How to create a trail of stars under a flying carpet…?

[Kalleheikki Kannisto]

My first thought would be to use Particular, tracking the corners of the carpet by hand for a solid mask, then use that masked solid as a layer emitter.

Or use a 3D null to control the emitter position and manually track it to the motion of the carpet.

[Duca Simone luchini]

Hi Kalle,
many thanks for you reply.
I don’t need to tracker anything, cause I have perfect tracks of the corner of carpet imported from Cinema 4D.
What I didn’t understand about what you say is how to create and use a sold mask… please, may you be more specific?

THX!

[Duca Simone luchini]

Maybe do you mean to link trackers to the Mask vertex (of a Solid Layer) and then set the Solid layer as emitter?

[Kalleheikki Kannisto]

Particular has a layer emitter option, where layer opacity/transparency determines where the particles are emitted from, so my thought was to generate a masked solid (matching the carpet’s position) for a layer emitter so that the particles would original within that area. Since you can’t attach mask points to tracking points, you’d still have to animate (track) the mask corners by hand. I believe you would have to also additionally animate something like particle size to give it the appearance of moving in the z axis. You can’t really move the Particular layer if you do it this way, but make the Particular emitter a flat plane that fills the view.

The technique is described in detail here:
https://vimeo.com/79823940

BUT:

If you already have 3D tracked nulls, I would think you could average the nulls’ positions for the Particular emitter 3D position and then calculate the angle (if needed) from two (or four) corners’ positions.

[Kalleheikki Kannisto]

Another option that came to mind is to get it roughly right with Particular, eyeballing the Particular emitter into place, and then using animated mesh warp to make it follow the rug more precisely.

I’m certain that a magic carpet would bend and warp space-time 🙂

[Duca Simone luchini]

BUT:

If you already have 3D tracked nulls, I would think you could average the nulls' positions for the Particular emitter 3D position and then calculate the angle (if needed) from two (or four) corners' positions.

Yes, this is my case.
I copied the Position of my Null (it is the centre of the carpet track imported from Cinema 4D) to the Position of the solid Layer on which I applied Particular. But when the carpet rotates (It is taking off, rotating on itself), the emitter can’t to maintain the correct shape… I doesn’t rotate as it should, shortly as e 3d particle.

[Kalleheikki Kannisto]

Can you not manually keyframe the rotation values?

If the emitter is too hard to see you could conceivably make a 3D solid of the same dimensions and link the rotation values of your emitter to it so that you see what you are doing.