DForce item disappears during simulation
mdlark1966
Posts: 103
Hello all -
I am posing a G8F figure who is wearing the Mega Hoodie that can be found here in the marketplace. Her arms are kind of bent at odd angles, so I decided to add a dForce modifier and see if simulating it there would provide more realistic wrinkles. First, I encountered the problem that the hoodie won't stay closed. I dealt with that by simply using two hoodies on the figure - one with dForce and one without - and only showing the sleeves of the one that I added the modifier to, and vice versa for the other. While simulating, I leave the entire dforce hoodie visible, and hide everything else in the scene except for the base figure. I've used it this way a few times, and it works out fine.
But today I am working on a pose and simulation, and the dforce hoodie vanishes when I simulate. When I hit "render," the hoodie disappears. It just completely vanishes. If I try to clear the simulation, it reappears, but it's all twisted up and I have to reset the figure pose of the hoodie to get it back to normal.
I have not changed any parameters on either the hoodie itself or in the simulation settings - just using the default settings.
Anyone have any idea what might be happening here? Any advice would be very much appreciated. Thanks in advance!
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Comments
I've seen a similar problem with other items just disappearing when I attempt to simulate. I don't know a solution.
Does it have a (very) dense mesh? That will build up energy and in order to find a solution the item ends up far away.
If that is the case, I don't think there is a solution, as the mesh just don't can support sForce.
Reducing the offset value (Surfaces pane) so it is smaller than the typical edge-length may help in that case.
Oh, you are getting into the weeds here - maybe too much for my relatively limited skills at the moment. How do I determine if the mesh is "(very) dense"? And what offset value is considered "typical"?
I should also add that it isn't a case of the item going far away. I can focus the camera on it, and it simply isn't there. Or at least visually it isn't there.
I ran tests to try and understand what's causing this weird disappearing : a topology issue as too often with dForce related issues. dForce physics don't handle well polygons crossing one another and polygons with flipped normals attached to polygons with non flipped normals (inside / outside)
Problem : The inside of the hood has flipped normals. Edges are partially welded to the back from inside, but also partially to the front from outisde. That is just bad topology...
If this part of the hood had been flipped properly, and welded only to the front but not !! to the inside/back, dForce simulation would have worked just fine out of the box.
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- Delete polygons with wrong normals inside the hood. It looks less good without that extra thickness but at least it works.
- Add dForce dynamic to the hoodie Surfaces. Those values worked fine for me :
- define a dForce Modifier Weight Node to prevent the zipper and Rivets to move too much (weight at 0% or about 40% max on zipper and rivets).
Please don't post a modified version of a purchased product here or anywhere else. That would certainly be a EULA violation. Don't get yourself in trouble. Post your render of your results, though.
Damn, of course you're right. I spent all this time for nothing then ;)
Thanks for the heads up barbult. I removed the file and replaced it with explanations.
Viewport preview of the dForce fixed hoodie. Issue was juste those flipped polygons as I ran some tests and simulation or collisions with hair or fingers worked very well.
It looks excellent, except for the paper-thinness of the hood. The Thickener product does wonders to fix that. Do you have it?
Nope. Don't have the thickener. Indeed interesting. I tend to do modifications with apps more dedicated to modeling ;)
In this test I did yesterday to fix the OP issue, I decided to delete the hoodie's inside because it was the fastest solution. The best solution to keep thickness while still being able to simulate with dForce would be (have been) to select the same part of the hoodie I show in the first screenshot (Blender), and separate it rather than delete it. Then re-weld that part but ONLY the vertices from the front side, not those to the rear.
I'm sure simulation would also work just fine while still keeping a better hood shape. The Thickener could also do the trick although I fear it's just an equivalent of Blender's solidify modifier or 3DS Max shell modifier, so it would create a too sharp looking thickness with stretched UVs (last pixel of the texture stretched along the thickness).
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For issues such as this one on a cloth I didn't do myself, personal best solution is :
I export the DAZ cloth as obj. Import that in Marvelous Designer as garment ticking the option "trace 2D patterns from UV Map".
This way, I end up with the fabric as a 2D garment. And I have perfect control over anything that needs to be added or changed. I prefer to make my own clothes, but in the rush of some freelance contracts, using already made clothes and recreating them for a proper DAZ dForce simulation is the fastest way to finish a contract quickly ;)
Wow, thanks, Han!
Just curious - how did you keep the hoodie from "unzipping" during simulation? Mine falls open every time.
Only the slider is a separate mesh. If you don't want it to fall, select the Hoodie in the Scene Tab and add a dForce Weight Node :
Create > New dForce Modifier Weight Node
Select the dForce Modifier Weight Node in the Scene Tab, then use the Geometry Editor Tool (Alt+Shift+G) to select the slider (nothing more than a subdivided plane) and change Weight to 0 :
Node Weight Brush Tool (Alt+Shift+W) ; Right Click in the Viewport > Weight Editing > Fill Selected : 0
The rest of the so called Zipper is nothing more than a texture. The whole mesh is perfectly welded as you can see on this screenshot where I pulled the wireframe. Without someone editing the mesh in a 3D modeling app to separate both sides, there's absolutely no possible reason for it to "open". As it's not been modeled for that at all.
Just FYI I tried today to fix this hoodie by separating the inside of the hood and welding it only to the outside front. I thought it'd work but it does not. Mesh "disappears" again. Only solution seems to be my first test : deleting the inside. With any app that manages UV Islands, it's very simple to do. You could even do that with DAZ Geometry editor tool. Sadly there's no way to easily select parts by UVs in DAZ :/