local winds?

[Truffi]

Hello,

Is it possible to limit the effect of forces only to certain designated areas?

For example:
-I generate a fire, that produces rising smoke.
-The smoke drifts away after it reaches a certain height - by the influence of wind.
-If I create the wind however, the whole cage is affected. The lower parts get blown away by the wind, too - even when the flames are surrounded by obstacle geometry, like a torus-shaped wall.
-A decay of the wind is no solution, since it's blowing from the side. What I'd like to do is create a zone of influence for the wind -regardless of it's pushing direction. I was thinking of the cascade effect as a work-around, but first wanted to ask - is there any straight solution to accomplish this in Phoenix?

Would be thankful for suggestions!

[Ivaylo Katev]

you can use the mapper helper. for example if you need wind in x direction, you have to put a gradient ramp map that is black in the lower part of the grid and red in the upper. the color is interpreted as vector, similar to the coloring of the tripod in the max viewports. red is x direction, green is y direction, blue is z direction. if you need negative values, use the output panel of the map and set negative multiplier.

[Raven]

Or use better wind.
http://rpmanager.com/plugins/BetterWind.htm

[Truffi]

thanks, however no matter what kind of map I assign, it always seems to drag down the smoke to negative Z, regardless of the colors I mapped to the PHXmapper.
as channel i used temperature. assigned velocity always caused all movement to freeze. I keep on trying..

[Ivaylo Katev]

the mapper affects the channel that is selected. to use it as wind, you have to affect the velocity, not the temperature. actually the mapper is an advanced tool, and it's hard to be used, i have a better idea, see the attached scene, it uses a non solid object in brush mode, that "involves" the air into its movement. there is a long box that is moving, and it is set to be a brush mode source (non solid object). the source is set weakly to affect the velocity (the discharge controls how strong to be the brush). the velocity multiplier is 10, to compensate the weak brush, i feel you wil ask - why we use weak brush and compensate this by big multiplier/ isn't possible to use strong brush (100% discharge)? i did exactly this and the effect was totally frozen simulation in the upper part of the grid. the strong brush just kills the simulation replacing the grid velocity with the velocity of the brush object.

[Truffi]

Yes, it works great. So this method will help me get there. Much appreciated!
I also tried assigning a swarm of Pflow Particles as a non-emitting brush source like you did with the box, which produced pretty cool effects. It only needs a way higher velocity multipler in order to influence the smoke.
Still, I would love to see the Phoenix Wrapper in action some time.

As for the Better Wind Tool: Thanks! It tried it and it definately seems handy for some situations when you want more control on the wind's fall-off.