Forums Technical Discussion Advecting "gradient" Field of Heightfield?

Advecting "gradient" Field of Heightfield?

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adamknauer1
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Hey guys wondering if anyone can give me some ideas to tackle this effect on a heightfield: https://twitter.com/Jose_Molfino/status/1669804412569567233 [twitter.com] The artist Jose says that it's a heightfield expanding inside a solver and a gradient field based on height is used for advection. Does anyone know how that works? How would you advect calculated values like gradient field vectors?

Thank you!
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animatrix_
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Hi,

Here is one way:

1. Compute grad using VEX in a Volume Wrangle:

v@grad = volumegradient ( 0, "height", @P );



2. Advect using Volume VOP SOP inside Solver SOP:



3. Run the simulation














You can also get different results by playing with the advection vector:

v@grad = volumegradient ( 0, "height", @P );
vector up = { 0, 1, 0 };
vector tangent = cross ( v@grad, up );

v@grad = tangent + v@grad;










v@grad = volumegradient ( 0, "height", @P );
vector up = { 0, 1, 0 };
vector tangent = cross ( v@grad, up );

v@grad = tangent;





Edited by animatrix_ - March 29, 2024 09:50:18

Attachments:
hfadvectx1.gif (2.5 MB)
hfadvectx2.gif (4.4 MB)
hfadvectx3.gif (2.8 MB)

Senior FX TD @ Industrial Light & Magic
Get to the NEXT level in Houdini & VEX with Pragmatic VEX! [www.pragmatic-vfx.com]

youtube.com/@pragmaticvfx | patreon.com/animatrix | pragmaticvfx.gumroad.com
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animatrix_
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You can also use an animated heightfield for the gradient to create more interesting variations like this:

Attachments:
hfadvectx4.gif (13.2 MB)

Senior FX TD @ Industrial Light & Magic
Get to the NEXT level in Houdini & VEX with Pragmatic VEX! [www.pragmatic-vfx.com]

youtube.com/@pragmaticvfx | patreon.com/animatrix | pragmaticvfx.gumroad.com
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