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Restrict a simulation influence node to the inside area of a peice of geo?

Message 1 of 10
636 Views, 9 Replies

Restrict a simulation influence node to the inside area of a peice of geo?

is there a way to (for example) add a turbulence noise to an aero sim but only winthin the area of another closed peice of geo.    Alternatively, how else might i achieve the goal of restricting an influence to a specific area in 3d space? 

Message 2 of 10

The extrude compound is using an influence. Maybe it does work similar to what you need.

Message 3 of 10
in reply to: mikeporetti

I believe mask_influence (which offers implicit shape or a geometric input) will produce what you need. You can daisy chain influence fields.



Message 4 of 10
in reply to: syracoj

perfect thank you!   is there a way to do this with source property?  it would be cool if there was a mask_source_property node 

Message 5 of 10
in reply to: mikeporetti

No there is not, but you can use a colorSet and paint where you want the influence of the source_property to go.

Message 6 of 10
in reply to: mikeporetti

There isn't a mask (with bounding box) functionality available for varying source properties.

But what I was able to put together was a means to paint color data based off of a (bounding) box geos bounds relation with the input object.


So where the box overlaps the input object we turn those verts/points white.


since this generates a color property we can plug that color prop into a vary_source and use it like a BBox "mask" for the vary_source node.


I'll post the compound and screen shots of the compounds internals after this post.



Message 7 of 10
in reply to: mikeporetti

how it works. 

top level input and outputs:




inside the compound: (sets set_geo_prop(color) based on array of black and white)




inside first iterate: (builds array of indices that are found inside the BBox bounds)




inside second iterate: (assigns black or white to a empty array. This does actual color assignment) 




compound attached


Message 8 of 10
in reply to: syracoj

this is awesome, studying it now, thanks! 

Message 9 of 10
in reply to: mikeporetti

your setup works great.   Ive used it to mask fog_density emission in an aero graph.   however i have been unable to connect it to a failure_stretch property in an mpm graph.


Is failure_stretch incompatible with color mask in vary_source_property?



Message 10 of 10
in reply to: mikeporetti

failure_stretch should work. There may be other properties at play to get a successful failure_stretch response. You may also want to negate the resulting color (so where it is white it becomes black, and where it is black it become white) and see the response then.

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