Is it possible to simulate aerodynamic lift generated by vellum patches moving in “air”? In C4D there is a little setup under soft body dynamics that emulates the effect of lift but I'm not sure how to do that with Vellum in Houdini.

Vellum uses aerodynamic Drag/Lift by default, it's calculated from Normal/Tangent Drag parameters defined for example by Vellum Constraints SOP and from the shape of the geometry

Thanks Tomas. So I increased the ratio between dragnormal and dragtangent attributes, but when I place a simple vellum patch in a simulation with gravity and a pop wind with air resistance only, as the patch gains speed it doesn't “fly”. I know the wind speed is zero from a simulation perspective but the idea is that the leading edge should start to get more “upwards” force(or at least in the direction of the normal so the patch eventually bends up like when you drop a piece of paper in air. I've randomized the dragnormal attributes across all points in the patch and added a bit of turbulence to force some twisting and therefore change the surface normal direction relative to the air but I don't see any lift happening. It just looks like the patch is floating down(diagonally sometimes due to the difference in drag ratios) but it never rises up against gravity.

here is an example at pretty much default settings

1. with some initial velocity against static wind
2. no initial velocity against directional wind

both result in lift against gravity

Thanks so much for the example Tomas. My problem is if you turn off the directed wind and just rely on air resistance the generate lift. So from the file you created, if you turn of the wind, you'll see that the vellum patch just falls down diagonally as it should. But that diagonal fall in real life would generate lift the moment the patch is out of shape and is not completely flat. So I try to add some deformation using some pop wind with noise and air resistance only. The result though is that the paper just “swims” down the same fashion but through a turbulent field. Ff course it is impacted aerodynamically by how the “wind” hits the surface normals but as you can see from my attached example building on your file, it never flies up for a little bit as it gains speed in the surface tangent direction, and that's what I meant by aerodynamic lift. I guess I should have clarified that I'm looking for a trick to fake the effect of the apparent wind on a non-uniform vellum surface.

For further clarity this is the effect I'm looking to emulate(sorry for the crude animation, but that's the only one I could find )

https://youtu.be/KOySP7FRmjw [youtu.be]

For what you want I suppose you'll have to create a medium for the airflow so that the paper has something to interact with.

Thank you all for the responses. I created a custom force to emulate Bernoulli's principle, where the patch's leading edge will “lift” up as it gets faster(assuming the edge is the leading edge relative to the direction of the velocity). It's obviously not perfect nor physically accurate (no airfoil calculations) but helps improve the realism of the flying paper simulations I have been working on.

I've attached the file here for reference in case someone wants to improve it further.