already have a group for the cape. If you create the inverted version of that or have one that essentially is the inverse of the cape, use that as pin group. $\endgroup$ – Xylvier May 8 '20 at 1:43
  • $\begingroup$ By inverted version, do you mean a vertex group that is weight painted all red except for the cape? Then do I pin it in the cloth simulation section "Shape" or soft body simulation section "Goal". I hear they give similar results. $\endgroup$ – John May 8 '20 at 17:06
  • $\begingroup$ Yes, as the cape vertex group is having the cape weighted as 1(red) if used as pin group the cape would not move, as it would be pinned. The pin-group will freeze the red or value 1 in place, values from 1-0 are gradually more affected. Inverted you get a red body, thus pinned/ignored by the cloth effect and the cape can freely flutter/drape or get sucked in a turbine :p. I'd leave softbody simulation for other things like a ball or pillow, but you are most certainly free to try. Though a cape is cloth after all. $\endgroup$ – Xylvier May 8 '20 at 19:16
  • $\begingroup$ Hey thanks for your help! Okay so I made an inverted weight paint of the model with everything red except for the cape. I enabled collision and cloth on the mesh, with the inverted vertex group pinned under the "Shape" section. I added in a wind object in front of the model. When I bake, however, nothing changes and I don't see any simulation. I've been looking through various tutorials, but I'm not sure what I'm missing. Any pointers? $\endgroup$ – John May 8 '20 at 23:00
  • $\begingroup$ I would recommend to update/adjust your question with the end-goal of using wind to affect the cape. Add the new details in the question by using the edit function. I should have some time later to write an answer based on the mentioned details. $\endgroup$ – Xylvier May 9 '20 at 1:08

The entire object, was in triangles which also were separated. A cloth simulation with this would never work to start with, neither would a soft-body simulation. Both are based on a interconnected structure/mesh.

Learning something new along the way, this is what i got, i hope it's somewhat close to your goal.
enter image description here

Now regarding what is needed to get there, or at least to a cape that simulates like cloth:

