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Advecting Pyro with Object (Help)

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Hey guys... 

So what I'm trying to do here is to make the skull go through the cloud and make it look somewhat natural but I can't get the effect I want 

I tried it two different ways and both give me crazy advection.... (also I don't know if is just a view port thing or the light, or the sim,  but the cloud also looks like id flickering) Anyway I'll attach the file and if anyone can give me some advice on how to do it better or if maybe I'm doing something the wrong way or missing anything I would really appreciate it!




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Hey Cristina, slightly complicated scene for an example

Also, skull geo will be helpful. You can lock any geo in the scene through a node's flag or a new cool 'stash' node

you don't need the static solver in the dop anymore

in the static object turn off object transform and make "obj path" parameter empty

a static object has an ability to grab vel from collision object, probably you don't need source volume

turbulence 100 is tooooo much

you don't have a temperature so buoyancy is useless


Edited by Deviner

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Have you tried doing a Trail SOP on the skull, converting to VDB w/velocity and sourcing in DOPs with a 'Source Volume" set to collision?

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I tried this but I don't know why I wasn't getting any collision, so I tried the regular static object. 

The collision is working.. but when I add turbulence it changes the entire cloud from frame 1, I was thinking on a way to make only the skull emit turbulence it that makes sense.. 

so have the skull and as it goes through the volume make only those parts of the volume have turbulence instead of the entire cloud, but I'm not sure how to approach this

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Hey Cristina,

So in regards to your question about masking the turbulence field. I've attached a scene file showing how to mask a turbulence field.

In the example I've built there are a few steps to get this working:

1) in dops you can use the 'gas match field' node to create a new field ('turbmask_custom') based on an existing field. In this case I first want to build the field that is going to be used for masking. (this is the initialization of the variable).
2) then I need to put a value inside the voxels of the newly created field, so I am using a source volume for this, but in the sop to dop bindings, the density field will put its value in the 'turbmask_custom' field instead of adding it to density.
3) the next step is to add the gasturbulence node to create a noise field, but in the control field tab we can specify the mask. So that is where I put 'turbmask_custom' and also set the control influence to 1 so 100% of my field is used.

In the case of your skull, ultimately you need a fog volume density field that contains those masking values. In the file I've added in a sphere to represent your skull. I first build an SDF from the sphere geo, then dilate the sdf, then turn it into a fog volume, then rename the field so it is not named 'surface' but instead is named 'density' so my sourcing in dops will be able to find the density field.

I've also turned on the velocity visualization in the pyro object so you can see what the velocity field is doing (especially visible if you turn on/off the control field on the gas turbulence).


You can get much more fancy by using dynamic fields that change over time (like temperature or heat, or some other custom field), but this should provide a good base example of masking a field in dops.
Good luck and definitely post back the results of your project when you're done with it!





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Thank you so much Peter! that was exactly what I was looking for 

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