Hi there,

I've been trying to solve this problem (i.e. for a more complex scene showing a coronavirus merging with a host cell) for some time now, but with no success. Can any of you provide some help?

In its simplest form we have a sphere and a box (see attached hip file). The sphere is animated to pass into the top surface of the box. Both objects are converted to VDBs, VDB smoothed, then VDB converted back to surface(s). This results in the sphere descending and smoothly merging with the top surface of the box to create a single surface.

Points are then scattered onto the geometry (e.g. to be used later for instancing spike proteins onto the virus and other proteins on the host cell surface). The aim is to have all the points remain at fixed locations on the surfaces of the sphere and the box as they move towards each other and eventually merge.

The problem is that the scattered points change position from frame to frame. I believe this is because the resulting converted mesh(es) are constantly changing, which is forcing the scatter to re-assign the point positions.

I have tried various methods: timeshift + attributeinterpolate, or using a popnet to do effectively the same (as per this video https://www.youtube.com/watch?v=Jgtzb3VBJTM), but these methods don't seem to work as intended and the points still jump around on the surface(s).

Any assistance with this problem would be very much appreciated.

Thanks in advance.

Peter

Hi Peter
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Hi there,

Thanks for the link - much appreciated - some useful stuff there!

The volume gradient method almost works, except that the points on the sphere slide towards its upper pole as it descends. This is very similar to the results I was getting using the minpos in a popnet method (ref. https://www.youtube.com/watchv=Jgtzb3VBJTM).

Still open to further suggestions from people.

Cheers,
Peter