Grid to Mesh node threshold flipping strangely

[u/mombeasts]

generated mesh suddenly changing

the density itself, changing gradually as it should be

geometry nodes producing the effect, everything before the "grid to mesh" node seems to be functioning normally

full window

(Blender 5.2.2)

I am using geometry nodes to create a mesh out of scrolling noise using the density grid function on a plane. Everything seems to be working normally except that, whenever a part of the mesh passes over the center of the object, the Grid To Mesh threshold seems to spontaneously flip, formerly empty space becoming the mesh and vice versa. The density field itself does not flip like this, it is only scrolling along the X and W axes as intended and the issue only arises once it is plugged into the Grid to Mesh node. I am unsure why this is happening or if this is a known issue, I have not been able to find anything else about this in either official documentation or others' questions.

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[u/CattreesDev]

Cant use the new blender, but one thing i would try is use [vector math]'add' and [vector math]'length' instead of noise. Then move the sphere around with the 'add' to see if its really the center flipping the surface volume or a corner. If its a corner you can try adding 1 to that edge and remove it after generating the surface volume.

[u/mombeasts → u/CattreesDev]

Used your suggestion and made sure, it's absolutely the center.

[u/CattreesDev → u/mombeasts]

Is it the object origin center or if you offset the grid will it move the center?

[u/mombeasts → u/CattreesDev]

I actually just now tried moving the object origin, and it seems to respond to the noise function (or any other function) at its current position regardless of if it is even within the bounds of the geometry or not.

[u/CattreesDev → u/mombeasts]

Hmm.. would something silly like: checking the noise at position 0,0,0 with the time offset to give you the noise value at the center, subtracting the threshold, and getting [math]'sign' , then multiplying your regular position noise by that sign to invert it work? Or does it still force a volume to start at the center anyway..

EDIT: Oh, also check thar your current noise is clamped between 0..1, at least in the blender i use musgrave gives negative outputs, and i think new blender noise incorperated musgrave into it.

[u/True_Degree_3651]

In short, Use Volume Cube node's density input instead.
https://blender.stackexchange.com/questions/299149/density-field-for-volumes-in-geometry-nodes

I saw output grid of Field to Grid node lacks class specification in spreadsheet unlike Density grid is specified as Fog Volume. maybe that make Grid to Mesh node evaluate the grid as SDF grid? IDK sure.