John Kunz
patreon
Balloon Bash
🕑 Added 2021-09-03 12:56:54 +0000 UTCI've been starting to experiment with cloth modeling using the Vellum solver. This is a bit similar to the Marvelous Designer workflow, where the fabric is laid flat and then sewn together during a simulation which allows the fabric to produce all the nice wrinkles, folds and bulges that make it feel real. In Houdini we have Vellum Drape node to replicate the Marvelous workflow https://www.sidefx.com/docs/houdini/nodes/sop/vellumdrape.html
In this setup, we simulate the drape (more of an inflate then a drape :D) of a foil mylar balloon. Both halves of the balloon are modeled and then stitch, weld, and pressure constraints are added. This is then fed into the Vellum Drape node which simulates the process of welding or sealing the balloon up and then inflating it (pressure). The result is a nice model of a foil balloon containing all the shiny wrinkles that give it the feel of helium.
You could use this inflated balloon model for set dressing a still life scene. In this case here, we simulate a continuous emission of balloons using the bullet RBD solver. As inflated balloons don't tend to bend or deform too much unless tons of force is applied, we can get away with using bullet to represent the balloons as rigid objects and simulate tons of balloons in near real-time.
For more complex situations, you could use Vellum to layer an additional cloth simulation on top of your already draped geometry to produce really nice looking fabrics, blankets, pillows, or other garments. More on this in the future ;)
Check out the Walkthrough Video on YouTube https://youtu.be/EQc7nosucBY
Scene File Attached
Comments
John Kunz
It should be points, this must've been a mistake I made. The vellum drape node has a "weld additional seams" toggle on the drape tab which is enabled and creating the actual welds across the seam points. I've attached an updated scene which should help clear this up, "balloon_drape_update.hiplc" In this case, I disabled the "weld additional seams" toggle, removed the stitch constraints nodes and changed the "target geometry" to points on the weld sides node. Sorry for the confusion, hopefully it makes more sense and is more straightforward in the updated file.
Carmen navarro
Nice tutorial! I've a question, why do you set 'target geometry' as primitives instead of points in the 'weld sides' node?
Chris Cousins
Great walkthrough thanks for this one. And the 'copy + transform pieces' trick at the end was sooo much simpler than the (embarassingly complicated, full of for-loops) setup I'd worked out -- really useful stuff.
absorbentghost
I'd really love to see more vellum stuff. Can u make art directable vellum related effects?Reacting to animated surfaces.Uvs and such.
Hussain Almossawi
Thanks John this is really cool!!
Iván Outeiral
thanks John! a lot of very interesting/useful stuff as always! <3
Kamil Pietrzak
thanks! sounds great, I will try but looks really serious :D
Kamil Pietrzak
https://www.dropbox.com/s/pbcs4ikdh5hfc3m/Screenshot_2.png?dl=0
Kamil Pietrzak
Oh yes! It's a lot lighter right now. Thank you! But.. another thing occurs. After importing to Blender I see all objects visible and freezed on the first frame. They will stay in that location until they should appear and move. For example: the 5th object will stay in that position until the 10th frame. Do you think that it can be on Houdini side? Or maybe Blender and I need to hide and unhide them manually?
John Kunz
Hey Kamil, it's hard to say without seeing your scene. Alembic isn't the best format for this as geometry is being emitted during the animation and Alembic doesn't like changing point counts. If you can separate the static geometry and export that as a separate file from the animated geometry it might help reduce the file size.
Kamil Pietrzak
Awesome stuff! I've a question: Based on your tutorial I made a similar scene and I wanted to export it to Blender as Alembic (.abc). The problem is that this file is now really big (~10GB) and Blender can't handle it. So, do you have any idea how to reduce file size? I tried to use the Clean node but it didn't help.
