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Q: Color Transfer to Volume (Isooffset)

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eitht
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Morning,

the image below shows color being transferred onto a box. A Scatter SOP using color as alternate attribute but it scatters on the surface, I want to use Isooffset SOP and scatter the points in a volume as VoronroiFracture would be used later.

I'm aware people are capable of coloring smoke within DOPs, can the same be done with Isooffset SOP.

Googling didnt produce any helpful threads, would be happy if someone can share links/solutions - Thankss!

eitht.

Attachments:
redbox.png (194.8 KB)

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fxrod
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You can ‘add’ color to your smoke in SOPs using the volume SOPs. If you're using the ‘Basic Smoke’ shader that comes with Houdini, you can name your volume ‘Cd’ and it'll pick up the color. Depends how you want to apply that color, of course.

One quick way for you to get the idea would be to add a Volume Ramp SOP to your volume in SOPs. Turn on ‘Use Color Ramp’. Then, change the ‘New Name’ to Cd. Apply your smoke shader and render.
Francisco Rodriguez
Effects Animator | Walt Disney Animation Studios
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fxrod
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However, my previous post doesn't solve your scatter problem. Seems you want to scatter points in the volume based on the color attribute?
Francisco Rodriguez
Effects Animator | Walt Disney Animation Studios
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eetu
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The question is a bit unclear to me as well. If you just want to scatter to the red parts of a volume, just plunk down a Scatter Sop and enter the number of the Cd.x volume (check the volume list with middle mouse) in the Group parameter.

Simple example attached.

Attachments:
red_vol_scatter.hip (85.5 KB)

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eitht
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Seems you want to scatter points in the volume based on the color attribute?

Yep Francisco, that's what i wanted. Still thanks for replying, i learned something from it!

eetu - that's a really neat example, i kind of understand the file. Tried to implement it with what i'm doing, appears i have to replace the “Volume SOP” with Color.* with the red color attribute via “AttribTransfer SOP”. I tried to import in my color attribute into “Volume VOP” but it didnt work.

Seems like it's wrong since i'm feeding in point attribute Cd, your example had like a Color Field (is that what it's called?).

eetu or anybody willing to look at my file? Thanks in advance!

eitht.

Attachments:
scatter_points_in_volume_with_color.hipnc (162.3 KB)

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eetu
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Here, hopefully I understood it better this time around

I fixed your nodetree, but I also made a simplified version with extra stuff removed, maybe you don't need all that.

Attachments:
eitht_scatter_points_in_volume_with_colore.hipnc (200.8 KB)

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eitht
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Yes, that's what I wanted!!!
Very thankful for the prompt reply!

Have doubts…

1) Volume from Attrib SOP, it transfers point attributes onto volume - is it transferring point position attributes here?


2) Volume from Attrib SOP, “Max Extrap Cells” - I can see what it's doing but honestly dont understand it after reading help doc.


3) Volume SOP, eetu you used it to turn the box into volume inorder to append it to the 1st input of Volume from Attrib SOP. I would think using Isooffset SOP would work but it didnt, why? :?


4) I needed some points to be scatters (see screen-cap, the red points) at the empty space, managed to do it the dirty way by subtracting the volume via Volume Mix SOP. Is there a better way to do this?


Sorry to bombard questions.
Here's the hip file incase someone didnt' get me.

eitht.

Attachments:
scatter_points_volume.hipnc (153.6 KB)
scatter.png (153.8 KB)

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