omnikopter Posted May 12, 2021 Share Posted May 12, 2021 Hi guys, A quick question from a Houdini beginner here. I'm working on a vellum simulation with wind force. It's a simple curtain animation but I'd like for the wind to be partially blocked by a wall (so only a part of the curtain is moving). I thought by default the wind is going to collide with my collision geometry but it doesn't seem to work that way. I've plugged a popwind node in the vellum solver - force_output but I'm not sure how to have that wind affected by an object. Do I need a pop solver somewhere? I'm attaching some screenshots from my scene. Thank you for the help! Quote Link to comment Share on other sites More sharing options...
underscoreus Posted May 12, 2021 Share Posted May 12, 2021 Hey! It is as you say, Houdini's forces don't really interact with collision geometry in that way. I think the easiest way to fix your issue is to make a point group in SOPS of the points you want the wind to affect and then add that group to the "group" parameter of your "popwind" node. Made a quick scene and it seems to be working. Hope that can help you solve your issue! 2 Quote Link to comment Share on other sites More sharing options...
omnikopter Posted May 13, 2021 Author Share Posted May 13, 2021 13 hours ago, underscoreus said: Hey! It is as you say, Houdini's forces don't really interact with collision geometry in that way. I think the easiest way to fix your issue is to make a point group in SOPS of the points you want the wind to affect and then add that group to the "group" parameter of your "popwind" node. Made a quick scene and it seems to be working. Hope that can help you solve your issue! Thank you for such a quick response! I've just tried that and seems to be working well, thanks! I've always struggled to get that effect in Marvelous Designer so happy to have it working in Houdini. I still wonder though if there's a more physically accurate way to do it... Anyways, thank you for the help again! 1 Quote Link to comment Share on other sites More sharing options...
underscoreus Posted May 13, 2021 Share Posted May 13, 2021 Glad I could help! 4 minutes ago, omnikopter said: I still wonder though if there's a more physically accurate way to do it... As for this, I can think of one way to do it "more" physically accurate but I'd say it's just not worth the extra effort since you'd probably lose more control and it would be a lot more work, but if you want to try it here is my thought: You could add the collision object as a collider in a pyro sim and simulate smoke blowing and colliding with the object, then export the velocity field from that simulation and bring that into the vellum simulation using the "popadvectbyvolumes" node. That way you'd get a "wind" that first has to "snake around" the collision object before touching the curtain. This is probably going to be somewhat difficult to control, at least compared to just making a group and having full control inside the "popwind" node, but then again, experimenting with stuff like this can be a lot of fun so why not! 1 Quote Link to comment Share on other sites More sharing options...
omnikopter Posted May 13, 2021 Author Share Posted May 13, 2021 4 hours ago, underscoreus said: Glad I could help! As for this, I can think of one way to do it "more" physically accurate but I'd say it's just not worth the extra effort since you'd probably lose more control and it would be a lot more work, but if you want to try it here is my thought: You could add the collision object as a collider in a pyro sim and simulate smoke blowing and colliding with the object, then export the velocity field from that simulation and bring that into the vellum simulation using the "popadvectbyvolumes" node. That way you'd get a "wind" that first has to "snake around" the collision object before touching the curtain. This is probably going to be somewhat difficult to control, at least compared to just making a group and having full control inside the "popwind" node, but then again, experimenting with stuff like this can be a lot of fun so why not! That does sound like a more accurate way to do it, but as you mentioned, probably more difficult to control. I'm actually quite happy with the result from the grouping method so will probably stick to that for now. Thanks again for help and different ideas!! lifesaver 1 Quote Link to comment Share on other sites More sharing options...
Librarian Posted May 18, 2021 Share Posted May 18, 2021 @omnikopter Maybe you gonna find Some tricks. vellumcurtain.hipnc Quote Link to comment Share on other sites More sharing options...
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