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Snappy_Darko

Basic Nodes Needed for UV preservation after Flip Fluid Sim

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The only tutorials I can find on preserving UV's after a flip fluid sim are for Houdini 16.0.  I'm running 16.5 and have struggled to get the procedure right.  SO far I have the Flip Fluid operation, then Convert to VDB (polygons?), then attribute transfer...however this doesn't really get me anywhere. If someone could list the string of nodes that I need i'd be really grateful.

 

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Posted (edited)

To preserve any attribute with a fluid sim you need to promote it to points before you sim. The point attributes should flow through the simulation without problem. You do have to add uv and Cd to the Keep attributes list on the fluidcompress node, or they will be removed from the points upon compression. The same is true for the Transfer Attributes list on the ParticleFluidSurface node. After surfacing attribute promote the uvs back to vertex.

You can go with the attribute transfer approach as well but you will need to extremely subdivide the source you are transferring from to get a reasonable match on the constructed fluid surface.

I explored the topic a little bit here.

You can also check out eetu's fluid image.

https://dailyhip.wordpress.com/2017/01/25/fluid-image/

 

Edited by Atom

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1 hour ago, Atom said:

To preserve any attribute with a fluid sim you need to promote it to points before you sim. The point attributes should flow through the simulation without problem. You do have to add uv and Cd to the Keep attributes list on the fluidcompress node, or they will be removed from the points upon compression. The same is true for the Transfer Attributes list on the ParticleFluidSurface node. After surfacing attribute promote the uvs back to vertex.

You can go with the attribute transfer approach as well but you will need to extremely subdivide the source you are transferring from to get a reasonable match on the constructed fluid surface.

I explored the topic a little bit here.

You can also check out eetu's fluid image.

https://dailyhip.wordpress.com/2017/01/25/fluid-image/

 

This all looks really promising, thank you.  I haven't used promote before, though ive seen it being used, just didn't know what it's purpose was.  

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Posted (edited)
On 8/4/2018 at 2:22 PM, Atom said:

To preserve any attribute with a fluid sim you need to promote it to points before you sim. The point attributes should flow through the simulation without problem. You do have to add uv and Cd to the Keep attributes list on the fluidcompress node, or they will be removed from the points upon compression. The same is true for the Transfer Attributes list on the ParticleFluidSurface node. After surfacing attribute promote the uvs back to vertex.

You can go with the attribute transfer approach as well but you will need to extremely subdivide the source you are transferring from to get a reasonable match on the constructed fluid surface.

I explored the topic a little bit here.

You can also check out eetu's fluid image.

https://dailyhip.wordpress.com/2017/01/25/fluid-image/

 

Hi Atom,  I've struggled to implement what you've suggested as im pretty new to Houdini.  But I found a video that may demonstrate would your talking about.  It's this:

 (the video is keyed to the time where he starts to promote points.)  My issue (besides the video being a bit disjointed and hard to follow), is that it's an old version of Houdini and the workflow is quite different in 16.5

I have perhaps a simpler question regarding this image: https://imgur.com/a/BFrwz39

Firstly, I don't want to create a sim, just an object from a single frame from the sim - which is what the image above shows.  However, I need to retain the shape and the UV's of image A for image B.  I need the UV's and the ID maps attached, so I can then texture the newly shaped object in substance painter. 

 

As I mentioned I pretty new to Houdini, so any suggestions please keep it basic (if possible).

 

Thanks

 

Edited by Snappy_Darko

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That method looks promising. It looks like the result is using the fluid sim points to point deform the original mesh. Then you don't have to worry about transferring Cd or UVs through the sim. They always reside on the original/deformed final mesh.

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It looks promising for sure, only here (4min52) he copies the colour parameter in pointvop, but doesn't say where (or if) he pastes it. I follow everything he does and get this https://imgur.com/a/iOidwJM (the colours are all wrong).  He's using version 15, maybe that's why?

 

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