enter image description here

  1. Since the entire object came triangulated and with all faces separate, we need to select the object, go in edit mode with Tab and select all vertices with A first.
  2. Now we can make the object a whole mesh by pressing Alt+N (Merge) -> By Distance
    enter image description here
  3. Now the object can be separated into the two main parts, body and cape. For that we hover over a part of the cape and press L which will Select Linked vertices, thus the cape and the shoulder-part of it will be selected.
    enter image description here
  4. To really separate the mesh into two objects we need to press P(Separate) and choose Selection. It will create a new object with the selected part.
    enter image description here
    conveniently renamed the objects "body" and "cape"
  5. The separated objects allow for a much cleaner simulation, as the bigger the mesh simulated, the more calculations needed, but we are not yet done.
  6. The cape can further be split in two parts, namely the shoulder-part and the cape itself. I'd recommend to hide(if not mentioned, hiding per outliner eye symbol) the body first.
  7. Below a visual demonstration of the steps.
    enter image description here
    Sideview makes it easier to select only the upper(shoulder) part. Important is to activate "X-Ray" Alt+Z to ensure the entire upper part is selected and not only the us facing part. Pressing P then allows for a separation based on "Selection"
  8. The new object will be the final cape(which we hide for now), the old cape becomes shoulders. And we are left with a hole at the bottom of the shoulders backside.
    enter image description here
    Face Orientation overlay active here to make the hole easier to see (red is inside)
  9. I would clean up the shoulder parts geometry for a cleaner look, quads and such, but it's not needed for the simulation asked. Closing the hole we end up with this.
    enter image description here
    The quads along the previous hole, will be used later as location for the pin-group of the cape.
  10. Since the shoulder part is done, we can switch to the cape geometry, as it needs some work before we can work with it. It's gonna be a bit more complicated, so i try to make small steps.
  11. First hide the shoulder part, then make the cape visible, select it and go in the vertex edit mode.
  12. We get rid of one side to reduce a lot of work. For that we go in the top view with Numpad 7 and activate x-ray with Alt+Z. enter image description here
  13. Then select all vertices on one side of the y-axis and press X Vertices.
    enter image description here
  14. Add a mirror modifier and select the Z-axis (situational, here it's Z).
    enter image description here
  15. At this point the cape is not usable for simulation, as it has very odd density. So we need to clean this up. Starting with making the cape single-layered. Going along the outer border of the cape, this edge selection needs to be made.
    enter image description here
    enter image description here
    We can see the cape as a 2 layered blanket, the outer is connected to the inner by a border, if we cut away at the border, the layers get structurally separated.
  16. With the border-loop selected we press X Vertices, to delete and at the same time separate the layers. With L (Select Linked) while hovering over a vertex of the left-over faces of the outer layer we select the now separate part(rest of the outer layer), which we then remove with X Vertices. A visual step by step demonstration below.
    enter image description here
  17. We are now left with only one layer of faces for the cape, which needs some cleanup, manually with more control, but more time spend here a visual demonstration of some (not all, as repetitive) steps.
    enter image description here
    The cleaned up and remeshed cape could look something like this.
    enter image description here
    Again, the settings for the Quad-remesher can be daunting, but results can be great
  18. The mesh having a better topology/density for cloth simulation makes the big difference. We now need to add the pin-group of the cape that will be responsible for fixing the cape to the shoulder-part.
    enter image description here
    it's possible to add some weight to the sides of the cape going down to stiffen them a bit enter image description here
    visible in weight paint mode, the selected vertices can be assigned a lower value which will be added to the active vertex-group
    enter image description here
  19. Back in object mode, we add the cloth simulation to the cape.
  20. Select the preset for silk and add the pin-group to the shape section.
    enter image description here
    the values are the ones that worked for me.
  21. Finally make the body a collision object. And for later usage it's a good idea to make the body the parent of the shoulders and the shoulders parent of the cape.(Ctrl+P object with the child and parent selected but the parent active)
    enter image description here
  22. Lastly as already visible in later pictures, add a floor below the princess and make it an collision object as well. Also, wind, nearly forgot ..
  23. The wind object was already in the scene, BUT it was too weak, and also not interesting enough, just like a hairdryer, on full throttle (still too weak).
  24. So we are setting up the wind like this:
    enter image description here
    steps should be easy to follow values can vary, but again these worked for me (may be a good starting point)

The final result can be dissected here Princess_with_cape (I didn't use Blend-exchange as original owner did not use it either, should i get the ok, i'll change to Blend-Exchange)

The cleanup steps i'm gonna add some more info later, hope in the meantime you can work with this.

Happy Blending

  • $\begingroup$ I actually have no words. I wish I could thank you in person, because this is genuinely fantastic. I'll work on this over the next couple days and I'll let you know if I have any questions. Thank you so much! $\endgroup$ – John May 10 '20 at 20:28
  • $\begingroup$ I have two quick questions, when separating the cape and shoulder parts, how do you do this, as they cannot be separated by P or selected with L individually. For steps 17 and 18, this deletes the vertices, so I am left with nothing in the view port, I'm not sure what you mean by outer and inner layers. $\endgroup$ – John May 11 '20 at 5:10
  • $\begingroup$ I updated the answer with more detailed steps and exchanged the pictures with gifs that show the steps in a more connected way. Specifically 7. and 15. Hope it's easier to understand now. Please check if it's answering your questions, should there still be unclear parts, don't hesitate to mention them. $\endgroup$ – Xylvier May 11 '20 at 12:29
  • $\begingroup$ Thank you! I just got it to work on my end with my armature and animation. I learned a lot from this, thank you very much. I hope this thread helps others who may be having similar problems, it's so in depth. $\endgroup$ – John May 12 '20 at 2:18
  • $\begingroup$ My pleasure. Would you kindly consider to accept the answer and may i ask if i can use Blend-Exchange service to share the file, so it's kept stored in the same system as the forum uses? $\endgroup$ – Xylvier May 12 '20 at 6:18

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