[Sidefx-houdini-list] Billowy Smoke not "sticking" to Volume primitives

Francois-Xavier Boussard b.fx at free.fr
Fri Feb 27 01:53:07 EST 2009


Hello, 

Use a name sop to name existing volume data (If not named it will be interpreted as density by default), those data are stored in voxel (check volume primitive help). Iso surface, iso offset, primitve volume will create the volume itself (bounding box, division, initial data values). The volume mix help to modify the volume data . 

The rest position example from sesi use the isoSurface to create the the data as it allow you to use xzz position of each voxel as local variable ($X, $Y, $Z). Generate those values before any animation. As you want to stay at sop level you will use the name sop to give a name to those data. Volume data contain float values hence you have to generate three volume, give them name and merge them for render. 
Pipe your volume primitve into three IsoSurface as the box do in the sesi example. Take care to give the same division value as your primitive volume, channel link them is a good way to do it. Append a name sop to each of the isoSurface and set the name value to rest.x rest.y rest.z respectivly. 
Add a name sop to your primitive volume, set the name value to density and merge all the name sop together (plus the velocity name sop if you have some velocity) 

In the velocity example you where using an IsoOffsetSurface. The IsoOffsetSurface create inital data to 0 and 1. The volumemix is then an easy way to modify those values as it give you access to the local variable $V (values). 

cheers 
francois 

----- Mail Original ----- 
De: craigleehoffman at aol.com 
À: sidefx-houdini-list at sidefx.com, "b fx" <b.fx at free.fr> 
Envoyé: Jeudi 26 Février 2009 18:21:47 GMT +01:00 Amsterdam / Berlin / Berne / Rome / Stockholm / Vienne 
Objet: Re: [Sidefx-houdini-list] Billowy Smoke not "sticking" to Volume primitives 



Thanks! That is a good place to start. 

Still not sure how to apply this to a Volume Primitive, but it seems like I would do it the same way I added Velocity via the Name SOP and Volume Mix SOP. 


So anyone know if I add the rest.x attribute to my Volume via a Name SOP , do I just put $X in the Value field of the Volume Mix SOO with "Mix Method" as "User"? 

Thanks! 
-Craig 



-----Original Message----- 
From: Francois-Xavier Boussard <b.fx at free.fr> 
To: sidefx-houdini-list at sidefx.com 
Sent: Thu, 26 Feb 2009 8:18 am 
Subject: Re: [Sidefx-houdini-list] Billowy Smoke not "sticking" to Volume primitives 


Hello 

Check this example file, forget the dops part, the object named rest is what you 
want. 
In dops (was it 9.1 or 9.5 ...?) the rest position comes now  with the smoke 
object or the gaz rest pos but this is still a good example for Sop vector field 
:) 

http://www.sidefx.com/docs/houdini9.5/examples/nodes/dop/smokeobject/RestField 
you have it localy too 

cheers 
francois 


----- Mail Original ----- 
De: "David Johnson" < daveinengland at gmail.com > 
À: sidefx-houdini-list at sidefx.com 
Envoyé: Jeudi 26 Février 2009 16:40:32 GMT +01:00 Amsterdam / Berlin / Berne / 
Rome / Stockholm / Vienne 
Objet: Re: [Sidefx-houdini-list] Billowy Smoke not "sticking" to Volume 
primitives 

The Billowy Smoke likes to have a "rest" attribute on the volume. I'm not 
sure how to implement it for your setup, but see if you can use that to help 
your texture stick. 

Dave 

On Wed, Feb 25, 2009 at 1:13 PM, < craigleehoffman at aol.com > wrote: 

> 
> 
> 
> 
>  No- the volume shapes animate via a VolumeMix expression based on $LIFE, 
> etc. 
> 
> -c- 
> 
> 
> 
> 
> -----Original Message----- 
> From: Louis Dunlevy < louisdunlevy at gmail.com > 
> To: sidefx-houdini-list at sidefx.com 
> Sent: Wed, 25 Feb 2009 1:07 pm 
> Subject: Re: [Sidefx-houdini-list] Billowy Smoke not "sticking" to Volume 
> primitives 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Can you instance the volumes instead? Then your "object" space is going 
> to be very clear cut.. just a thought 
> 
> craigleehoffman at aol.com wrote: 
> > 
> > Haven't investigated this too much, but wondered if anyone had a quick 
> fix for 
> this. 
> > 
> > Basically I have a Copy SOP copying Volume Primitives onto moving 
> particles 
> and I noticed when adding the Billowy Smoke shader from the Material 
> Palette 
> that the Noise doesn't follow the Volumes as they moved.? I dove down into 
> the 
> Shader and set the "restpos" Node from "Texture" to "Object" and still no 
> dice. 
> > 
> > Since I am dealing with Volumes, is the proper thing to create new 
> Volumes for 
> x, y, & z Rest Position attributes like you do for motion blur velocity and 
> then 
> reference those attributes in the shader?? Or is there something easier? 
> > 
> > Thanks, 
> > Craig 
> > ? 
> > 
> > 
> > 
> > _______________________________________________ 
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> > Sidefx-houdini-list at sidefx.com 
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> > 
> > 
> 
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